A Shot In The Arm For Cancer Patients?Kate Murphy
When Ernest Graf, retired president of Ben Kahn Furs in New York, was diagnosed with prostate cancer in 1993, he underwent radiation treatment. Then he opted to receive an experimental vaccine developed by Memorial Sloane-Kettering Cancer Center in New York. "I didn't want the side effects" associated with hormonal therapy, such as lethargy and diminished libido, says Graf, 79, who received four shots over 18 months. With his cancer now in remission, he credits his good health to the vaccine and to an active lifestyle that includes biking and skiing: "It strengthened my immune system without slowing me down," he says.
Graf is one of thousands of patients in the past decade who have received experimental vaccinations that prompt their immune systems to fight cancer. The vaccines are easy to administer and have few side effects beyond occasional flu-like symptoms and irritation at the site of the shots. While by no means a cure, they hold promise as a supplement to such standard anticancer weapons of surgery, radiation, and chemotherapy.
Already in use in Europe, the first cancer vaccines have yet to become widely available in this country. That may change next year, pending U.S. Food & Drug Administration approval of colon-cancer vaccine OncoVAX from Rockville (Md.)-based Intracel and melanoma vaccine Melacine from RibiImmunoChem Research of Hamilton, Mont. Clinical trials of at least two dozen others for ovarian, breast, lung, pancreatic, and prostate cancer are under way.
Scientists have been on the trail of a cancer vaccine since the 1800s, when they noticed that tumors sometimes shrank when patients contracted bacterial infections. Indeed, the first vaccines used bacteria that revved up the immune system. But they didn't work well because cancer is hard for the body to I.D. as an enemy. Basically, the bacterial vaccines signaled the immune system to fire without giving it a target. Only in the last decade have researchers set their sights more accurately.
Unlike vaccines for measles and polio, this bunch of experimental vaccines are intended to prevent the recurrence of cancer in patients who have had the standard treatments. Depending on the type of cancer and the patient's response, treatment may involve injections given over six weeks to two years. You can get a list of institutions conducting clinical trials on the vaccines from the National Cancer Institute (800 4-CANCER; cancernet.nci.nih.gov/pdq.htm).
Since the 1970s, researchers have latched on to three approaches to making the vaccines (table). Autologous vaccines use a person's own tumor cells, which are irradiated and combined with a bacterium or other agent that elicits an immune response. The body's violent reaction to the concoction, the thinking goes, creates a killer instinct toward new tumors. A study in British medical journal The Lancet in January said Intracel's autologous vaccine cut the colon-cancer recurrence rate by 50% over five years in patients in whom the disease had begun to spread beyond the tumor site. Since the vaccine has to be tailored to each person, Intracel plans to set up facilities around the country to ease delivery.
Several teams, meanwhile, are working on more generalized vaccines. Dr. Philip Livingston and colleagues at Sloane-Kettering have identified a molecule, GM2, that shows up on most melanoma cells. They make it in the lab and combine it with substances derived from mollusks and the bark of the South American soap bark tree. The brew, Livingston says, elicits "an immune response in virtually 100% of patients." A study with 600 subjects has been under way for 2 1/2 years to see if this response reduces recurrence.
The third approach is to use genetic material. Vaccines for pancreatic and prostate cancer developed in 1992 at Johns Hopkins University Medical School in Baltimore, and now in clinical trials, combine a gene for a "messenger protein," cytokine, with a patient's tumor cells. It's like pinning a note to the tumor cell that reads: "Kill me and anything that looks like me," says Dr. Drew Pardoll, professor of oncology at Hopkins. Not a bad ploy to add to the anticancer battle plan.