Guidelines for screening for breast cancer. Is a revision in order?

Screening women over the age of 50 for breast cancer has clearly been proven to be capable of reducing population mortality from breast cancer. Population based screening for women aged 40 to 49 has not been shown to be effective, and in several trials there is an early excess breast cancer mortality in the screened population. Because tumors tend to grow more rapidly in younger women than in older women, those trials performed at biannual intervals will detect only the intermediate and slower growing lesions. The more rapidly growing tumors will occur between screens. Furthermore, maintaining a high positive predictive value will lead to a lower sensitivity rate. If the screening interval is too long or the positive predictive value too high, the reassuring effect of a false-negative screening examination may contribute to delay in diagnosis beyond even the usual clinical detection threshold. This may cause more deaths in the study population than in the control population. Guidelines that take the various factors into account have been proposed.