Background: Current guidelines recommend postmastectomy radiotherapy (PMRT) for patients with ≥4 positive lymph nodes and suggest strong consideration of PMRT in those with 1–3 positive nodes. These recommendations were incorporated into a Commission on Cancer quality measure in 2014. However, national adherence with these recommendations is unknown. Our objectives were to describe PMRT use in the United States in patients with stage I to III invasive breast cancer and to examine possible factors associated with the omission of PMRT. Methods: From the National Cancer Data Base, 753,536 mastectomies at 1123 hospitals were identified from 1998 to 2011. PMRT use over time was examined using random effects logistic regression analyses, adjusting for patient, tumor, and hospital characteristics. Analyses were stratified by nodal status (≥4 nodes positive, 1–3 nodes positive, node negative). Results: The proportion of patients receiving PMRT increased from 1998 to 2011 (>4 positive nodes: 56.2 to 66.6 %; 1–3 positive nodes: 28.0 to 39.1 %; node-negative: 8.3 to 10.0 %, p < 0.001 for all). In adjusted analyses, patients with ≥4 positive nodes were more likely to have PMRT omitted if they had smaller tumors. Patients with 1–3 positive nodes were more likely to have PMRT omitted if they had lower grade or smaller tumors. Irrespective of patients’ nodal status, PMRT utilization rates decreased as age increased. Conclusions: Though PMRT rates increased over time in patients with ≥4 and 1–3 positive nodes, PMRT in patients with ≥4 positive nodes remains underutilized. Feedback to hospitals using the new Commission on Cancer PMRT measure may help to improve adherence rates.
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