June 1, 2009 (Orlando) -- For the first time, a vaccine that trains the immune system to seek out and attack cancer cells has been shown to shrink tumors in people with melanoma.
There are even indications that people given the vaccine live longer, but patients need to be followed longer before researchers can be sure, says Patrick Hwu, MD, head of melanoma medical oncology at the University of Texas M.D. Anderson Cancer Center in Houston.
Hwu presented the results at the annual meeting of the American Society of Clinical Oncology.
Melanoma Vaccine: How It Works
Unlike the vaccine that helps prevent cervical cancer in healthy women, the melanoma vaccine is designed to help people who already have cancer.
The vaccine is given along with interleukin-2, or IL-2, the standard treatment for melanoma. IL-2 stimulates the immune system to attack and kill cancer cells. Tumors shrink in one in four patients with advanced melanoma who get this treatment.
The vaccine contains a substance, called gp100, that is on the surface of melanoma cells. The idea is that the immune system will see this as a threat and incite an even stronger attack against cancer cells.
“The vaccine is capable of taking immune system soldiers to boot camp. Then, interleukin-2 multiplies them into an army,” Hwu tells WebMD.
Melanoma is the deadliest form of skin cancer. This year in the U.S., there will be an estimated 68,720 new cases and 8,650 deaths from the disease, according to the American Cancer Society.
Melanoma Vaccine Shrinks Tumors
In the study, people with advanced melanoma were given the vaccine or a placebo injection, followed by four days of intravenous interleukin-2 treatment. This was repeated every three weeks until the tumor shrank or the cancer progressed.
Tumors shrank in 22% of patients given the vaccine plus interleukin-2, compared with 10% of those given interleukin-2 alone. The vaccine also extended the time until the cancer started growing, from about one-and-a-half months for interleukin-2 alone to nearly three months for the one-two punch.
That may not sound like much, but cancer advances are made in baby steps, says Len Lichtenfeld, MD, deputy medical director of the American Cancer Society.
Lichtenfeld tells WebMD that there’s reason for “cautious optimism.” A lot of cancer vaccines that seemed promising in early studies haven’t panned out, he says.
Louis M. Weiner, MD, head of the Lombardi Comprehensive Cancer Center in Washington, D.C., says the vaccine study is the latest in a series showing that the immune system can be mobilized to attack cancer.
“Many of us believe that a combined approach that includes an immune system attack on cancer cells will ultimately prove to be most useful in controlling cancers such as melanoma,” he tells WebMD.
Hwu says the next step is to try to reproduce the findings in a longer, larger study. Also, his team hopes to add yet another punch -- in the form of an agent that takes the brakes off the immune system.
Then, the immune system soldiers can proliferate with impunity, hopefully killing even more cancer cells, he explains.