THURSDAY, Sept. 19, 2002 (HealthDayNews) -- Researchers are using an inventive strategy that includes a deliberate weakening of the body's immune defenses to mount a last-ditch attack against melanoma, the deadly skin cancer.
"It does seem counterintuitive," because the more conventional approach would be to foster a more intensive attack by the immune system against cancer cells, says Dr. Steven A. Rosenberg, chief of surgery at the National Cancer Institute (NCI) and leader of the research team.
But in this case, the weakening is done to increase the aggressiveness of the attack by killer immune cells, grown in the laboratory and transferred back into the patients' bodies. The approach has had some success in patients with advanced melanoma who had not responded to conventional treatments, says a report in the current issue of Science.
"Every one of them had been treated with surgery, chemotherapy and other treatments," says Rosenberg. "These are patients at the end stage of the disease with limited life expectancy."
The idea of taking killer T cells from the body, multiplying them in culture dishes and transferring the expanded population back into the patient has been around for a while. Past efforts have not been successful, however, because the transferred cells tended to disappear quickly, partly because suppressor cells kept them from multiplying.
What the NCI researchers added to the strategy was a round of chemotherapy that suppressed the immune system's tendency to reject new cells just before the laboratory-grown T cell transfer was made.
Four of the 13 patients given the treatment had mixed responses, in which some melanoma tumors shrank and others did not. In six others, a number of tumors throughout the body shrank, with the response lasting from two to 21 months. No effect was seen in three patients.
The most encouraging results were seen in two patients. In one, more than 95 percent of the melanoma tumors shrank, with the response continuing for eight months. In the other, 99 percent of the tumors had disappeared seven months after the treatment began.
The weakening of the immune system did lead to some mild autoimmune disorders, including occasional infections, the skin disease vitiligo, and, in one patient, uveitis, inflammation of the iris of the eye that was successfully treated with steroid drops. Such side effects are "a small price for getting rid of your cancer," Rosenberg says. The patients' immune system function recovered over a period of months.
This is "a highly experimental study that is being done only at the National Cancer Institute," Rosenberg says. The study will be expanded, he adds: "We already have made some improvements in the treatment, and hopefully in the next six months we will expand it to other patients with cancer."
Target tumors in the upcoming study will include cancer of the breast, ovary and prostate, Rosenberg says. In theory, at least, the strategy could also be used against AIDS. "We can raise T cells against viral agents such as HIV, so the potential exists," he says. Such studies would have to be done elsewhere, he says.
The technique is expensive, as are most experimental treatments, Rosenberg acknowledges. But "I think it can be made practical," he says.
What To Do
Information about melanoma is available from the National Cancer Institute or the American Cancer Society.
