[Cancer screening in Japan--a critique from the epidemiological viewpoint]

The present status of cancer screening in Japan has been critically reviewed from an epidemiological point of view. Cancer screening programs for stomach cancer and uterine cervical cancer were introduced in the 1960s on the basis of the naive belief of many clinicians that early diagnosis is beneficial: Many studies now show that this belief unfounded. Therefore, before the introduction of screening programs as a general policy, epidemiological evaluation is essential. The general principles involved in evaluation of cancer screening were discussed. In contrast to stomach cancer and uterine cervical cancer, cancers of the lung, breast and colorectum are increasing in Japan. In the case of lung cancer, primary prevention, i.e., smoking control, should be preferred, because lung cancer screening has not yet been shown to be effective. In the case of breast cancer and colorectal cancer, screening trials should be designed and appropriate evaluations should be conducted before their implementation as cancer control measures.