Mass screening for control of breast cancer.

The serious import of breast cancer lies in its potential for metastatic spread, which probably starts early in the course of the disease. Detection of the lesion when immunocompetence can control the metastases leads to long-term survival. This usually involves detection of unsuspected, preclinical disease. This is the important lesson learned from the large screening program of the Health Insurance Plan of New York, where they used palpation and mammography. The substantial reduction in mortality over a matched control group has continued in a 15-year follow-up. Improved mammography techniques at the Guttman Institute, a mass screening project in New York, New York, conducted in cooperation with the American Cancer Society and in the Breast Cancer Detection Demonstration Project, which used the Guttman Institute program as a prototype, have led to substantially improved yield from mammography in screening. Three important factors in mass screening are discussed: (1) benefits versus hazards in mammography, (2) correct age to start screening, and (3) costs of screening.