Rationale Treatment guidelines recommend a more conservative surgical approach than mastectomy for early stage breast cancer and a stronger emphasis on adjuvant therapy. Registry data at South Australian teaching hospitals have been used to monitor survivals and treatment in relation to these guidelines.Aims and objectives To use registry data to: (1) investigate trends in survival and treatment; and (2) compare treatment with guidelines.Methods Registry data from three teaching hospitals were used to analyse trends in primary courses of treatment of breast (...) cancers during 1977–2003 (n = 4671), using univariate analyses and multiple logistic regression. Disease-specific survivals were analysed using Kaplan–Meier product limit estimates and multivariable Cox proportional hazards regression.Results The 5-year survival was 79.9%, but with a secular increase, reaching 83.6% in 1997–2003. The relative risk of death (95% confidence limits) was 0.74 (0.62, 0.88) for 1997–2003, compared with previous diagnoses, after adjusting for tumour node metastasis stage, grade, age and place of residence. Treatment changes included an increase in conservative surgery (as opposed to mastectomy) from 51.7% in 1977–1990 to 76.8% in 1997–2003 for stage I (P < 0.001) and from 31.1% to 52.2% across these periods for stage II (P < 0.001). Adjuvant radiotherapy also became more common (P < 0.001), with 20.6% of patients receiving this treatment in 1977–1990 compared with 60.7% in 1997–2003. Radiotherapy generally was more prevalent when conservative surgery was provided, although also relatively common in mastectomy patients when tumour diameters exceeded 50 mm or when there were four or more involved nodes. The proportion of patients receiving chemotherapy increased (P < 0.001), from 19.6% in 1977–1990 to 36.9% in 1997–2003, and the proportion having hormone therapy also increased (P < 0.001), from 34.3% to 59.4% between these periods.Conclusions Survivals appear to be increasing and treatment trends are broadly consistent with guideline directions, and the earlier research on which these recommendations were based. (shrink)