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

Document Type : Research Articles


1 Discipline of Behavioural and Social Sciences in Health, The University of Sydney, Australia.

2 Discipline of Medical Radiation Sciences, The University of Sydney, Australia.


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


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