BREAST-CANCER SCREENING

Radiographic imaging of the breast began in the early-years of the twe ntieth century. Continuous advances in film quality, energy sources, t argets, grids, and filters have all contributed to superior image reso lution. Federal quality standards now regulate screening mammography, and mass screening for breast cancer has become widely accepted in the United States. Wider application of screening has resulted in a drama tic apparent increase in incidence rates of breast cancer; a large pro portion of this increase is in ductal carcinoma in situ. During the pa st 30 years, nine prospective, randomized trials to evaluate the abili ty of screening mammography to reduce mortality from breast cancer hav e been completed. These trials show a 30% reduction in mortality for w omen ages 50-69 years, but the benefit to women aged 40-49 years remai ns uncertain. This uncertainty is largely attributable to the lack of properly designed and conducted studies to evaluate screening efficacy in younger women. Although there is no biological reason to predict p oor screening performance in the younger age groups, the sensitivity o f screening mammography is lower in younger women. Additional data sug gest that screening intervals longer than 12 months are ineffective in women younger than 50 years. With shorter screening intervals, the co st associated with screening mammography is comparable to other life-s aving measures widely applied in the population. New breast imaging te chniques hold promise for superior image quality, but they remain inve stigational as tools for mass screening. Until primary prevention of b reast cancer is a reality, mass screening remains available to reduce mortality from breast cancer.