Zelboraf, a drug used to treat advanced cases of the deadly skin cancer melanoma, nearly doubles the length of patients' lives, a new study has found.

The drug was approved last year by the Food and Drug Administration to treat patients with malignant melanoma whose tumors carry a specific gene mutation, called BRAF V600E. Almost 50 percent of people with melanoma have the mutation.

At the time of the drug's approval, it was clear that patients taking the drug lived longer than those not taking it, but exactly how much longer could not be measured from earlier data.

In the new study, researchers looked at 132 melanoma patients with the mutation, mostly men under age 65.

Patients who took Zelboraf for a little over a year survived 15.9 months, on average, whereas advanced melanoma patients given other treatments typically live about eight months. The researchers found that 77 percent of these patients survived at least six months, 58 percent survived at least one year and an estimated 43 percent survived at least 18 months.

About half the patients in the study saw their cancers respond to the drug, and that response lasted for only about seven months.

"Advanced melanoma is a fatal disease," said Dr. Kim Margolin, a medical oncologist at the University of Washington who was not involved in the study. "Rarely can these patients be cured."

Though the drug isn't a cure, "people live longer than they would have," Margolin said.

The findings are published today (Feb. 22) in the New England Journal of Medicine.

In a study published last year, researchers compared the survival rates of 675 malignant melanoma patients who took Zelboraf with patients who took dacarbazine, a chemotherapy drug.

At six months, they found that 84 percent of patients who took Zelboraf were still alive, compared with 64 percent of those taking dacarbazine.

Study participants taking Zelboraf experienced side effects, including joint pain, rash, fatigue and a non-threatening form of skin cancer. Nearly half had to have their doses reduced, and 85 people had to get their dose interrupted.

 But with cancer drugs, that's generally common, according to Margolin.

"It's common to reduce doses of drugs to improve or make side effects more tolerable," she said.

The drug company Hoffmann-La Roche, which makes Zelboraf, funded the study.

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