Harms of screening mammography for breast cancer in Japanese women

The US Preventative Services Task Force assesses the efficacy of breast cancer screening by the sum of its benefits and harms, and recommends against routine screening mammography because of its relatively great harms for women aged 40-49 years. Assessment of the efficacy of screening mammography should take into consideration not only its benefits but also its harms, but data regarding those harms are lacking for Japanese women. In 2008 we collected screening mammography data from 144,848 participants from five Japanese prefectures by age bracket to assess the harms [false-positive results, performance of unnecessary additional imaging, fine-needle aspiration cytology (FNA), and biopsy and its procedures]. The rate of cancer detected in women aged 40-49 years was 0.28%. The false-positive rate (9.6%) and rates of additional imaging by mammography (5.8%) and ultrasound (7.3%) were higher in women aged 40-49 years than in the other age brackets. The rates of FNA (1.6%) and biopsy (0.7%) were also highest in women aged 40-49 years. However, they seemed to be lower than the rates reported by the Breast Cancer Surveillance Consortium (BCSC) and other studies in the US. The results, although preliminary, indicate the possibility that the harms of screening mammography for Japanese women are less than those for American women.