This study explored differences in rates of screen-detected breast cancer by ethnicity and socioeconomic deprivation in a cohort of screening age women, and sought to determine the contribution of these differences to ethnic and socioeconomic inequities in breast cancer survival among Māori and New Zealand European women. Records from the Waikato Breast Cancer Register and the National Screening Database identified all screening age women with newly diagnosed breast cancer (50–64 years up to June 2004 and 45–69 years from July 2005 onwards, as defined by the New Zealand National Breast Cancer Screening Programme) between 1 January 1999 and 31 December 2012 in the Waikato area. Stage at diagnosis and survival were compared for screen-detected (n=1106) and non-screen-detected (n=740) breast cancer by ethnicity and socioeconomic status. Indigenous Māori women were significantly more likely to be diagnosed with more advanced cancer compared with New Zealand European women (OR1.51) and approximately a half of this difference was explained by lower rate of screen-detected cancer for Māori women. For non-screen-detected cancer, Māori had significantly lower 10-year breast cancer survival compared with New Zealand Europeans (46.5% vs 73.2%) as did most deprived compared with most affluent socioeconomic quintiles (64.8% vs 81.1%). No significant survival differences were observed for screen-detected cancer by ethnicity or socioeconomic deprivation.
