Quality control of breast cancer screening in Yokohama city for women in their 40 s

Biennial screening mammography for breast cancer detection has been carried out in Yokohama City for women aged 50 years and older since October 2001. In three and a half years 49,795 eligible women have been screened, 123 have been diagnosed as having cancer, and the cancer detection rate has been 0.25%. Since 73% of the diagnosed cancers were classified as stage 0 and I, this screening system is considered to have contributed to improving the prognosis of the examines. With regard to quality control, although the rate of women requiring a detailed re-examination has been reduced significantly from 19.1% to 6.9%, the positive predictive value of less than 4% is still insufficient. It is therefore considered that there are some problems with detailed re-examinations. Since screening mammography for breast cancer was extended to women aged 40-49 years in Yokohama City in July 2005, the rate of cancer not detected by mammography was examined in age cohorts of five years among 138 women who were clinically diagnosed as having breast cancer. Because 12.2% of women aged 44 years and younger had no findings on mammography, and cancer was detected in 87.5% of these women by ultrasonography (US), it is recommended that US should be added to mammography for breast cancer examination at this age. (author)