Abstract
A cohort study to compare mass screening with and without mammography was conducted in Miyagi Prefecture, Japan in order to establish whether the effectiveness of breast cancer screening would be improved when mammography was combined with physical examination. A trial of mass screening combined with mammography was carried out in 9634 women aged over 50. Lateral imaging of the breast using single-view film mammography was performed at the first stage of mass screening in addition to physical examination of the breast. Results in the trial were compared with those obtained in 35511 age-matched subjects without mammography. Thirty breast cancers were found in the trial with a detection rate of 0.31%, which was much higher than that (0.08%) obtained by physical examination without mammography. In 15 of the 30 patients the breast tumor was not palpated at the first screening, but abnormal findings were detected in the mammography. A higher rate (73%) of early breast cancer was obtained in the screening trial with mammography than that (39%) obtained in the screening with physical examination alone. Mass screening combined with mammography is superior to that without mammography for breast cancer screening, especially for the detection of non-palpable, early breast cancer.