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.

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.

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).

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.