Evaluation of Adjuvant Radiation and Endocrine Therapy in Elderly Patients with Early-Stage Breast Cancer

Abstract

<h3>Purpose/Objective(s)</h3> Several prospective trials demonstrated the feasibility of the omission of adjuvant radiation therapy (RT) among elderly breast cancer patients without worsening overall mortality. However, 50-70% of patients could not finish the full course of adjuvant ET, and select elderly patients may be at risk for undertreatment and tumor recurrences. This study compares the survival outcome of various adjuvant therapies in elderly patients with breast cancer. <h3>Materials/Methods</h3> The National Cancer Database (NCDB) was queried for female patients above 65 years old, diagnosed between 2010 and 2015 with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative, pT1-2N0 (tumor size up to 3 cm) breast cancer who underwent BCS followed by either adjuvant RT, ET, or both. Primary endpoint was overall survival (OS), evaluated by Kaplan-Meier method, log-rank test, and Cox multivariable analysis. Propensity score matching was used to address selection bias. <h3>Results</h3> A total of 16494 patients with a median age of 69 (interquartile range [IQR] 67-73) were analyzed, including 814, 1425, and 14255 patients treated with RT, ET, or both, respectively. On Cox multivariable analysis, ET alone was not associated with improved survival outcome (hazards ratio [HR] 1.00, 95% confidence interval [CI] 0.73-1.38, <i>P</i> = 1.00) compared to RT alone. However, RT combined with ET was associated with improved OS (HR 0.59, 95% CI 0.45-0.76, <i>P</i> < 0.001) compared to RT alone. When propensity score matching was performed, 424 and 683 pairs were matched for RT vs ET alone and RT vs RT and ET. All patient and tumor characteristics were well balanced. There was no difference in OS between RT and ET alone (HR 0.99, 95% CI 0.60-1.65, <i>P</i> = 0.97), while RT combined with ET was associated with improved OS (HR 0.54, 95% CI 0.34-0.86, <i>P</i> = 0.009). <h3>Conclusion</h3> RT alone may be considered as an alternative option in elderly patients who decline or may not tolerate ET, while RT combined with ET may be preferred for select elderly patients.