Implications of omitting sentinel lymph node biopsy on adjuvant decision making for patients with small breast cancers

Background: Selective omission of sentinel lymph node biopsy (SLNB) in patients with early breast cancer limits surgical morbidity. Adoption of this strategy relies on multidisciplinary consensus. Understanding how SLNB omission influences guideline-based adjuvant treatment decisions, and the proportion of patients impacted, can help guide decision-making. Patients and methods: Data from the National Cancer Database (2018–2020) was used to estimate the proportions of patients with cT1N0 hormone receptor–positive breast cancer for whom adjuvant chemotherapy, CDK4/6 inhibitor therapy, and regional nodal irradiation decisions would be impacted by the absence of lymph node pathology if national treatment guidelines were followed. Because OncotypeDX score is essential to adjuvant decision-making when SLNB is omitted, inverse probability weighting was used to estimate the proportions of interest had all individuals undergone OncotypeDX testing. Results: There were 119,312 included patients, with an average age of 63 years, 96,454 (80.8%) having invasive ductal histology, and 52,222 (43.8%) having cT1c tumors. The number of patients with SLNB positivity was 13,211 (11.1%). Among postmenopausal women, 7.9% (95% CI, 7.7–8.1) would have had at least one adjuvant decision impacted by the absence of lymph node pathology. For premenopausal women, the affected proportion was 13.7% (95% CI, 13.0–14.7). When ribociclib decision-making was not considered, these estimates were 2.5% for postmenopausal women and 12.6% for premenopausal women. Conclusions: SLNB omission has a small – but not negligible – influence on adjuvant decision making in postmenopausal women, whereas a larger proportion of premenopausal women would be impacted. The reported estimates may inform multidisciplinary decision-making related to SLNB omission.