10-Year axillary recurrence in the RACS SNAC1 randomised trial of sentinel lymph node-based management versus routine axillary lymph node dissection

BACKGROUND: Sentinel node-based management (SNBM) is the international standard of care for early breast cancer that is clinically node-negative based on randomised trials comparing it with axillary lymph node dissection (ALND) and reporting similar rates of axillary recurrence (AR) without distant disease. We report all ARs, overall survival, and breast cancer-specific survival at 10-years in SNAC1. METHODS: 1.088 women with clinically node-negative, unifocal breast cancers 3 cm or less in diameter were randomly assigned to either SNBM with ALND if the sentinel node (SN) was positive, or to SN biopsy followed by ALND regardless of SN involvement. RESULTS: First ARs were more frequent in those assigned SNBM rather than ALND (11 events, cumulative risk at 10-years 1·85%, 95% CI 0·95–3.27% versus 2 events, 0·37%, 95% CI 0·08–1·26%; HR 5·47, 95% CI 1·21–24·63; p = 0·013). Disease-free survival, breast cancer-specific survival, and overall survival were similar in those assigned SNBM versus ALND. Lymphovascular invasion was an independent predictor of AR (HR 6·6, 95% CI 2·25–19·36, p < 0·001). CONCLUSION: First ARs were more frequent with SNBM than ALND in women with small, unifocal breast cancers when all first axillary events were considered. We recommend that studies of axillary treatment should report all ARs to give an accurate indication of treatment effects. The absolute frequency of AR was low in women meeting our eligibility criteria, and SNBM should remain the treatment of choice in this group. However, for those with higher-risk breast cancers, further study is needed because the estimated risk of AR might alter their choice of axillary surgery.