WHAT if there was growing evidence that an already-existing drug, taken daily, might dramatically reduce the risk of breast cancer? Shouldn't that be more newsworthy than fund-raising walkathons done in the quixotic pursuit of a simple cure? More noteworthy than the latest lab test which classifies an environmental chemical as a rodent carcinogen? U.S. scientists, led by Harvard's Dr. Peter Goss, this week began recruiting women at high risk of breast cancer to participate in a study of what may well be just such a drug. That "chemical prevention" of cancer has come so far will be a shock to...