[Characteristics of screening-detected breast cancer and trends in its therapy].

: Recently breast cancer has become one of the most common malignancies and one of the major causes of cancer death in Japan. In order to detect earlier stage breast cancer and to stop the increasing mortality, there is a greater need for mass screening. Mass screening performed by physical examination has a history of about thirty years in Japan, but it has had no effect in reducing breast cancer mortality. A new modality, mammography, is effective to detect non-palpable lesions, so it is expected to improve the accuracy of screening and reduce the mortality of breast cancer. Randomized trials in western countries have demonstrated that screening with mammography is effective for breast cancers in women aged 50 -69. In Japan, limited studies reported that effectiveness of screening was improved when mammography was combined with physical examination for detecting early breast cancer, but it is still unknown whether screening reduces breast cancer mortality. Since indications of breast conservation therapy have been rapidly extended it follows that breast conservation surgery for screening-detected cancer has increased. In Japan, because of its medical system, it seems impossible to conduct randomized trials for evaluating the efficacy of screening. Thus, it is important to interpret the screening data in western countries and to compare data with those from screening trials of Japan in the future.