Mass screening for breast cancer: comparison of the clinical stages and prognosis of breast cancer detected by mass screening and in out-patient clinics.

To establish the criteria for assessing the life-prolonging effect of mass screening for breast cancer, clinical stage and prognosis of breast cancer detected by mass screening in 11 regions of Japan were compared with those for matched patients in out-patient clinics. A total of 728 patients detected by mass screening and 1,450 found in the out-patient clinics were reviewed. The stage of the disease was Tis or I in 40.9% of the patients detected by mass screening, and 28.7% of those found in the out-patient clinics. In contrast, stage III was found in 9.3% and 14.6%, respectively, indicating that early stages were significantly more common in the patients detected by mass screening. The overall survival curve for the patients detected by mass screening was compared with that for those found in the out-patient clinics. The 5-year survival rate was significantly higher in the patients detected by mass screening (91.7% vs. 85.6%; P less than 0.01), while the 10-year survival rate was slightly higher in the same group of patients, but the difference from the other group was not significant (80.5% vs. 78.1%). Women who had conducted breast self-examination (BSE) showed a higher survival rate than those who had not conducted BSE.