Should patients with hormone receptor–positive, HER2–negative breast cancer and one or two positive sentinel nodes undergo axillary dissection to determine candidacy for adjuvant abemaciclib?

Background: The monarchE trial demonstrated improved outcomes with the use of adjuvant abemaciclib in patients with high-risk hormone receptor–positive, HER2–negative (HR+/HER2–) breast cancer defined as ≥4 positive lymph nodes (+LNs) or one to three +LNs with one or more additional high-risk features (HRFs). The proportion of patients with one or two positive sentinel lymph nodes (+SLNs) without HRFs who had ≥4 +LNs at the time of completion axillary lymph node dissection (cALND), and who therefore qualified for receipt of abemaciclib, was investigated. Methods: Females with pathologically node-positive nonmetastatic HR+/HER2– breast cancer stratified by the number of +SLNs and +LNs and the presence of one or more HRFs were identified from the National Cancer Database (2018–2019). The proportion of patients meeting the criteria for abemaciclib both before and after ALND was assessed. Results: Of the 22,048 patients identified, 1578 patients underwent upfront surgery, had one or two +SLNs without HRFs, and went on to cALND. Only 213 (13%) of these patients had ≥4 +LNs; thus, cALND performed solely to determine abemaciclib candidacy would have constituted surgical overtreatment in 1365 patients (87%). When stratified by the number of +SLNs, only 10% of those with one +SLN and 24% of those with two +SLNs had ≥4 +LNs after cALND, which meets the criteria for abemaciclib. Conclusions: Patients with one +SLN without HRFs are unlikely to have ≥4 +LNs and should not be subjected to the morbidity of ALND in order to inform candidacy for abemaciclib. An individualized multidisciplinary discussion should be undertaken about the risk:benefit ratio of ALND and abemaciclib for those with two +SLNs.