Among developments reported at the meeting of the American Society of Clinical Oncology:

- The Genentech drug Herceptin is the first proven cancer medicine that works by attacking the genetic defects that cause the disease. Given to women with advanced breast center, it increases survival an averagre of three months. Experts hope for more dramatic effects when it's given in earlier stages of the disease.- Raloxifene, a medicine developed for the brittle-bone disease osteoporosis, appears to cut older women's risk of breast cancer by about two-thirds without raising the hazard of uterine cancer.

- An eight-year follow-up study in Quebec found that the PSA test, a standard part of older men's checkups, sharply reduces the risk of dying from prostate cancer by finding the disease in treatable early stages. Skeptics caution this does not settle the controversy of whether testing and early detection actually translates into longer life for men already in their later years.

- A vitamin A derivative called 13-cis-retinoic acid is effective in the childhood nervous system cancer called neuroblastoma, which strikes 500 people in the United State each year. Survival after three years was 55 percent in the vitamin patients, compared with 13 percent among those getting standard chemotherapy.

- Taxol, a standard drug for advanced breast cancer, also works if given in early stages of the disease. A large study of women whose cancer had spread only to the lymph nodes found taxol increased survival after two years by 2 percentage points, to 97 percent.