Mammographic Breast Density of Japanese Women Living in Australia: Implications for Breast Screening Policy

Abstract

Background: Mammographic Breast Density (MBD) increases breast cancer risk, lowers sensitivity of mammography<br />and is related to ethnicity. This study compared the MBD of Australian women living in Australia (AW), Japanese<br />women living in Japan (JWJ) and Japan-born women living in Australia (JWA). The outcomes have implications for<br />breast screening policies in Australia. Methods: In this cross-sectional study, mammographic images were collected<br />from a total of 677 women who were examined at BreastScreen NSW or Miyata Hospital, Japan. The images were<br />retrospectively evaluated using the 5th edition Breast Imaging-Reporting and Data System (BI-RADS) to assess<br />the level of MBD. Descriptive analyses and binary logistic regressions were performed. Results: More than 65% of<br />AW had low MBD while the majority of JWJ had high MBD. Among AW, low MBD was found in women aged 40-49<br />and 50-59. The MBD of JWA showed a similar pattern to JWJ but with a slightly lower MBD. The great majority of<br />JWA aged 40-49 were found to have high MBD compared to women aged 50-59. JWJ were categorised as high MBD<br />regardless of their age. JWA were 5 times more likely and JWJ were 15 times more likely to have high MBD compared to<br />AW. Conclusion: Mammography screening becomes more effective for JW after migration to Australia. For JWA<br />aged 40-49 years, supplemental screening options are indicated to provide better cancer detection. For AW, screening<br />mammography could be equally as effective for AW aged 40-49 years as for those aged 50-59.