The Association Between Surgical Axillary Staging, Adjuvant Treatment Use and Survival in Older Women with Early Stage Breast Cancer: A Population-Based Study

Background Choosing Wisely guidelines recommend against surgical axillary staging (AS) in women ≥70 years with ER+/HER2– early stage breast cancer (BC). This study examined the impact of AS omission on survival in older patients with BC. Methods This was a population-based cohort study using health administrative data in Ontario, Canada. We identified women aged 65–95 years who underwent surgery for Stage I/II BC between 2010 and 2016. Patients were weighted by propensity scores for receipt of AS that included patient and disease characteristics using overlap weights. Association with overall survival (OS) was calculated using weighted Cox models, and breast cancer-specific survival (BCSS) was calculated using weighted Fine and Gray models, adjusting for biomarkers and adjuvant treatments. Adjuvant treatment receipt was modelled with weighted log-binomial models. Results Among 17,370 older women, the 1771 (10.2%) who did not undergo AS were older, more comorbid, and less likely to undergo mastectomy. Women who did not undergo AS were less likely to receive adjuvant chemotherapy (RR 0.68, 95% CI 0.57–0.82), endocrine therapy (RR 0.85, 95% CI 0.81–0.89) or radiotherapy (RR 0.69, 95% CI 0.65–0.74). After weighting and adjustment, there was no significant difference in BCSS (sdHR 0.98, 95% CI 0.77–1.25), but women who did not undergo AS had worse OS (HR 1.14, 95% CI 1.04–1.25). The results among 6215 ER+/HER2– women ≥70 years undergoing SLNB vs no AS were similar. Conclusions The omission of AS in older women with early stage BC was not associated with adverse BCSS, although OS was worse.