Aboriginal and Torres Strait Islander females and survival from breast cancer.

Abstract

Background Despite access to universal health care, Aboriginal and Torres Strait Islander females (hereafter respectfully referred to as Aboriginal) in Australia have higher breast cancer incidence and mortality rates. We investigated factors contributing to these survival disparities. Methods Aboriginal females (n=395; 0.7%) and non-Aboriginal females (n=57 618; 99.3%) with breast cancer were identified from Victoria, Australia. Clinical, pathological, demographic, and socioeconomic variables were analyzed. Endpoints were all-cause and breast cancer-specific mortality. Hazard ratios (HR) were estimated using Cox regression. Tumor-infiltrating lymphocytes (sTILs) were evaluated from a subset of Aboriginal females and compared to females in TCGA. Results Registry data revealed that Aboriginal females were younger (P<0.001), had more advanced stage disease (P=0.007), were more likely to live in non-metropolitan areas (P<0.001) and in areas of greater disadvantage (P<0.001) compared to other females, at diagnosis. Age-adjusted multivariate analysis revealed a higher all-cause mortality risk (HR 1.27, 95%CI 1-1.61) for Aboriginal females, but this risk diminished for breast cancer specific mortality and after adjustment for stage and grade. Breast cancers from Aboriginal females had significantly reduced sTILs in the luminal and triple-negative subtypes, compared to TCGA. Conclusions Mortality for females with breast cancer was influenced by socio-economic, geographic and clinical factors. Notably, Aboriginal females with tumour features typically associated with favourable outcomes, experienced poorer outcomes. The reduced immune infiltrate warrants further investigation. Impact These findings highlight the need to address socioeconomic inequities and ensure culturally safe cancer care. Further research should explore biological and environmental factors influencing outcomes for Australian Aboriginal females.