The results from an abstract, or brief summary, of the study showed that Zelboraf led to a median overall survival of 13.2 months compared with 9.6 months for those who received dacarbazine chemotherapy. That translates into a 38 percent reduction in the risk of death from the disease, researchers said.

The overall survival data, which will be presented at next month's American Society of Clinical Oncology meeting in Chicago, is a follow-up to a pivotal 675-patient Phase III study that was presented at the meeting last year and led to the drug's approval.

The study was halted early based on clear evidence of the Roche drug's efficacy so that patients in the chemotherapy arm of the trial could be given Zelboraf, known chemically as vemurafenib.

The new analysis includes 81 of the patients originally in the chemotherapy arm of the study who crossed over to receive Zelboraf, the company said.

Zelboraf, an oral drug, is a targeted therapy designed for patients that have a mutation of a gene known as BRAF. About half of all patients with melanomas - the deadliest form of skin cancer - have the BRAF mutation.

The drug has been hailed as a prime example of personalized medicine, or targeting a drug for patients deemed most likely to benefit based on their genetic makeup.

"The life expectancy for these patients isn't very long, so they have an opportunity to have therapy that on average improves survival by a really significant amount, and then of course there are also people who do (even) better," said Jennifer Low, group medical director in product development for Roche's Genentech unit.

Roche is also testing Zelboraf in other tumor types, and in combinations with other experimental medicines it is developing as well as with drugs designed to use a patient's immune system to fight cancer, known as immunotherapies.

(Reporting By Bill Berkrot in New York; editing by Matthew Lewis)

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