Monday, January 20, 2003
Preliminary studies show Canvaxin can stem the recurrence of skin cancer.
By SHARI ROAN
LOS ANGELES TIMES
No one can question Dr. Donald Morton's tenacity. For 42 years, the medical director of the John Wayne Cancer Institute in Santa Monica, Calif., has been working on a vaccine to prevent a relapse of malignant melanoma, the most deadly form of skin cancer.
He began developing his vaccine, Canvaxin, in the early 1960s. Then working at the National Cancer Institute, he saw a patient whose cancer "just went away," even though it had spread to her liver and lungs. Such remissions, which tend to occur after the patient develops a bacterial infection, happen in about 1 in 2,000 to 5,000 patients with melanoma that has spread.
"We think the reason this happens is the immune system has been activated" by something like an unrelated infection, he said. "I said, if it happens spontaneously, maybe we can make it happen at will."
Based on his most recent study, Dr. Morton says his vaccine may cure about one-third more people with melanoma that has spread than existing therapies.
Advanced melanoma is usually treated with surgery to remove the tumor, followed by chemotherapy to kill cancer cells that may have escaped to distant parts of the body. Chemotherapy is toxic and, in such cases, often unsuccessful; the vaccine is intended as a replacement.
With the largest collection of melanoma cancer-cell lines in the world, Dr. Morton was able to identify three lines rich with specific antigens, substances that produce a strong immune response. The cells were treated with radiation so that, although still alive, they could not divide and cause more cancer.
Because the vaccine has so many target antigens, it is considered a "generic" vaccine that could be given to any melanoma patient, regardless of the person's particular type of tumor. Other researchers around the world also are working on "therapeutic melanoma vaccines," Dr. Morton said.
In a paper published in October, 49 percent of 935 patients who received the Canvaxin vaccine were alive after five years compared with 37 percent of 1,667 patients who received standard chemotherapy. Side effects include small sores on the skin (a reaction to the vaccine) that take about a month or two to heal, and temporary flulike symptoms.
The success of the most recent study, published in the October issue of the Annals of Surgery, prompted the National Cancer Institute to issue a $29 million grant for a phase-three, randomized, controlled trial at 55 centers around the world.
"One of the Food and Drug Administration's concerns is that, because of John Wayne Cancer Institute's expertise in treating melanoma, our results won't be duplicated at less specialized centers," Dr. Morton said.