ORLANDO, Fla., May 31, 2009— -- In what researchers are calling a first, a vaccine that targets skin cancer cells shrinks tumors and cuts the chance that the disease will return.
In a large clinical trial, more than twice as many people who got the vaccine saw their tumors shrink compared to those who didn't get the drug, Dr. Douglas Schwartzentruber of Indiana University told colleagues at the annual meeting of the American Society of Clinical Oncology.
The study is "one of the first to show positive, promising results for a cancer vaccine" to fight the often-deadly skin cancer melanoma, Schwartzentruber said.
When it spreads from its original site, melanoma is difficult to treat and resistant to most therapies, he said. "These results will give patients and the oncology community hope that we are making some progress against this disease," Schwartzentruber said.
The vaccine consists of a molecule -- dubbed gp100 -- that is on the surface of melanoma cells. The idea is that the immune system will attack not only the molecule itself, but also the cancer cells that display it.
In previous trials, Schwartzentruber said, the vaccine has had little effect.
But in a new wrinkle, this time it was given with interleukin-2, a signalling molecule known to stimulate the immune system. In some studies, one in four patients treated with the interleukin-2 alone has had measurable tumor shrinkage, Schwartzentruber said.
The study, which is continuing, enrolled 185 patients with melanoma that had spread to other sites, such as the lungs. Half were treated with interleukin-2 alone and half were given the vaccine as well.
Among those who got both drugs, 22 percent saw their tumors shrink, Schwartzentruber said, compared to 9.7 percent of those who got interleukin-2 alone.
The vaccine also added about a month and half to the period before the cancer shook off the effects of the drug and began to spread again.
The differences may seem small, Schwartzentruber said, but in many cancer treatments, progress is measured in small steps that eventually add up.
Skin Cancer Vaccine Study a 'First Step'
Schwartzentruber said this combination is only a first step. Other combinations of drugs that stimulate the immune system and target cancer cells need to be developed and tested in order to improve the results, he said.