Female breast cancer treatment and survival in South Australia: Results from linked health data

Objective: We investigated treatment and survival by clinical and sociodemographic characteristics for service evaluation using linked data. Method: Data on invasive female breast cancers (n = 13,494) from the South Australian Cancer Registry (2000–2014 diagnoses) were linked to hospital inpatient, radiotherapy and universal health insurance data. Treatments ≤12 months from diagnosis and survival were analysed, using adjusted odds ratios (aORs) from logistic regression, and adjusted sub-hazard ratios (aSHRs) from competing risk regression. Results and conclusion: Five-year disease-specific survival increased to 91% for 2010–2014. Most women had breast surgery (90%), systemic therapy (72%) and radiotherapy (60%). Less treatment applied for ages 80+ vs <50 years (aOR 0.10, 95% CI 0.05–0.20) and TNM stage IV vs stage I (aOR 0.13, 95% CI 0.08–0.22). Surgical treatment increased during the study period and strongly predicted higher survival. Compared with no surgery, aSHRs were 0.31 (95% CI 0.26–0.36) for women having breast-conserving surgery, 0.49 (95% CI 0.41–0.57) for mastectomy and 0.42 (95% CI 0.33–0.52) when both surgery types were received. Patients aged 80+ years had lower survival and less treatment. More trial evidence is needed to optimise trade-offs between benefits and harms in these older women. Survival differences were not found by residential remoteness and were marginal by socioeconomic status.