Current controversies in screening: cholesterol, breast cancer, and prostate cancer.
Physicians must make decisions in day-to-day practice even when the balance of benefit and harm is not yet known. Adopting a clinical policy about screening is a case in point. Three controversies in screening healthy adults illustrate different aspects of resolving a dispute when the evidence is incomplete. The major controversy in cholesterol screening is whether to screen young adults. There has never been a randomized trial of treatment, let alone a trial of screening, in young adults. However, a patchwork of evidence strongly suggests that, because the baseline risk of coronary heart disease (CHD) is very small in young adults, the absolute reduction in risk from treatment would be very small. In breast cancer screening, randomized trials do not show conclusively that periodic mammography for women aged 40-49 years reduces breast cancer mortality. A 7-10 year delay between the first mammogram and a reduction in deaths from breast cancer suggests the hypothesis that the only benefit of screening women aged 40-49 years occurs from mammograms performed after age 50. There is no high quality evidence that early detection and treatment reduce the death rate from prostate cancer. In lieu of randomized trial data, we must depend on a decision analysis that shows that screening middle-aged men is cost-effective relative to other preventive services. However, this result depends on using optimistic survival data in the decision model, and most organizations do not recommend routine screening. The best strategy is to discuss the harms and benefits, and let the patient decide.