Previously, no more than 10 percent of patients responded to any of the other available treatments, the researchers said.
The main limitation with Zelboraf is that tumors eventually become resistant.
Side effects include joint and muscle aches, which are fairly easy to manage in most patients, Sosman said.
Some patients also experienced skin changes, including sun sensitivity and rashes. "Patients develop incredible photosensitivity so patients have to be very careful about direct sunlight and use sunscreen as well as just staying out of the bright sun," Sosman said.
Also, the drug indirectly causes squamous cell cancers of the skin in some patients. "These generally never spread and are easy to remove, and patients who have gotten them can remain on treatment," Sosman said.
The drug costs around $10,000 a month, Sosman noted. "It's comparable to other cancer drugs that have shown improvement in survival, but like a lot of cancer drugs, it's expensive," he said. "You probably need to take the drug for an indefinite period of time."
Drug maker Hoffmann-La Roche funded the study.
About 70,000 Americans are diagnosed with melanoma each year. Of these, about 8,000 will die from the disease.
Dr. Michele Green, a dermatologist at Lenox Hill Hospital in New York City, said the study is a leap forward. "This finding is significant in that there is nothing right now for this kind of cancer. It's basically a death sentence," she said.
That the researchers showed improved survival is clinically significant, she said, even though "the survival wasn't that much longer."
If the drug were given for early-stage melanoma, it's possible it would improve survival even more, Green said. Eventually, she said the research will lead to a cure for melanoma.
"There's new hope every single day for melanoma," she said. "I think in our lifetime we are going to see cures for this cancer."
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