Purpose: One of the Society of Surgical Oncology Choosing Wisely guidelines recommends avoiding routine sentinel lymph node (SLN) surgery in clinically node-negative women ≥70 years of age with hormone receptor-positive (HR+) breast cancer. We sought to assess the impact of tumor stage and grade on nodal positivity, and to develop a model to identify patients at low-risk of nodal positivity to aid adoption of the guideline. Methods: We identified women ≥70 years of age with HR+ cN0 invasive breast cancer in the National Cancer Database (NCDB; 2010–2013) and examined the impact of tumor stage and grade on nodal positivity to identify low-risk combinations. A multivariable logistic regression model was developed to incorporate additional factors. The area under the curve (AUC) and relative risks (RR) were used to assess performance. Results: Among 71,834 cases, the pathologic nodal positivity (pN+) rate was 15.3%. We identified low-risk criteria as grade 1, cT1mi-T1c (≤2.0 cm), or grade 2, cT1mi-T1b (≤1.0 cm), with pN+ rates of 7.8% compared with 22.3% in patients not meeting these criteria (RR 2.86, p < 0.001). On multivariable analysis, factors associated with pN+ status included clinical T stage, grade, and histology (each p < 0.001). The resulting model had AUC 0.70 and identified women with low predicted probability (<10%) of positive nodes, of whom 6.3% were pN+, versus 21.2% in those with predicted probability ≥10% (RR 3.34, p < 0.001). Conclusion: The simple clinical rule (grade 1, cT1mi-T1c, or grade 2, cT1mi-T1b), as well as the predictive model, both identify women at low risk of nodal positivity where SLN surgery can be omitted.
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