The drug vemurafenib targets melanomas with BRAF mutations, but treatment usually stops working after just 6 to 8 months because tumors become drug-resistant. However, resistance could be avoided by giving people periodic breaks from treatment, suggests work presented at the 2013 meeting of the American Association for Cancer Research. The researchers found that stopping treatment slowed tumor growth in 14 out of 19 people with vemurafenib-resistant melanomas. They also found that intermittent treatment (4 weeks on and 2 weeks off) prevented vemurafenib resistance in human melanomas implanted in mice. This strengthens the researchers' previous work showing that vemurafenib-resistant melanomas actually depend on the drug to grow.