The statistical evaluation of the female breast cancer detected by mass screening in Hokkaido

Abstract In Hokkaido, 113, 612 women were subjected to mass screening of breast cancer from 1973 to 1983. Out of them, 74, 285 (56.3%) were examined once and the remainder twice or more: 4,798 (4.2%) were advised to receive further precise examinations and 99.8% of them underwent the second examination. Breast cancer was detected in 377, in which 291 (77.2%) were detected by the first examination and 33 (3.8%) were so-called "interval cancer" with the mean interval of 19.3 months. The detection rate was 0.3%. Histologically non-invasive cancer was seen in 26 (6.9% of 377). Despite a recent significant increase in detection rate of the earlier stage of breast cancer, the present study showed no evidence of a decrease in advanced cancer. The prognosis of the patients who had curable operation revealed 86.9% in 5 year survival rate and 40% in 10 year survival rate.