In 1975, breast cancer mortality among women 30-79 years of age was 48.3 deaths per 100,000 women. This rate increased slightly to 49.7 per 100,000 in 1990, then fell to 38.0 per 100,000 in 2000 (a 24% drop since 1990). Dana-Farber investigators and six other research groups developed independent statistical models to assess the relative and absolute contributions of screening mammography and treatment to the reduction in breast cancer mortality.
The proportion of the total reduction in the breast cancer mortality rate attributed to screening varied from 28% to 65% in seven groups, with a median of 46%. For adjuvant treatment, this proportion ranged 35% to 72% with a median of 54%. Although there was some variation in actual estimates, all seven models concluded that both screening mammography and treatment have contributed in reducing the breast cancer morality rate in the United States.