Current Status of Screening for Breast Cancer and Tasks for Introduction of Mammographic Screening in Japan

In the United States and Europe the high mortality of breast cancer has been significantly reduced by mammographic screening of women aged over 50 years, theeffectiveness of which has been documented in many reports. In contrast, the effectiveness of such screening in women aged from 40 to 49 remains controversial.In Japan, breast cancer screening has consisted of physical examination alone, with inspection and palpation. Thus, more than half of the patients with breast cancer detected by this screening system are already aware of their lumps, the detection rate has been a little less than 0.1%, and the proportion of early-stage disease among breast cancers is only about 50%. It is difficult to detect breast cancer consisting of non-palpable tumors by physical examination, and the lowsensitivity of this screening method has been pointed out. In Japan, there is no difference in overall survival between cases detected by screening and those detected in outpatient clinics. The results of the mammographic screening trial performed in Miyagi and Tokushima, which were promising in terms of proportions of early-stage cancer and no nodal involvement, strongly suggest its usefulness in Japan as well as in other countries. However, long-term results are not yet available. It is advocated that screening for breast cancer should be performed by means of mammography to improve the screening sensitivity, and increase the proportion of early-stage breast cancers. Mammo-graphic screening, either mammography and physical examination separately or simultanously in combination, has been effective for women aged over 50 years in Japan. However, with regard to those aged under 49 years, further studies are needed.