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.