Thoughtful review of a cancer-preventing drug that doctors don’t use—probably for good reasons.
Finasteride (sold by Merck as Proscar) blocks conversion of testosterone into the even stronger dihydrotestosterone. Blocking this conversion shrinks the prostate gland, which swells as men age, often obstructing the urinary passage. In 1992 the FDA approved finasteride to treat benign prostatic hyperplasia. Researchers immediately wanted to learn if a drug that repressed normal prostate cells might do the same to malignant cells. In 1993, nearly 19,000 volunteers aged 55 and older began a study in which half took finasteride and half didn’t. After ten years, the men taking finasteride were shown to have a 25 percent lower chance of developing prostate cancer. That was the good news. The bad news was that among the smaller number who did get cancer while taking finasteride, a higher percentage developed more aggressive, less curable cancers. Given a drug that prevents cancer in many patients but might harm a few, doctors have made a choice: They don’t prescribe it. Since finasteride may save lives, some authorities accuse doctors of focusing too much on individual patients to the detriment of society. Justman (English/Univ. of Montana) maintains that this is the right choice. He recounts cautionary tales of occasions when physicians or other experts decided individuals must suffer for the greater good; his evidence includes the Tuskegee study, in which African-American sharecroppers were denied treatment for syphilis. He agrees with general medical opinion that it’s wrong to conclude, if the number of cancers prevented by finasteride exceeds the number induced, that the drug has a “net benefit.” A unique glory of scientific medicine is a vivid awareness of our ignorance, Justman writes. Until doctors understand what causes prostate cancer and how finasteride works to prevent it, they prefer to observe a guiding principle of the Hippocratic Oath: “First, do no harm.”
An eloquent account of the medical profession’s sometimes cautious approach to advancement.