Changes in survival after breast cancer: improvements in diagnosis or treatment?

We have compared 5-year survival rates in two cohorts of women diagnosed with breast cancer in Brisbane, Australia, between 1981-1984 and 1990-1994. Tumours diagnosed in the early 1990s were significantly smaller and less likely to have nodal involvement than those diagnosed 10 years earlier (P<0.0001). The size difference was particularly striking for women aged over 50 at diagnosis, those targeted for screening. Five-year survival was greater among women diagnosed in the 1990s (84% vs. 74%; hazard ratio (HR) 0.61, 95% confidence interval (CI) 0.46-0.81). After adjusting for the effects of tumour size and nodal status this difference was reduced, but women diagnosed more recently still showed improved survival (HR 0.75; 95% CI 0.56-1.01) and disease-free survival (HR 0.72; 0.56-0.92) at 5 years. This suggests that both earlier diagnosis and changes in breast cancer treatment have contributed to improved breast cancer survival.