Breast cancer characteristics and survival differences between Maori, Pacific and other New zealand women included in the quality audit program of breast surgeons of Australia and New Zealand

Abstract

Background: The Quality Audit (BQA) program of the Breast Surgeons of Australia and New Zealand (NZ) collects data on early female breast cancer and its treatment. BQA data covered approximately half all early breast cancers diagnosed in NZ during roll-out of the BQA program in 1998-2010. Coverage increased progressively to about 80% by 2008. This is the biggest NZ breast cancer database outside the NZ Cancer Registry and it includes cancer and clinical management data not collected by the Registry. We used these BQA data to compare socio-demographic and cancer characteristics and survivals by ethnicity. Materials and Methods: BQA data for 1998-2010 diagnoses were linked to NZ death records using the National Health Index (NHI) for linking. Live cases were followed up to December 2010. Socio-demographic and invasive cancer characteristics and disease-specific survivals were compared by ethnicity. Results: Five-year survivals were 87% for Maori, 84% for Pacific, 91% for other NZ cases and 90% overall. This compared with the 86% survival reported for all female breast cases covered by the NZ Cancer Registry which also included more advanced stages. Patterns of survival by clinical risk factors accorded with patterns expected from the scientific literature. Compared with Other cases, Maori and Pacific women were younger, came from more deprived areas, and had larger cancers with more ductal and fewer lobular histology types. Their cancers were also less likely to have a triple negative phenotype. More of the Pacific women had vascular invasion. Maori women were more likely to reside in areas more remote from regional cancer centres, whereas Pacific women generally lived closer to these centres than Other NZ cases. Conclusions: NZ BQA data indicate previously unreported differences in breast cancer biology by ethnicity. Maori and Pacific women had reduced breast cancer survival compared with Other NZ women, after adjusting for socio-demographic and cancer characteristics. The potential contributions to survival differences of variations in service access, timeliness and quality of care, need to be examined, along with effects of comorbidity and biological factors.