The study, published in the New England Journal of Medicine, says therapeutic cancer vaccines -- unlike vaccines that prevent infection, are intended to jump-start the immune system to help it battle existing tumors.
"This is the first time that a vaccine has shown benefit in the treatment of patients with metastatic melanoma. The trial is an early example of success with a cancer vaccine," Dr. Howard Kaufman, a study co-investigator who is director for the Rush University Cancer Center, says in a statement.
"If we can use the body's own defense system to attack tumor cells, we provide a mechanism for ridding the body of cancer without destroying healthy tissue."
The researchers randomly assigned 185 patients with metastatic melanoma -- the most serious type of melanoma -- to either a combination of the peptide vaccine, which is a small portion of protein that is present on the surface of the melanoma cancer cells, and Interleukin-2, a drug that activates the immune system, or a high dose of Interleukin-2 alone.
The study, published in the New England Journal of Medicine, found about 16 percent of study participants given the vaccine and Interleukin-2 combination saw tumors shrink by 50 percent or more, compared with 6 percent given Interleukin-2 alone.