EVALUATION OF MASS SCREENING FOR BREAST CANCER

Abstract

Mass screening for the simultaneous detection of both breast and thyroid cancer was conducted in Gunma Prefecture from April 1980 to March 1991. The total number of subjects was 314, 120 at the first screening by physical examination alone. There were 27, 329 women (8.7% of all subjects) who were referred for a second examination. The rate of attendance at the second examination was 95.8%. Breast cancer was detected in 240 women (detection rate ; 0.08%) and thyroid cancer in 288 (0.09%). The detection rate of breast cancer was approximately twice as high at the initial screening (0.11%) as at the subsequent periodic screening (0.06%), and higher in examinees aged 40 years or more. The coverage rate for examinees in the population aged 30 years or more was 14.6% in 1990. As the number of women screened increased from year to year, the repeat examinees occupied a greater percentage than those undergoing initial examination. Patients with breast cancer detected by mass screening showed an earlier stage and more favorable prognosis as compared with those of our outpatients. The 10-year survival rate was 90.4% in patients detected by mass screening and 72.3% in outpatients, a statistically significant difference (P<0.01). This screening program is effective for detecting breast cancer in an early and more curable stage and for reducing the mortality rate from breast cancer. In order to conduct the mass screening system with high quality and effective management, it is important to train physicians in screening techniques, and to educate women in the practice of breast self-examination. Furthermore, mammography in addition to a physical examination is necessary for the first screening.