Mass Screening for Early Detection of Breast Cancer Conducted in Miyagi Prefecture

Since 1977, mass screening for early detection of breast cancer has been conducted in Miyagi Prefecture, Japan. We have achieved a detection rate of approximately 0.1% by means of physical examination and cytologic studies of nipple discharge. Twenty-four cases (40%) of T0 cancer that had not been detected by physical examination were detected by cytologic examination alone. In 1989, to improve the detection rate of early breast cancer, a trial of mass screening combined with mammography was carried out in women aged over 50. Breast cancer was found in 35 subjects with a detection rate of 0.28% by screening mammography. In contrast, a rate of only 0.09% was obtained without mammography. A higher detection rate (73%) for early breast cancer was obtained in the group screened by mammography than in that (39%) without mammography. These results suggest that screening mammography with physical examination in women aged over 50 can reduce the number of cases of so-called interval cancer.