Chicago ? Researchers have scored the first big win against melanoma, the deadliest form of skin cancer. An experimental drug significantly improved survival in a major study of people with very advanced disease.

The results, reported Saturday at a cancer conference, left doctors elated.

“We have not had any therapy that has prolonged survival” until now, said Dr. Lynn Schuchter of the Abramson Cancer Center at the University of Pennsylvania, a skin cancer specialist with no role in the study or ties to the drug’s maker.

The drug, ipilimumab (ip-ee-LIM-uh-mab), works by helping the immune system fight tumors. The federal Food and Drug Administration has pledged a quick review, and doctors think the drug could be available by the end of this year.

“People are going to have a lot of hope and want this drug, and it’s not on their doctors’ shelves,” although some may be able to get it through special programs directly from its maker, Bristol-Myers Squibb Co., Schuchter said.

Melanoma is the most serious form of skin cancer. Last year in the United States, there were about 68,720 new cases and 8,650 deaths from the disease. Worldwide, more than 50,000 people die of melanoma each year.

“The incidence is rising faster than any other cancer,” said one of the study’s leaders, Dr. Stephen Hodi of Dana-Farber Cancer Institute in Boston. “When it spreads to vital organs, it’s almost always fatal.”