Abstract
The purpose of cancer screening is to reduce cancer mortality. While mammography is the only method of breast cancer screening for which there is established evidence of a reduction in mortality, low sensitivity of the technique in dense breasts is a serious issue to be resolved. Although ultrasonography is a useful candidate for overcoming this problem, the recent trend toward introducing ultrasonography for population-based screening is still too early. Ultrasonography may offer higher sensitivity because it can detect breast cancer at an early stage based on mass shape, even in the dense parenchyma of premenopausal women. However, there is no manual on a standardized method of examination, no diagnostic criteria, and no evidence that ultrasonography screening reduces mortality. The Japan Strategic Anticancer Randomized Trial (J-START) was the first large-scale RCT to verify the quality and effectiveness of ultrasonography for breast cancer screening in women aged 40-49 years. The primary endpoints of this trial were inter-group comparisons of sensitivity and specificity, and the secondary endpoint was the inter-group comparison of the accumulated incidence rate of advanced breast cancer during the follow-up period. The primary and secondary endpoints are expected to be published at the end of 2014. Endorsement of the new modality is expected to increase the detection rate; however, it might also increase the recall rate, which would be an adverse effect of screening. It is necessary to make ultrasonography screening available, but it should not be introduced too hastily until evidence has been established.
