This analysis involved 13,657 women diagnosed with primary invasive breast cancer between January 2000 and June 2014 who were in the Auckland and Waikato Breast Cancer Registries. Compared with other ethnic groups, the 1,281 Māori and 897 Pacific women in this analysis were younger, more likely to reside in deprived neighbourhoods and to have co-morbidities, and less likely to be diagnosed through screening and with early stage cancer, to be treated in a private care facility, to receive timely cancer treatment, and to receive breast conserving surgery. In Cox regression modelling, Māori and Pacific women had a higher risk of excess mortality from breast cancer (age and year of diagnosis adjusted HR 1.76; 95% CI, 1.51 to 2.04 for Māori and 1.97; 95% CI, 1.67 to 2.32 for Pacific women), of which 75% and 99%, respectively, were explained by baseline differences. The most important contributor was late stage at diagnosis. Other contributors included neighbourhood deprivation, mode of diagnosis, type of health care facility providing the primary cancer treatment and type of locoregional therapy.
