Sentinel Node Biopsy Alone or With Axillary Dissection in Breast Cancer Patients After Primary Chemotherapy: Long-Term Results of a Prospective Interventional Study.

OBJECTIVE: To ascertain, in cN0/1 breast cancer patients given primary chemotherapy followed by sentinel node biopsy (SNB), whether SNB alone is adequate axillary treatment if the sentinel nodes (SNs) are clear (pN0). SUMMARY BACKGROUND DATA: 2020 guidelines do not recommend SNB in most cN1 patients with clear SNs after primary chemotherapy because the high SNB false negative rate might lead to poorer outcomes. METHODS: We prospectively assigned SNB after primary chemotherapy to 353 consecutive cT2 cN0/1 patients, median age 47 years (range 22-76) treated from 2007 to 2015. If the SNs were pN0, patients generally received no further axillary treatment (SNB only); if the SNs were pN1, completion axillary dissection (AD) (SNB + AD) was usually performed. Primary outcomes were overall (OS) and disease-free (DFS) survival in SNB only versus SNB + AD patients, assessed by Kaplan-Meier and compared using log-rank test, with use of propensity scores to account for bias due to nonrandom assignment to SNB versus SNB + AD. RESULTS: Median follow-up was 108 months, interquartile range 66 to 136. OS and DFS did not differ significantly between the groups by propensity score- weighted comparison: 10-year OS 89% [95% confidence interval (CI): 81%- 99%] in SNB only patients versus 86% (95%CI: 78%-95%) in SNB + AD patients; 10-year DFS 79% (95%CI: 68%-92%) versus 69% (95%CI: 58%-81%). No SNB-only patient developed axillary failure. CONCLUSIONS: cT2 cN0/1 patients whose SNs are disease-free (pN0) after primary chemotherapy can be offered SNB (with no further axillary treatment if the SNs are negative), irrespective of axillary status beforehand, without affecting OS or DFS.