Screening for breast cancer.

Randomised trials of screening have clearly demonstrated a substantial reduction of the order of 40% in breast cancer mortality among women aged over 50 years when regularly screened every two to three years by mammography. No other screening modality has been demonstrated to be of benefit, nor has screening of younger women. The major problem of breast screening at present is the need for greater understanding of the heterogenous natural history of the disease. The extent to which earlier diagnosis improves prognosis is poorly understood, but crucial to determining the full potential of screening.