General Surgery Resident, PhD Candidate Department of Surgery, University of Toronto
Introduction: The use of axillary staging (AS), including sentinel lymph node biopsy, in women ≥ 70 years with early-stage breast cancer is controversial. Randomized controlled trials have not shown AS improves survival, but evidence from observational studies has been mixed and most patients continue to receive staging. We aimed to determine if AS is associated with survival in elderly women.
Methods: We performed a retrospective cohort study using the SEER registry. Women 70 years and older diagnosed with invasive breast cancer (T1 – T2) between 2005 and 2015 were included. To adjust for confounders we used overlap propensity score weighting. Overall survival (OS) was determined and hazard ratios (HRs) reported with 95% confidence intervals (CIs). Breast cancer-specific survival (BCSS) was determined using competing risks analysis and subdistribution hazard ratios (sdHRs) reported. Models were additionally adjusted for the receipt of adjuvant chemotherapy and radiotherapy.
Results: 144,329 women ≥70 years were included, of whom 22,621 (15.7%) did not receive AS. Baseline characteristics between the two groups, including age, surgery type, tumor size/grade, and receptor status were well balanced after overlap propensity score weighting. Compared to those who had staging, women who did not undergo AS were significantly less likely to receive chemotherapy (RR 0.58, 95% CI 0.54–0.62) or radiotherapy (RR 0.53, 95% CI 0.52–0.54), and had significantly worse OS (HR 1.22, 95% CI 1.19–1.25), and BCSS (sdHR 1.14, 95% CI 1.08–1.21). In a subgroup of patients with HER-2 negative, ER positive tumors, women who did not receive AS similarly had worse BCSS (sdHR 1.17, 95% CI 1.05–1.31).
Conclusions: Our study suggests women ≥70 years with early-stage breast cancer who do not receive AS experience worse outcomes, including breast cancer-specific survival, and are less likely to receive adjuvant treatments. Reasons for this disparity require further research.