Multidisciplinary Management of the Axilla in Patients with cT1-T2 N0 Breast Cancer Undergoing Primary Mastectomy: Results from a Prospective Single-Institution Series

Background: The after mapping of the axilla: radiotherapy or surgery (AMAROS) trial concluded that for patients with cT1-2 N0 breast cancer and one or two positive sentinel lymph nodes (SLNs), axillary radiotherapy (AxRT) provides equivalent locoregional control and a lower incidence of lymphedema compared with axillary lymph node dissection (ALND). The study prospectively assessed how often ALND could be replaced by AxRT in a consecutive cohort of patients undergoing mastectomy for cT1-2 N0 breast cancer. Methods: In November 2015, our multidisciplinary group agreed to omit routine intraoperative SLN evaluation for cT1-2 N0 patients undergoing upfront mastectomy and potentially eligible for postmastectomy radiation therapy (PMRT), including those 60 years of age or younger and those older than 60 years with high-risk features. Patients with one or two positive SLNs on final pathology were reviewed to determine whether PMRT including the full axilla was an appropriate alternative to ALND. Results: From November 2015 to December 2016, 154 patients met the study criteria, and 114 (74%) formed the final study cohort. Intraoperative SLN evaluation was omitted for 76 patients (67%). Of these patients, 20 (26%) had one or two positive SLNs, and 14 of these patients received PMRT + AxRT as an alternative to ALND. Three patients returned for ALND, and three patients were observed. On univariate analysis, tumor size, LVI, number of positive lymph nodes, and receipt of chemotherapy were associated with receipt of PMRT. Conclusions: For the majority of patients with one or two positive SLNs, ALND was avoided in favor of PMRT + AxRT. With appropriate multidisciplinary strategies, intraoperative evaluation of the SLN and immediate ALND can be avoided for patients meeting the AMAROS criteria and eligible for PMRT.