Abstract P2-10-16: Breast cancer treatment patterns and outcomes for Australian women by indigenous status and remoteness of residence
Authors: Redfern Andrew David , Khan Azim , Spalding Lisa J , Martin Hilary 
Published: March 2020

In Australia, incidence of breast cancer is lower but mortality risk is substantially higher in Indigenous relative to non-Indigenous women. Substantial detriment has been found to remain even after compensating for social class and stage of disease with risk of dying still being more than double. At almost one million square miles many patients in Western Australia have to travel for several days for single cycles of treatment in the capital Perth. Indigenous patients on average live in significantly more remote locations than non-Indigenous patients. We have also identified greater incidences of higher risk breast cancer sub-types in the Indigenous population including luminal B and HER2-enriched cancers which require more frequent and longer IV treatment schedules. Research is entirely lacking on systemic treatment disparities in adjuvant and metastatic settings, differences in follow-up and secondary screening protocols by Indigenous status in Australia. Here we set out to define patterns of offered, accepted, and completed treatment with a view to addressing service gaps for disadvantaged populations. An initial cohort of 100 patients comprising 1:1 matched Indigenous and non-Indigenous patients from across WA was obtained from the WA Cancer Registry. Registry data was supplemented with data from the Death Registry, individual medical records from hospitals and family practitioners, state results systems and pharmacy records. Initial surgery performed, radiotherapy delivered and rates of offering, accepting, commencing and completing chemotherapy, HER2-targeted and endocrine therapy were collated by sub-type and stage. Here initial results on treatment of early disease are presented. At the time of writing, data for 37 Indigenous and 33 non-Indigenous breast cancer patients are available. 46% of the cohort are deceased with a median follow-up of 13.2 years. 10-year survival was higher for patients in the metro area than regional or remote patients (79 v 58%, p=0.03) and for non-Indigenous relative to Indigenous patients (84 v 53%, p=0.003). Considering treatment pattern by Indigenous status, no significant differences were observed. Proportionally more Indigenous patients underwent mastectomy relative to conservative surgery (44 v 29 %), a difference observed across tumour sizes. Rate of axillary clearance relative to lymph node (LN) biopsy was similar (48 v 44%) but interestingly was numerically higher for Indigenous women where LNs were involved (99 v 88%). Post-operative radiotherapy was delivered in cases of conservative surgery or locally advanced disease in 87 and 93% of Indigenous and non-Indigenous cases with 9 and 7% of patients declining radiotherapy. For chemotherapy similar proportions of Indigenous and non-Indigenous patients declined offered adjuvant treatment (17 v 19%). Once commenced chemotherapy was completed in similar proportions (89 v 92%). 96% of both groups with estrogen receptor positive tumours were offered adjuvant endocrine therapy. However, the rate of declining or stopping endocrine therapy was numerically higher in Indigenous women (33 v 16%, p=0.12). To conclude, in this small cohort outcomes were significantly inferior, both for Indigenous women and for women living in regional and remote areas. Rates of delivery of local and adjuvant systemic therapy were similar. Rates of offering endocrine treatment were not different but a trend to lower acceptance or compliance with endocrine treatment was seen in Indigenous women that could potentially be addressed by improved patient information, expanded follow-up and toxicity management.

Citation Format: Andrew David Redfern, Azim Khan, Lisa J Spalding, Hilary Martin. Breast cancer treatment patterns and outcomes for Australian women by indigenous status and remoteness of residence [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-10-16.