Radiosurgery and Radiotherapy
12.3K views | +15 today
Follow
Radiosurgery and Radiotherapy
Your new post is loading...
Your new post is loading...
Scooped by Miguel Martín-Landrove
Scoop.it!

Hypofractionation & Positioning- (Relatively) New Approaches in Breast Cancer Radiation

MGMC Physician Grand Rounds, 11/30/16
John Hardie, MD, Radiation/Oncology
McFarland Clinic
more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Proton computed tomography using a 1D silicon diode array

Peng Wang, Jochen Cammin, Francesca Bisello, Timothy D. Solberg, James E. McDonough, Timothy C. Zhu, David Menichelli, Boon-Keng Kevin Teo

Med. Phys. 43, 5758 (2016);

Purpose:

Proton radiography (PR) and proton computed tomography (PCT) can be used to measure proton stopping power directly. However, practical and cost effective proton imaging detectors are not widely available. In this study, the authors investigated the feasibility of proton imaging using a silicon diode array.


Methods:

A one-dimensional silicon diode detector array (1DSDA) was aligned with the central axis (CAX) of the proton beam. Polymethyl methacrylate (PMMA) slabs were used to find the correspondence between the water equivalent thickness (WET) and 1DSDA channel number. Two-dimensional proton radiographs were obtained by translation and rotation of a phantom relative to CAX while the proton nozzle and 1DSDA were kept stationary. A PCT image of one slice of the phantom was reconstructed using filtered backprojection.


Results:

PR and PCT images of the PMMA cube were successfully acquired using the 1DSDA. The WET of the phantom was measured using PR data. The resolution and maximum error in WET measurement are 2.0 and 1.5 mm, respectively. Structures down to 2.0 mm in size could be resolved completely. Reconstruction of a PCT image showed very good agreement with simulation. Limitations in spatial resolution are attributed to limited spatial sampling, beam collimation, and proton scatter.


Conclusions:

The results demonstrate the feasibility of using silicon diode arrays for proton imaging. Such a device can potentially offer fast image acquisition and high spatial and energy resolution for PR and PCT.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

New prostate cancer treatment uses 'body GPS' technology

New prostate cancer treatment uses 'body GPS' technology | Radiosurgery and Radiotherapy | Scoop.it

By Lexy Hamilton-Smith

Queensland prostate cancer sufferers will try a new GPS system to track the position of their tumour during radiation treatment, in a breakthrough designed to avoid organ or tissue damage.

Patients at the Princess Alexandra Hospital will start undergoing treatment within days now that the new computer program, Calypso, has gone online.

Radiation oncologist Tanya Holt explained that unlike conventional radiation beam therapies, the Calypso beacon tracked tumours in real time and only allowed radiation to go through when the prostate was in range.

In current practice, the tumour is positioned before treatment, but it can move more than a centimetre due to coughing or digestion.

That means a radiation beam can hit healthy surrounding tissue instead of tumour, causing serious side-effects such as bowel or rectal problems or urinary incontinence.

Dr Holt said the Calypso could detect a millimetre of movement in any direction.

"If it does, it will switch the beam off and wait until the prostate moves back into the right position, or realign the beam and begin again," she said.

"The more accurate, the higher the dose you can deliver to the right area and with a more accurate treatment the more patients will be cured."

Three transponders, smaller than a grain of rice, are implanted into the prostate during the routine outpatient procedure.

Just like a GPS communicating with a satellite, the tracking system locks onto the transponder signal coming from the prostate and follows it throughout the treatment.

Treatment time is also reduced because the machine also does the X-rays and CT scans.


Calypso gives patients hope

Four Queenslanders will undergo the revolutionary treatment in early December.

Retired teacher David Evans, 79, is one of them.
David Evans, 79, will undergo the new treatment after his diagnosis earlier this year.
Photo: David Evans, 79, will undergo the new treatment after his diagnosis earlier this year.

He was diagnosed with prostate cancer earlier this year.

"I would be telling lies if I said I was not nervous," he said.

"I just hope it will be successful.

"I am quite happy to try out the new technology and I understand it will be safer."

One in five men in Australia are at risk of developing prostate cancer before the age of 85.

Those able to access the technology in Queensland do so at no cost, as all treatments are bulk-billed.

There is just one other beacon tracking system being used in Australia, which is in Melbourne.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Favorable local control from consolidative radiotherapy in high-risk neuroblastoma despite gross residual disease, positive margins, or nodal involvement

Matthew J. Ferris, Hasan Danish, Jeffrey M. Switchenko, Claudia Deng, Bradley A. George, Kelly C. Goldsmith, Karen J. Wasilewski, W. Thomas Cash, Mohammad K. Khan, Bree R. Eaton, Natia Esiashvili

International Journal of Radiation Oncology*Biology*Physics, 27 November 2016


Purpose

Radiotherapy (RT) has an established role in consolidative treatment of high-risk neuroblastoma. In addition to the standard 21.6 Gy delivered to the primary site following surgical resection, recent cooperative group guidelines incorporate a 14.4 Gy boost in the instance of residual gross disease. Here we report the influence of RT dose and surgical pathology variables on disease control and overall survival (OS) in patients treated at a single institution.


Methods

We conducted a retrospective study of 67 high-risk neuroblastoma patients who received RT as part of definitive management from January 2003 until May 2014.


Results

At a median follow-up of 4.5 years, 26 patients (38.8%) failed distantly; 4 of these patients also failed locally. One patient progressed locally without distant failure. Local control was 92.5% and total disease control was 59.5%. No benefit was demonstrated for RT doses over 21.6 Gy with respect to local relapse-free survival (LRFS) (p = 0.55), disease-free survival (DFS) (p = 0.22) or OS (p = 0.72). With respect to LRFS, DFS, and OS, no disadvantage was seen for positive lymph nodes on surgical pathology, positive surgical margins, or gross residual disease. Of the patients with gross residual disease, 75% (6/8) went on to have no evidence of disease at time of last follow-up, and the two patients that failed did so distantly.


Conclusions

Patients with high-risk neuroblastoma in this series maintained excellent local control, with no benefit demonstrated for radiation doses over 21.6 Gy, and no disadvantage demonstrated for gross residual disease following surgery, positive surgical margins, or pathologic lymph node positivity. Though the limitations of a retrospective review for an uncommon disease must be kept in mind, with small numbers in some of the subgroups, it seems that dose escalation should be considered only in exceptional circumstances.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Evaluation of a machine-learning algorithm for treatment planning in prostate Low-Dose-Rate brachytherapy

Alexandru Nicolae, Gerard Morton, Hans Chung, Andrew Loblaw, Suneil Jain, Darren Mitchell, Lin Lu, Joelle Helou, Motasem Al-Hanaqta, Emily Heath, Ananth Ravi


International Journal of Radiation Oncology*Biology*Physics, 27 November 2016


Purpose

This work presents the application of a machine learning (ML) algorithm to automatically generate high-quality, prostate Low-Dose-Rate (LDR) brachytherapy treatment plans. The ML algorithm can mimic characteristics of pre-operative treatment plans deemed clinically acceptable by brachytherapists. The planning efficiency, dosimetry and quality (as assessed by experts) of pre-operative plans generated using an ML planning approach was retrospectively evaluated in this study.


Methods & Materials

Pre- and post-implant treatment plans were extracted from 100 high-quality LDR treatments and stored within a training database. The ML algorithm matches similar features from a new LDR case to those within the training database to rapidly obtain an initial seed distribution; plans were then further fine-tuned using stochastic optimization. Pre-implant treatment plans generated by the ML algorithm were compared to brachytherapist (BT) treatment plans in terms of planning time (Wilcoxon rank sum, α = 0.05) and dosimetry (one-way ANOVA, α = 0.05). Qualitative pre-implant plan quality was evaluated by expert LDR radiation oncologists using a Likert scale questionnaire.


Results

The average planning time for the ML algorithm was 0.84 ± 0.57 min compared to 17.88 ± 8.76 min for the expert planner (p=0.020). Pre-implant plans were dosimetrically equivalent to the BT plans; the average prostate V150% was 4% lower for ML plans (p=0.002); although, not clinically significant. Respondents ranked the ML generated plans as equivalent to expert BT treatment plans in terms of target coverage, normal tissue avoidance, implant confidence, and the need for plan modifications. Respondents had difficulty differentiating between plans generated by a human or the ML algorithm.


Conclusions

Prostate LDR pre-implant treatment plans that have equivalent quality to plans created by brachytherapists can be rapidly generated using ML. The adoption of ML in the brachytherapy workflow is expected to improve LDR treatment plan uniformity, while reducing planning time and resources.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Stereotactic body radiation therapy (SBRT) for centrally located primary and recurrent non-small cell lung cancer (NSCLC): analysis of toxicity and local control

John Bowers, Nathan R. Bennion, Martin Richardson, Kelly Spencer, James Larner, Ronald Kersh

Journal of Radiation Oncology, pp 1–7, 2016


Purpose/objectives

Stereotactic body radiation therapy for centrally located lung tumors has been associated with increased risk of toxicity. A current study aims to evaluate tumor control and toxicity in large cohort of centrally located lesions.


Methods

Central location was defined as tumors within 2 cm of the bronchial tree, trachea, major vessels, esophagus, heart, pericardium, brachial plexus, or vertebral body. Tumors were biopsy proven or PET positive and included recurrent or primary non-small cell lung cancer (NSCLC). A dose was prescribed to a non-uniform planning target volume based on the internal tumor volume constructed from a 4D CT scan allowing for tumor motion. The treatment plans consisted of non-coplanar static aperture arcs and non-coplanar static fields. Treatments were delivered using 6MV X-rays with image guidance.


Results

At a median follow-up of 12.3 months, 107 total NSCLC tumors were retrospectively reviewed. A cohort consisted of primary (n = 57) and recurrent (n = 50) NSCLC tumors with subset of recurrent lesions including 27 hilar or mediastinal lymph nodes. Median and most frequent dose were 45 Gy in four fractions treated once weekly. Estimated 2-year Kaplan-Meier survival was 81.7%, with a significant survival advantage between primary and recurrent (p = 0.003). Eleven patients failed locally giving a 2-year actuarial local control rate of 80.7%, with control rates of 82.5 and 79.2% for primary and recurrent tumors, respectively (p = 0.828). Regional control at 2 years was not significantly different for primary (72.6%) and recurrent (62.7%). Analysis of toxicity revealed no grade 4 or 5 events. One grade 3 event was reported as pneumonitis. Grade 2 toxicity occurred in 10 patients, including dyspnea (1), chest wall pain (2), pneumonitis (4), rib fracture (1), and cough (2).


Conclusions

Moderate prescription dosing, treated once weekly, offers acceptable local control rates for centrally located tumors including recurrent mediastinal and hilar lymph nodes. Toxicity was minimal with the majority of patients experiencing no treatment-related adverse events.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Postmastectomy Radiotherapy: An American Society of Clinical Oncology, American Society for Radiation Oncology, and Society of Surgical Oncology Focused Guideline Update

Recht A, Comen EA, Fine RE, Fleming GF, Hardenbergh PH, Ho AY, Hudis CA, Hwang ES, Kirshner JJ, Morrow M, Salerno KE, Sledge GW Jr, Solin LJ, Spears PA, Whelan TJ, Somerfield MR, Edge SB


J Clin Oncol. 2016 Sep 19.


PURPOSE:

A joint American Society of Clinical Oncology, American Society for Radiation Oncology, and Society of Surgical Oncology panel convened to develop a focused update of the American Society of Clinical Oncology guideline concerning use of postmastectomy radiotherapy (PMRT).


METHODS:

A recent systematic literature review by Cancer Care Ontario provided the primary evidentiary basis. The joint panel also reviewed targeted literature searches to identify new, potentially practice-changing data.


RECOMMENDATIONS:

The panel unanimously agreed that available evidence shows that PMRT reduces the risks of locoregional failure (LRF), any recurrence, and breast cancer mortality for patients with T1-2 breast cancer with one to three positive axillary nodes. However, some subsets of these patients are likely to have such a low risk of LRF that the absolute benefit of PMRT is outweighed by its potential toxicities. In addition, the acceptable ratio of benefit to toxicity varies among patients and physicians. Thus, the decision to recommend PMRT requires a great deal of clinical judgment. The panel agreed clinicians making such recommendations for individual patients should consider factors that may decrease the risk of LRF, attenuate the benefit of reduced breast cancer-specific mortality, and/or increase risk of complications resulting from PMRT. When clinicians and patients elect to omit axillary dissection after a positive sentinel node biopsy, the panel recommends that these patients receive PMRT only if there is already sufficient information to justify its use without needing to know additional axillary nodes are involved. Patients with axillary nodal involvement after neoadjuvant systemic therapy should receive PMRT. The panel recommends treatment generally be administered to both the internal mammary nodes and the supraclavicular-axillary apical nodes in addition to the chest wall or reconstructed breast.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

High-Dose-Rate Brachytherapy for Localized Prostate Cancer: An Opportunity for Improvement over Intensity- Modulated Radiotherapy

Kim Y, Rockey WM

J Cancer Clin Res 2015;2(2): 1027

Advances in conformal radiotherapy techniques such as IG-IMRT have improved local tumor control and survival rates while decreasing GI and GU toxicities compared to 3D-CRT. However, the question remains if further dose escalation could improve the PSA relapse-free survival rate beyond 70% for highrisk patients? Treatment of high-risk patients using IG-IMRT remains challenging as these patients may present with occult distant disease. The potential benefits of high-dose rate (HDR) brachytherapy (BT) for localized prostate cancer are two folds: dose escalation to the target with possible boosting of the regions known to contain disease; and dose sparing to the urethra, bladder, rectum, and neuro-vascular bundles. Available clinical data for the use of HDR BT a boost or monotherapy confirm that HDR BT is capable of delivering a conformal, radiobiologically effective, very high radiation dose to the targeted tumor region without compromising gastrointestinal and genitourinary dose constraints. MRI-guided HDR BT potentially allows clinicians to deliver adaptive radiation to high-risk tumor subvolumes including the dominant intraprostatic legion, or even areas of recurrence. In addition, MRI-guided HDR offers a therapeutic advantage for those patients with visualized extra-capsular disease extension, as extra-capsular disease may be included in the radiation target volume.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Large scale retrospective Monte Carlo dosimetric study for permanent implant prostate brachytherapy

N. Miksys, E. Vigneault, A.G. Martin, L. Beaulieu, R.M. Thomson


International Journal of Radiation Oncology * Biology * Physics


Purpose

To retrospectively compare water-based and full tissue model Monte Carlo dose calculations in a large cohort of permanent implant prostate brachytherapy (PIPB) patients.


Methods and Materials

For 613 patients, EGSnrc BrachyDose dose calculations are performed in two virtual patient models: TG43sim (simulated AAPM TG-43 conditions) and MCref (CT derived heterogeneous tissue model with interseed effects). A sensitivity analysis is performed in a patient subset (25 with and 25 without prostatic calcifications) to explore dose calculation dependence on organ-at-risk (OAR) and calcification tissue elemental compositions and modelling approach.


Results

In the target volume, average D90 (V100) is lower with MCref than TG43sim by 5.9 ± 1.6% (2.6 ± 1.7%). Patients with prostatic calcifications can have substantial under-dosed volumes due to calcification shielding, lowering D90 up to 25%. In the urethra, average D5 (D30) is lower with MCref than TG43sim by 4.4 ± 1.8% (4.7 ± 1.9%). In the rectum (bladder) average D0.1cc is lower (higher) with MCref than TG43sim by 5.2 ± 1.8% (1.3 ± 1.8%). Doses to target and OARs can increase or decrease by several percent depending on the assumed tissue elemental composition. In patients with calcifications, differences between approaches to model calcifications can vary target and OAR dose metrics by upwards of 10%.


Conclusions

TG43sim typically overestimates target and OAR doses by several percent, on average, compared to MCref. The considerable variation in relative TG43sim and MCref doses between patients, and the larger dose differences for calcified patients, suggests that clinical adoption of Monte Carlo dose calculations for PIPB should be pursued. The substantial sensitivity of Monte Carlo dose calculations to patient modelling approach supports the adoption of a consensus modelling scheme, such as MCref described herein, to assure consistency of practice.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Is selective nodal irradiation in non-small cell lung cancer still safe when using IMRT? Results of a prospective cohort study

Hanneke M.A. Martinussen, Bart Reymen, Rinus Wanders, Esther G.C. Troost, Anne-Marie C. Dingemans, Michel Öllers, Ruud Houben, Dirk De Ruysscher, Philippe Lambin, Angela van Baardwijk

Radiotherapy and Oncology, 21 November 2016


Background and purpose

Isolated nodal failures (INF) are rare after 3D-conformal radiotherapy (3D-CRT) for stage III non-small cell lung cancer (NSCLC). Since incidental nodal irradiation doses are lower with Intensity Modulated Radiation Therapy (IMRT) than with 3D-CRT, INF may be higher after IMRT. We therefore investigated the incidence of INF after IMRT in stage III NSCLC patients.


Materials and methods

Stage III NSCLC patients undergoing radical radiotherapy using IMRT in the period January 2010 till March 2012 were included. The primary endpoint was the rate of INF, secondary endpoints included patterns of failure, progression free survival (PFS), overall survival (OS) and toxicity.


Results

183 stage III NSCLC patients were enrolled. With a median follow-up of 58.0 months 2.2% of patients had an INF. The median PFS was 15.0 months, the median OS 19.5 months. Patterns of recurrence: 2.2% INF, 11.5% local and 2.7% loco-regional recurrence, 26.8% distant metastases only, 18.0% a combination of local/loco-regional and distant metastases, and 38.3% patients without recurrence. One INF was out of field, in adjacent lymph nodes. Acute toxicity was limited.


Discussion

Selective nodal irradiation using IMRT in stage III NSCLC patients results in a low in-field incidence of INF (2.2%), similar to 3D-CRT, and may thus be considered safe.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Extremely hypofractionated radiation therapy shows promising toxicity results for intermediate risk prostate cancer patients

For men with intermediate risk prostate cancer, side effects at two years following radiation therapy (RT) were comparable for extremely-hypofractionated treatment, which was delivered in seven fractions across two and a half weeks, and conventional treatment of 39 fractions across eight weeks, according to research presented today at the 58th Annual Meeting of the American Society for Radiation Oncology (ASTRO).

The HYPO-RT-PC trial, a randomized multi-institutional phase III trial in Scandinavia, was designed to assess outcomes from highly accelerated extreme hypofractionation, which is delivered in smaller number of high doses -- seven fractions of 6.1 Gy each in this study.

“Randomized trials have confirmed the value of radiation dose escalation for prostate tumors, and the potential benefits of larger radiation doses in fewer fractions, are expected to increase the therapeutic efficacy for men with prostate cancer,” said Anders Widmark, MD, a professor of radiation sciences at Umeå University in Umeå, Sweden and lead author of the study. “Most of the existing data on hypofractionation, however, draws on cases of moderately accelerated radiation treatment of the prostate, in contrast to our study with more extreme hypofractionation. Our trial shows that patients experience similar side effects at two years with highly accelerated extremely hypofractionation.”

Twelve hundred men with intermediate risk prostate cancer were enrolled in the HYPO-RT-PC non-inferiority trial between 2005 and 2015. Eligible patients presented with tumor stages of T1c to T3a, prostate-specific androgen (PSA) levels of 20 or below, and one or two of three risk factors: stage T3a, a Gleason tumor score of seven or higher, or a PSA level greater than 10.

Patients were randomized to one of two treatment arms: the conventional fractionation group (CF) received 78 Gy of image-guided RT to the prostate in 39 treatments of 2 Gy each over eight weeks, and the extreme hypofractionation group (E-HF) received 42.7 Gy in seven treatments of 6.1 Gy each over two and a half weeks. Most patients (80 percent) received three-dimensional conformal RT (3-D CRT), and the remaining patients received volumetric arc therapy (VMAT). Androgen deprivation therapy was not allowed among study participants.

Primary outcomes included physician-reported side effects measured via a modified RTOG scale and patient-reported outcomes of urinary, bowel and sexual function side effects measured with the Prostate Cancer Symptom Scale (PCSS) questionnaire. Side effects were measured prior to RT start (baseline), at the end of RT, and at three, six, 12, 18 and 24 months following completion of RT. Median follow-up time from randomization for the entire patient population was 4.2 years, and findings reflect the 866 patients who reached two-year follow-up at the time of reporting in May 2016.

Men who received extremely hypofractionated RT in seven treatments experienced similar side effects two years following treatment as those who received conventional RT in 39 treatments. Rates of physician-reported grade 2+ toxicities at two years following treatment did not differ significantly between treatment arms. Urinary side effects were reported for 5.4 percent of E-HF patients and 4.6 of CF patients (p = 0.59). Bowel side effects were reported for 2.2 percent of E-HF patients and 3.7 of CF patients (p = 0.20). Impotence at two years post-treatment was reported in 34 percent of both groups, compared to 16 percent among all participants at baseline. Patient-reported outcomes at two years following treatment also did not differ significantly between treatment groups for overall bother from urinary (p = 0.17), bowel (p = 0.12) or sexual function (p = 0.71) symptoms.

Some modest but statistically significant differences emerged between the accelerated and conventional treatment arms in shorter-term bowel and urinary side effects. Acute urinary toxicity immediately following treatment was similar for both treatment groups (27.6 percent for E-HF vs. 22.8 percent for C-HF, p = 0.11), although acute bowel toxicity at the end of RT was higher for the accelerated E-HF treatment than for CF (9.4 vs. 5.3 percent; p = 0.023). Patient-reported bowel function at the end of RT was also significantly worse following E-HF than following CF for seven of 10 symptoms assessed, although these differences dissipated at three and six months follow-up. At one year post-treatment, patient-reported urinary function was significantly worse among E-HF patients for four of the 14 symptoms measured.

“The trial was designed to have equal late toxicity, so although there were some differences in shorter-term side effects, the results for long-term toxicity were precisely what we hoped to find,” said Dr. Widmark. “Our plan moving forward is to analyze primary endpoint data and present updated toxicity results approximately one year from now.”
more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

SRS With or Without WBRT and Cognitive Function in Patients With Brain Metastases

Paul D. Brown, Kurt Jaeckle, Karla V. Ballman, Elana Farace, Jane H. Cerhan, S. Keith Anderson, Xiomara W. Carrero, Fred G. Barker II, Richard Deming, Stuart H. Burri, Cynthia Ménard, Caroline Chung, Volker W. Stieber, Bruce E. Pollock, Evanthia Galanis, Jan C. Buckner, Anthony L. Asher

JAMA. 2016;316(4):401-409.

Importance Whole brain radiotherapy (WBRT) significantly improves tumor control in the brain after stereotactic radiosurgery (SRS), yet because of its association with cognitive decline, its role in the treatment of patients with brain metastases remains controversial.

Objective To determine whether there is less cognitive deterioration at 3 months after SRS alone vs SRS plus WBRT.

Design, Setting, and Participants At 34 institutions in North America, patients with 1 to 3 brain metastases were randomized to receive SRS or SRS plus WBRT between February 2002 and December 2013.

Interventions The WBRT dose schedule was 30 Gy in 12 fractions; the SRS dose was 18 to 22 Gy in the SRS plus WBRT group and 20 to 24 Gy for SRS alone.

Main Outcomes and Measures The primary end point was cognitive deterioration (decline >1 SD from baseline on at least 1 cognitive test at 3 months) in participants who completed the baseline and 3-month assessments. Secondary end points included time to intracranial failure, quality of life, functional independence, long-term cognitive status, and overall survival.

Results There were 213 randomized participants (SRS alone, n = 111; SRS plus WBRT, n = 102) with a mean age of 60.6 years (SD, 10.5 years); 103 (48%) were women. There was less cognitive deterioration at 3 months after SRS alone (40/63 patients [63.5%]) than when combined with WBRT (44/48 patients [91.7%]; difference, −28.2%; 90% CI, −41.9% to −14.4%; P < .001). Quality of life was higher at 3 months with SRS alone, including overall quality of life (mean change from baseline, −0.1 vs −12.0 points; mean difference, 11.9; 95% CI, 4.8-19.0 points; P = .001). Time to intracranial failure was significantly shorter for SRS alone compared with SRS plus WBRT (hazard ratio, 3.6; 95% CI, 2.2-5.9; P < .001). There was no significant difference in functional independence at 3 months between the treatment groups (mean change from baseline, −1.5 points for SRS alone vs −4.2 points for SRS plus WBRT; mean difference, 2.7 points; 95% CI, −2.0 to 7.4 points; P = .26). Median overall survival was 10.4 months for SRS alone and 7.4 months for SRS plus WBRT (hazard ratio, 1.02; 95% CI, 0.75-1.38; P = .92). For long-term survivors, the incidence of cognitive deterioration was less after SRS alone at 3 months (5/11 [45.5%] vs 16/17 [94.1%]; difference, −48.7%; 95% CI, −87.6% to −9.7%; P = .007) and at 12 months (6/10 [60%] vs 17/18 [94.4%]; difference, −34.4%; 95% CI, −74.4% to 5.5%; P = .04).

Conclusions and Relevance Among patients with 1 to 3 brain metastases, the use of SRS alone, compared with SRS combined with WBRT, resulted in less cognitive deterioration at 3 months. In the absence of a difference in overall survival, these findings suggest that for patients with 1 to 3 brain metastases amenable to radiosurgery, SRS alone may be a preferred strategy.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Counting Rate Characteristics and Image Distortion in Preclinical PET Imaging During Radiopharmaceutical Therapy

Emma Mellhammar, Magnus Dahlbom, Johan Axelsson, Sven-Erik Strand

J Nucl Med December 1, 2016 vol. 57 no. 12 1964-1970

PET may provide important information on the response during radiopharmaceutical therapy (RPT). Emission of radiation from the RPT radionuclide may disturb coincidence detection and impair image resolution. In this study, we tested the feasibility of performing intratherapeutic PET on 3 preclinical PET systems. Methods: Using 22Na point sources and phantoms filled with 18F, as well as a phantom filled with either 99mTc or 177Lu, we evaluated the coincidence counting rate and spatial resolution when both a PET and a therapeutic radionuclide were in the PET system. Because 99mTc has a suitable half-life and is easy obtainable, we used it as a substitute for a generic therapeutic radionuclide. Results: High activities of 99mTc deteriorated the coincidence counting rate from the 18F-filled phantom and the 22Na point source on all 3 systems. The counting rate could be corrected to a high degree on one of the systems by its dead-time correction. Spatial resolution was degraded at high 99mTc activities for all systems. On one of the systems, 177Lu increased the coincidence counting rate and slightly affected the spatial resolution. The results for high 177Lu activities were similar to those for 99mTc. Conclusion: Intratherapeutic imaging might be a feasible method of studying the response to RPT. However, some sensitive preclinical PET systems, unable to handle high counting rates, will have count losses and may also introduce image artifacts.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Silicon diode array lines up for proton CT

Silicon diode array lines up for proton CT | Radiosurgery and Radiotherapy | Scoop.it

Silicon diode detector arrays can be used for proton imaging – providing both fast image acquisition and high spatial and energy resolutions, report researchers from the US and Germany. Such detector arrays could be used to provide a low-cost and rapid measure of proton stopping powers for planning of proton treatments (Med. Phys. 43 5758).

X-ray CT is commonly used for proton therapy planning, but uncertainties caused by both the conversion of Hounsfield units to proton relative stopping power and the beam hardening effect of the CT scanner necessitate the addition of a 2.5–3.5% margin to both edges of the spread-out Bragg peak. This margin detracts from one of proton therapy's key advantages – the sparing of healthy tissue by ensuring that the proton beam's Bragg peak is contained within the target volume.

An alternative approach for planning lies in directly measuring the anatomic distribution of the proton relative stopping power, using proton imaging techniques such as 2D proton radiography or 3D proton CT. While medical proton delivery systems have reached an advanced level of development, corresponding imaging technologies have been relatively under-investigated – and there is a need to develop practical and cost-effective proton imaging detectors.

Systems currently under development can be categorized as either tracking or integrating type detectors. Tracking imagers use two detector arrays and a calorimeter to measure individual proton trajectories and residual energy – but are incompatible with passive scattered proton beams and have a slow image acquisition speed that makes them impractical for clinical use.

In contrast, integrating systems are compatible with both pencil-beam scanning and passive scattered proton beams – making the image acquisition time short enough for clinical use. While a number of such detectors have been proposed, all have had significant limitations – for example, plastic nuclear track detectors require an unsuitable wet chemistry developing process, while CCD camera and scintillator detectors come with a relatively low energy resolution, as do stacked CMOS sensors.

In their new study, Peng Wang – of the Texas Center for Proton Therapy – and colleagues report a prototype detector design with a one-dimensional silicon diode detector array that was originally developed for measuring planar photon dose distributions. The detector is composed of four monolithic silicon sensor modules – each of which is 64 mm in length and comprises 64 pixels. When placed along the central axis of the proton beam, the position of the beam's Bragg peak along the diode array correlates with the water equivalent thickness (WET) of the object being imaged.
www.versahd.com

"The design has the potential to have a very high spatial resolution – in the x–y direction – and energy resolution – in the z direction – since the size of diodes can be made quite small," said Wang. The researchers tested the detector with a block phantom made of polymethyl methacrylate slabs, of known WET, which were designed to calibrate the prototype and assess its spatial and contrast resolution.

By moving the phantom relative to the proton beam axis, the researchers produced a proton radiography image of the phantom; the resolution and maximum error in WET measurements were found to be 2.0 and 1.5 mm, respectively. They also reconstructed a proton CT slice using filtered backprojection, with the resultant image showing good agreement with simulation – clearly resolving slits in the phantom down to the 2 mm scale.

"There is increasing interest in proton radiography and proton CT as 2D tools for range and dosimetry verification in adaptive proton therapy," comments Reinhard Schulte, a medical physicist from Loma Linda University who was not involved in this study. He adds that the new detector design is a low-cost solution that "could find its way into clinical application much sooner than the more technologically demanding solutions based on individual proton tracking and analysis".

Having demonstrated the feasibility of their approach, Wang and colleagues are now looking to build and calibrate a complete prototype detector as the next step towards commercialization and clinical application.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

External Validation and Optimization of International Consensus Clinical Target Volumes for Adjuvant Radiation in Bladder Cancer

Abhinav V. Reddy, John P. Christodouleas, Tianming Wu, Norman D. Smith, Gary D. Steinberg, Stanley L. Liauw

International Journal of Radiation Oncology*Biology*Physics, 27 November 2016


Purpose

International Consensus (IC) clinical target volumes (CTVs) have been proposed to standardize radiation field design in the treatment of patients at high risk for local regional failure (LRF) after radical cystectomy. The purpose of this study was to externally validate the IC CTVs in a cohort of post-surgical patients followed for LRF, and identify revisions that might improve its performance.


Methods

/Materials: Of 334 patients with pT3-4 bladder cancer treated with radical cystectomy, 58 (17%) developed LRF, of which 52 had CTs available for review. Images with LRF were exported into a treatment planning system, and IC CTVs were contoured and evaluated for adequacy of coverage of each LRF, with respect to both the patient and each of six pelvic subsites: common iliac (CI), obturator region (OR), external and internal iliac (EI/II), presacral (PS), cystectomy bed (CB), or other pelvic site. Revisions to the IC contours were proposed based on the findings.


Results

Of the 52 patients with documented LRF, 13 (25%) patients had LRFs that were outside of the IC CTV involving 17 pelvic subsites: 5 near the CI CTV, 5 near the OR CTV, 1 near the EI/II, and 6 near the CB. The 5 CI failures were located superior to the CTV and the 5 OR failures were located medial to the CTV. Increasing the superior boundary of the CI to a vessel-based definition of the aortic bifurcation, and increasing the medial extension of the OR by an additional 9 mm, decreased the rate of patients with LRF outside of the IC CTV to 7 (13%) patients.


Conclusion

“Modified IC CTVs” inclusive of a slight adjustment superiorly for the common iliac region, and medially for the obturator region, may reduce the risk for pelvic failure in patients treated with adjuvant radiation therapy.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Preoperative Accelerated Partial Breast Irradiation for Early-Stage Breast Cancer: Preliminary Results of a Prospective Phase II Trial

Elizabeth Nichols, Susan B. Kesmodel, Emily Bellavance, Cynthia Drogula, Katherine Tkaczuk, Randi J. Cohen, Wendla Citron, Michelle Morgan, Paul Staats, Steven Feigenberg, William F. Regine


International Journal of Radiation Oncology*Biology*Physics, 27 November 2016


Introduction

Assess the feasibility of utilizing 3D conformal APBI in the pre-operative setting followed by standard breast conserving therapy.


Methods and Materials

This is a prospective trial testing the feasibility of pre-operative APBI followed by lumpectomy for patients with early stage invasive ductal breast cancer. Eligible patients had T1-T2 (< 3 cm), N0 tumors Patients received 38.5 Gray (Gy) in 3.85 Gy fractions delivered twice daily. Surgery was performed > 21 days after radiotherapy. Adjuvant therapy was given as per standard of care.


Results

Twenty-seven patients completed treatment. With a median follow up of 3.6 years (range: 0.5 - 5 years), there have been no local or regional failures. A complete pathologic response based on hematoxylin and eosin stains was seen in 4 patients (15%). There were four grade 3 seromas. Patient reported cosmetic outcome was rated as good to excellent in 79% of patients following treatment.


Discussion

Pre-operative 3DCRT-APBI is feasible and well tolerated in select patients with early stage breast cancer with no reported local recurrences and good-excellent cosmetic results.


Conclusion

The pathologic response rates associated with this non-ablative APBI dose regimen are particularly encouraging and support further exploration of this paradigm.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Dosimetric Implications of Residual Tracking Errors during Robotic SBRT of Liver Metastases

Mark Chan, Melanie Grehn, Florian Cremers, Frank-Andre Siebert, Stefan Wurster, Stefan Huttenlocher, Jürgen Dunst, Guido Hildebrandt, Achim Schweikard, Dirk Rades, Floris Ernst, Oliver Blanck

International Journal of Radiation Oncology*Biology*Physics, 27 November 2016


Purpose

While the metric precision of robotic stereotactic body radiation therapy (SBRT) in the presence of breathing motion is widely known, we investigated the dosimetric implications of breathing phase-related residual tracking errors.


Methods

and Material: From 24 patients (28 liver metastases) treated with the CyberKnife we recorded the residual correlation, prediction, and rotational tracking errors from 90 fractions and binned them into ten breathing-phases. The average breathing phase errors were used to shift and rotate the CTV/PTV for each phase to calculate a pseudo 4D error dose distribution for comparison with the original planned dose distribution.


Results

The median systematic directional correlation, prediction, and absolute aggregate rotation errors were 0.3mm (0.1–1.3mm), 0.01mm (0.00–0.05mm), and 1.5° (0.4°–2.7°). Dosimetrically, 44%, 81%, and 92% of all voxels differed less than 1%, 3%, and 5% of the planned local dose. Median coverage reduction for the PTV was 1.1% (-7.8%–+0.8%), significantly depending on correlation (p=0.026) and rotational (p=0.005) error. With a 3mm PTV margin, the median coverage change for the CTV was 0.0% (-1.0%–+5.4%), not significantly depending on any investigated parameter. In 42% of patients, the 3mm margin did not fully compensate for the residual tracking errors, resulting in a CTV coverage reduction of 0.1%–1.0%.


Conclusions

For liver tumors treated with robotic SBRT, a safety margin of 3mm is not always sufficient to cover all residual tracking errors. Dosimetrically, this translates only into small CTV coverage reductions.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Novel biomarker identification using metabolomic profiling to differentiate radiation necrosis and recurrent tumor following Gamma Knife radiosurgery

Alex Y. Lu, Jack L. Turban, Eyiyemisi C. Damisah, Jie Li, Ahmed K. Alomari, Tore Eid, Alexander O. Vortmeyer, Veronica L. Chiang

Journal of Neurosurgery, November 25, 2016

OBJECTIVE

Following an initial response of brain metastases to Gamma Knife radiosurgery, regrowth of the enhancing lesion as detected on MRI may represent either radiation necrosis (a treatment-related inflammatory change) or recurrent tumor. Differentiation of radiation necrosis from tumor is vital for management decision making but remains difficult by imaging alone. In this study, gas chromatography with time-of-flight mass spectrometry (GC-TOF) was used to identify differential metabolite profiles of the 2 tissue types obtained by surgical biopsy to find potential targets for noninvasive imaging.


METHODS

Specimens of pure radiation necrosis and pure tumor obtained from patient brain biopsies were flash-frozen and validated histologically. These formalin-free tissue samples were then analyzed using GC-TOF. The metabolite profiles of radiation necrosis and tumor samples were compared using multivariate and univariate statistical analysis. Statistical significance was defined as p ≤ 0.05.


RESULTS

For the metabolic profiling, GC-TOF was performed on 7 samples of radiation necrosis and 7 samples of tumor. Of the 141 metabolites identified, 17 (12.1%) were found to be statistically significantly different between comparison groups. Of these metabolites, 6 were increased in tumor, and 11 were increased in radiation necrosis. An unsupervised hierarchical clustering analysis found that tumor had elevated levels of metabolites associated with energy metabolism, whereas radiation necrosis had elevated levels of metabolites that were fatty acids and antioxidants/cofactors.


CONCLUSIONS

To the authors' knowledge, this is the first tissue-based metabolomics study of radiation necrosis and tumor. Radiation necrosis and recurrent tumor following Gamma Knife radiosurgery for brain metastases have unique metabolite profiles that may be targeted in the future to develop noninvasive metabolic imaging techniques.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

[Use of hypnosis in radiotherapy as an alternative to general anesthesia in pediatric radiation oncology]

Claude L, Morelle M, Mancini S, Duncan A, Sebban H, Carrie C, Marec-Berard P

Bull Cancer. 2016 Nov 11.

BACKGROUND: General anesthesia (GA) is often needed for radiotherapy (RT) in young children. This study aimed to evaluate the place of the rituals and/or hypnosis in pediatric in a reference center in pediatric radiation oncology in Rhône-Alpes Auvergne.

METHODS: This observational study retrospectively collected data on AG in children<5 years treated by RT in Leon-Berard regional center, Lyon, France between 2003 and 2014. Two-time periods, before and after 2008 have been compared, the second one introducing accompaniment methods such as hypnosis systematically. Explanatory analyses of AG were performed using logistic regression.

RESULTS: One hundred and thirty-two children benefited from RT in that period and were included (70 patients until 2008, 62 after 2008). Fifty-three percent were irradiated under GA. There was significant reduction (P<0.1) in the use of GA after 2008. The use of GA was not significantly associated with the RT techniques. The patients more likely to undergo RT without GA were the oldest and the patients treated for abdominal lesions (P<0.01).

DISCUSSION: The study confirms that rituals and hypnosis can be used instead of GA in about half of patients under 5 years, even also with high-technicity RT requiring optimal immobilization.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Calypso System

The prostate can move during radiation treatment as a result of breathing or movement in the intestines. Radiation oncologists tend to enlarge the treatment area to make sure the moving prostate is irradiated. By doing this, healthy tissue near the prostate may also be affected by the radiation, leading to a high rate of urinary, bowel and sexual side effects. The Calypso 4D Localization System uses an advanced treatment method to deliver focused doses of radiation with greater accuracy to prostate cancer patients receiving external beam radiation therapy. Also known as “GPS for the Body”, this technology continuously tracks movement of the prostate in real time and concentrates radiation to the tumor. Prior to this treatment, ultrasound guidance is used to implant three electromagnetic Beacon transponders, each about the size of a grain of rice, into the prostate through the rectum. The 4D electromagnetic array sends signals to the implanted transponders for activation. In turn, the transponders then send out safe radiofrequency waves that communicate with the Calypso machine. This gives the physician the ability to track the prostate motion to sub-millimeter accuracy during radiation treatment. By targeting cancer cells and avoiding nearby healthy tissues, Calypso protects the bladder, colon and other critical healthy tissue. By using this technology, common side effects of radiation treatment for prostate cancer, such as incontinence and erectile dysfunction, may be greatly minimized. Calypso is currently FDA approved for use in the treatment of prostate cancer and many other cancers, except lung.
more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

*ASCENDE-RT: An Analysis of Survial Endpoints for a Randomized Trial Comparing a Low-Dose-Rate Brachytherapy Boost to a Dose-Escalated External Beam Boost for High- And Intermediate-Risk Prostate C...

W. James Morris, Scott Tyldesley, Sree Rodda, Ross Halperin, Howard Pai, Michael McKenzie, Graeme Duncan, Gerard Morton, Jeremy Hamm


International Journal of Radiation Oncology * Biology * Physics, 2016


Purpose

To report the primary endpoint of biochemical progression free survival (b-PFS) and secondary survival endpoints for a randomized trial comparing two methods of dose escalation for intermediate- and high-risk prostate cancer.


Materials and Methods

The trial enrolled 398 men, median age 68; 69% (N =276) had high-risk disease. After stratification by risk group, subjects were randomized to either a standard arm with 12 months of androgen deprivation therapy (ADT), pelvic irradiation to 46 Gy followed by a dose-escalated external beam radiation therapy (DE-EBRT) boost to 78 Gy, or an experimental arm that substituted a low-dose-rate prostate brachytherapy (LDR-PB) boost. Two hundred trial subjects were assigned to DE-EBRT boost and 198 to LDR-PB boost. Median follow-up is 6.5 years.


Results

In an intent-to-treat analysis, men randomized to DE-EBRT were twice as likely to experience biochemical failure (MVA HR: 2.04, p =0.004). The 5-, 7-, and 9-year Kaplan-Meier b-PFS estimates were 89%, 86% and 83% for those randomized to LDR-PB boost versus 84%, 75% and 62% for DE-EBRT boost (log rank p <0.001). The LDR-PB boost benefited both intermediate- and high-risk patients. Since the b-PFS curves for the treatment arms diverge sharply after 4 years, the relative advantage of the LDR-PB should increase with longer follow up.

In MVA, the only variables correlated with reduced overall survival (OS) were age (MVA HR: 1.06/year, p =0.004) and biochemical failure (MVA HR: 6.30, p <0.001). Although biochemical failure was associated with increased mortality and randomization to DE-EBRT doubled the rate of biochemical failure, no significant OS difference was observed between arms (MVA HR 1.13, p =0.62).


Conclusions

Compared to 78 Gy EBRT, men randomized to LDR-PB boost were twice as likely to be free of biochemical failure at 6.5 years median follow-up.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Bone Marrow-Sparing Intensity Modulated Radiation Therapy with Concurrent Cisplatin for Stage Ib-Iva Cervical Cancer: An International Multi-Center Phase Ii Clinical Trial (Intertecc-2)

Loren K. Mell, Igor Sirák, Lichun Wei, Rafal Tarnawski, Umesh Mahantshetty, Catheryn M. Yashar, Michael T. McHale, Ronghui Xu, Gordon Honerkamp-Smith, Ruben Carmona, Mary Wright, Casey W. Williamson, Linda Kasaová, Nan Li, Stephen Kry, Jeff Michalski, Walter Bosch, William Straube, Julie Schwarz, Jessica Lowenstein, Steve B. Jiang, Cheryl C. Saenz, Steve Plaxe, John Einck, Chonlakiet Khorprasert, Paul Koonings, Terry Harrison, Mei Shi, A.J. Mundt


International Journal of Radiation Oncology * Biology * Physics


Purpose

To test the hypothesis that intensity modulated radiation therapy (IMRT) reduces acute hematologic and gastrointestinal (GI) toxicity for patients with locoregionally advanced cervical cancer.


Methods

We enrolled patients with stage IB-IVA cervical carcinoma on a single-arm phase II trial involving eight centers internationally. All patients received weekly cisplatin concurrently with once-daily IMRT, followed by intracavitary brachytherapy as indicated. The primary endpoint was the occurrence of either acute grade ≥ 3 neutropenia or clinically significant GI toxicity within 30 days of completing chemoradiotherapy. A pre-planned subgroup analysis tested the hypothesis that positron emission tomography (PET)-based image-guided IMRT (IG-IMRT) lowers the risk of acute neutropenia. We also longitudinally assessed changes in quality of life.


Results

From October 2011 to April 2015, 83 patients met eligibility criteria and initiated protocol therapy. Median follow-up was 26.0 months. The incidence of any primary event was 26.5% (95% CI, 18.2-36.9%), significantly lower than the 40% incidence hypothesized a priori from historical data (p=0.012). The incidences of grade ≥ 3 neutropenia and clinically significant GI toxicity were 19.3% (95% CI, 12.2-29.0%) and 12.0% (95% CI, 6.7-20.8%), respectively. Compared to patients treated without IG-IMRT (N=48), patients treated with IG-IMRT (N=35) had significantly lower grade ≥ 3 neutropenia (8.6% vs. 27.1%, 2-sided chi-square p=0.035), and non-significantly lower grade ≥ 3 leukopenia (25.7% vs. 41.7%, p=0.13) and any grade ≥ 3 hematologic toxicity (31.4% vs. 43.8%, p=0.25).


Conclusion

IMRT reduces acute hematologic and GI toxicity compared to standard treatment, with promising therapeutic outcomes. PET-guided IMRT reduces acute neutropenia.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Comparing conventional radiotherapy with stereotactIc body radiotherapy in patients with spinal metastases: study protocol for an randomized controlled trial following the cohort multiple randomize...

Joanne M. van der Velden, Helena M. Verkooijen, Enrica Seravalli, Jochem Hes, A. Sophie Gerlich, Nicolien Kasperts, Wietse S. C. Eppinga, Jorrit-Jan Verlaan, Marco van Vulpen

BMC Cancer 201616:909

Background

Standard radiotherapy is the treatment of first choice in patients with symptomatic spinal metastases, but is only moderately effective. Stereotactic body radiation therapy is increasingly used to treat spinal metastases, without randomized evidence of superiority over standard radiotherapy. The VERTICAL study aims to quantify the effect of stereotactic radiation therapy in patients with metastatic spinal disease.


Methods/design

This study follows the ‘cohort multiple Randomized Controlled Trial’ design. The VERTICAL study is conducted within the PRESENT cohort. In PRESENT, all patients with bone metastases referred for radiation therapy are enrolled. For each patient, clinical and patient-reported outcomes are captured at baseline and at regular intervals during follow-up. In addition, patients give informed consent to be offered experimental interventions. Within PRESENT, 110 patients are identified as a sub cohort of eligible patients (i.e. patients with unirradiated painful, mechanically stable spinal metastases who are able to undergo stereotactic radiation therapy). After a protocol amendment, also patients with non-spinal bony metastases are eligible. From the sub cohort, a random selection of patients is offered stereotactic radiation therapy (n = 55), which patients may accept or refuse. Only patients accepting stereotactic radiation therapy sign informed consent for the VERTICAL trial. Non-selected patients (n = 55) receive standard radiotherapy, and are not aware of them serving as controls. Primary endpoint is pain response after three months. Data will be analyzed by intention to treat, complemented by instrumental variable analysis in case of substantial refusal of the stereotactic radiation therapy in the intervention arm.


Discussion

This study is designed to quantify the treatment response after (stereotactic) radiation therapy in patients with symptomatic spinal metastases. This is the first randomized study in palliative care following the cohort multiple Randomized Controlled Trial design. This design addresses common difficulties associated with classic pragmatic randomized controlled trials, such as disappointment bias in patients allocated to the control arm, slow recruitment, and poor generalizability.

more...
No comment yet.
Scooped by Miguel Martín-Landrove
Scoop.it!

Gated Volumetric-Modulated Arc Therapy vs. Tumor-Tracking CyberKnife Radiotherapy as Stereotactic Body Radiotherapy for Hepatocellular Carcinoma: A Dosimetric Comparison Study Focused on the Impact...

Gated Volumetric-Modulated Arc Therapy vs. Tumor-Tracking CyberKnife Radiotherapy as Stereotactic Body Radiotherapy for Hepatocellular Carcinoma: A Dosimetric Comparison Study Focused on the Impact... | Radiosurgery and Radiotherapy | Scoop.it

KyoungJun Yoon, Jungwon Kwak, Byungchul Cho, Jin-hong Park, Sang Min Yoon, Sang-wook Lee, Jong Hoon Kim

PLOS ONE, November 22, 2016

Purpose

To assess the potential dosimetric benefits associated with the CyberKnife (CK) tumor tracking capability, wherein an extra margin for respiratory tumor motion is not required, when compared to respiratory-gated volumetric-modulated arc therapy (VMAT) for hepatocellular carcinoma (HCC).


Methods

Twenty-nine HCC patients previously treated with double-arc VMAT were enrolled. In each VMAT plan, the individual internal target volume (ITV) margin around the tumor was determined by measuring its motion over 30–70% of respiratory phases using four-dimensional computed tomography, followed by a 5-mm isotropic margin for the planning target volume (PTV). For each VMAT plan, two CK plans were generated using the original (CKoriginal, ITV included) and modified PTVs (CKmodified, ITV excluded) for comparison. In each case, the CKoriginal and CKmodified plans were compared to the original VMAT plan in terms of the dosimetric parameters including the conformity index (CI), PTV coverage (CO), organs at risk (OAR) doses, and normal liver tissue sparing.


Results

The original PTVs with median 24 cc (range, 9–65 cc) were significantly reduced to median 12 cc (range, 5–41 cc) in the CKmodified plans. Statistically significant differences in plan qualities were observed between the VMAT and the CK plans: mean CI, 1.05 in VMAT vs. 1.17 in both CK plans (p < 0.001); and mean CO, 93.0% in VMAT vs. 96.6% in CKoriginal and 96.9% in CKmodified (p < 0.001). The average volume of normal liver tissue receiving > 15 Gy was significantly decreased in the CKmodified plan, as compared to that in the VMAT and CKoriginal plans, by 1.75- and 1.61-fold, respectively.


Conclusions

The tumor tracking capability of the CK system can significantly decrease the volume of normal liver tissue receiving > 15 Gy, while maintaining high precision in target localization, conformity, tumor coverage, and dose sparing of the OAR. Therefore, it can be a valuable SBRT option, particularly for HCC patients with poor liver function.

more...
No comment yet.