Promotion of quality-controlled mammography alone as a screening modality in Japan

The rate of breast cancer screening in Japan has not increased, and it is thought that one of the reasons is the principle that mammography (MMG) and clinical breast examination (CBE) be carried out in combination. Nationwide, there is a shortage of physicians qualified to perform CBE, and in some regions mass-screening is performed by MMG alone out of a mobile MMG bus. In Shikoku, MMG is performed alone as a screening examination in Kochi and Ehime Prefectures.

A comparative analysis of the data generated by MMG alone in breast cancer screening in the four prefectures of Shikoku during the 2005-2009 period was performed.

The overall attendance rates, recall, cancer detection, early-stage cancer detection, and the positive predictive value (PPV) were 16.8-24.5, 6.0-12.8, 0.26-0.37, 63.1-79.7, and 2.8-4.3 %, respectively. Almost no differences were seen between the results for MMG alone and combined MMG/CBE screening. In addition, the cancer detection rates based on the Japan Cancer Society's nationwide data were 0.25 % with combined MMG/CBE screening and 0.21 % with MMG alone, showing almost no difference.

No differences were seen between the results (i.e., recall rate, cancer detection rate, early-stage cancer detection rate, PPV) for MMG alone and MMG/CBE screening in the four prefectures of Shikoku compared with the Japan Cancer Society's nationwide data. In order to improve the mammographic screening rate in Japan, quality-controlled mammography as a stand-alone examination should be promoted, and performed biennially for women aged 50-74 years.