Ethnic inequities in type of  breast cancer surgery in Aotearoa/New Zealand -  which factors contribute? 

Purpose: Aotearoa/New Zealand (NZ) faces ethnic inequities with respect to breast cancer survival and treatment. This study establishes if there are ethnic differences in i. type of surgery and ii. receipt of radiotherapy (RT) following breast conserving surgery (BCS), among women with early-stage breast cancer in NZ. Methods This analysis used Te Rēhita Mata Ūtaetae (Breast Cancer Foundation National Register), a prospectively maintained database of breast cancers from 2000–2020. Logistic regression models evaluated ethnic differences in type of surgery (mastectomy or BCS) and receipt of RT with sequential adjustment for potential contributing factors. Subgroup analyses by treatment facility type were undertaken. Results Of the 16,228 women included, 74% were NZ European (NZE), 10.3% were Māori, 9.4% were Asian and 6.2% were Pacific. Over one-third of women with BCS-eligible tumours received mastectomy. Asian women were more likely to receive mastectomy than NZE (OR: 1.62; 95% CI: 1.39, 1.90) as were wāhine Māori in the public system (OR: 1.21; 95% CI: 1.02, 1.44) but not in the private system (OR: 0.78; 95% CI: 0.51, 1.21). In women undergoing BCS, compared to NZE, Pacific women overall and wāhine Māori in the private system were respectively 36% and 38% less likely to receive RT (respective OR: 0.64; 95% CI: 0.50, 0.83 and 0.62; 95% CI: 0.39, 0.98). Conclusion A significant proportion of women with early-stage breast cancer underwent mastectomy and significant ethnic inequities exist. NZ guidelines require revisiting to facilitate standardized and equitable surgical management of early-stage breast cancer.