Preliminary results of the trials were presented at the European Cancer Conference in Hamburg, Germany, in September.

Lesions reversed for 75 percent

Thomas Mang, clinical associate professor of oral and maxillofacial surgery, along with colleagues in radiation oncology and dermatology, treated eight subjects with a total of 86 chest-wall lesions and nine subjects with a total of 121 Kaposi's sarcoma lesions, a common complication of AIDS. All patients received one PDT treatment in the Photodynamic Therapy Center in The Buffalo General Hospital.

Results showed that:

- Seventy-five percent of the Kaposi's sarcoma lesions were reversed completely and another 19 percent showed partial reversal.

- Ninety-two percent of the chest-wall lesions were completely reversed and the remaining 8 percent showed partial reversal.

- The only adverse reactions experienced by subjects were due to sun exposure while the photoreactive agent used in the therapy was still active.

Photodynamic therapy is based on the propensity of certain light-sensitive drugs to accumulate, or localize, in cancer cells. This selective retention allows researchers to direct a beam of light into the tumor or lesion, which activates the drug, tin ethyl etiopurpurin (SnET2). The resulting reaction kills the cancer cells.

Mang, who has done extensive research with PDT, said these results support earlier findings indicating that photodynamic therapy holds great promise for treating cancerous lesions of the skin.

Cosmetic results good

"Compared to other treatments for Kaposi's sarcomas, PDT is easier on the patient, you can treat large numbers of lesions at one time and the cosmetic results are very good," he said. "PDT also doesn't interfere with HIV status and any other treatment patients may be receiving."

Results with recurrent breast cancer of the chest wall were equally exciting, he said. "These lesions, if left untreated, are annoying, painful and they can grow. Treating them with more radiation and chemotherapy after patients already have undergone these treatments following mastectomy is futile and makes patients sick.

Treatment localized

"PDT is a very localized treatment, does not interfere with chemotherapy and there are none of the usual side effects of cancer therapy," he said. "Many lesions can be treated in one session, and the therapy is repeatable if the response isn't complete."

Mang said PDT appears to be most effective on small tumors that are discovered early. Because the light-sensitive drug is absorbed by all body cells, albeit to a lesser degree than cancer cells, patients need to protect themselves from the sun for two weeks following treatment until the drug becomes inactive.

Additional researchers in the

trials were Ronald Allison and Vitune Vongtama of the Department of Radiation Oncology, and B. Dale Wilson of the Department of Dermatology. All also are affiliated with the Photodynamic Therapy Center at The Buffalo General Hospital.