Effectiveness of mass screening for breast cancer in Japan

Background: Breast cancer screening has been conducted in Japan mainly by physical examination, the standard method for breast cancer screening according to the Law of Health Services for the Elderly. The purpose of this study was to evaluate the effectiveness of mass screening for breast cancer in Japan. Methods: We calculated the average coverage-rates for breast cancer screening per year from 1986 to 1995 for women aged 30-69 years for all of the 3255 municipalities in Japan, selecting "high coverage-rate" municipalities with average coverage-rates of 20%, 30%, 40% or more. Two municipalities were selected as "controls" for each high coverage-rate municipality, and were matched for population, National Health Insurance rate, and the age-adjusted death rate from cancer of the female breast in the period 1986-90. We compared the change in the age-adjusted death rate from 1986-90 to 1991-95 of the high coverage-rate municipalities and the comparable controls. Results: The percent reduction in the age-adjusted death rate from cancer of the breast in the high coverage-rate municipalities was statistically significantly greater than those in the controls. Conclusions: The results suggest that mass screening for female breast cancer, mainly by physical examination, contributed to the reduction of mortality from breast cancer.