Female Breast Cancer Treatment and Survival in South Australia: Results from Linked Health Data
Background: We investigated treatment and survival by clinical and sociodemographic characteristics in South Australia for service evaluation using linked data.Method: Data on invasive female breast cancers (n=13494) 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
... regression, and adjusted sub-hazard ratios (aSHRs) from competing risk regression. Results: Five-year disease-specific survival increased to 91% for 2010-2014. Survival was lower for: ages 70+ years, and lowest for 80+ years (aSHR 2.04, 95%CI 1.69-2.47), compared with ages <50 years; and in the presence of comorbidity (aSHR 2.00, 95%CI 1.06-3.78), higher TNM stage and higher grade. Differences in aSHRs were not found by birth country or residential remoteness, but survival was higher in the least disadvantaged areas (aSHR 0.77, 95%CI 0.65-0.92). Most women had breast surgery (90%) (breast conserving surgery (56%), mastectomy (26%), and both surgery types (9%)), 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. More women from least disadvantaged areas had systemic therapy (aOR 1.43, 95%CI 1.26-1.63). Radiotherapy was less common in outer regional/remote residents compared with major city residents (aOR 0.88, 95%CI 0.78-0.99). Conclusions: High survival from breast cancer in South Australia was comparable to the Australia-wide rate and did not differ by residential remoteness and country of birth. Surgical treatment within 12 months after cancer diagnosis increased during the study period and strongly predicted higher survival. Patients aged 70+ years had lower survival and less treatment, and more trial evidence is needed to optimize trade-offs between benefits and harms in this older age range. Systemic therapy was less for residents from most disadvantaged areas, while radiotherapy was less for residents of outer regional and remote areas.