Survival Benefit of Adjuvant Chemotherapy in Node-Positive Breast Cancer With a 21-Gene Recurrence Score of 14 to 25: A Real-World Study Based on the Inverse Probability of Treatment Weighting Method

Abstract

IntroductionThe role of recurrence score in predicting the benefits of adjuvant chemotherapy for lymph-node-positive breast cancer remains uncertain. We studied chemotherapy usage in patients with 1 to 3 positive lymph nodes and a recurrence score (RS) of 25 or lower to assess changes in clinical practice based on the RxPONDER trial. MethodsA retrospective study using the SEER database identified female patients diagnosed with ER-positive, HER2-negative breast cancer, 1 to 3 positive lymph nodes, and an RS of 25 or lower between 2010 and 2015. Patients were divided into nonchemotherapy and chemotherapy groups, with propensity score weighting to balance clinicopathologic factors. ResultsAmong 7965 patients, 5774 (72.5%) were in the nonchemotherapy group, while 2191 (27.5%) were in the chemotherapy group. Median follow-up was 39 months. Breast cancer accounted for 67 deaths, while 128 deaths were due to other causes. The weighted 5-year overall survival (OS) rates were 95.7% for the nonchemotherapy group and 97.2% for the chemotherapy group. For high-risk patients, the weighted 5-year OS rates were 95.2% and 97.0% for the nonchemotherapy and chemotherapy groups, respectively, with a significant absolute difference of 1.8% (P = .014). Multivariate analysis showed a significant difference in weighted hazard ratios for OS between the nonchemotherapy and chemotherapy groups in high-risk patients (hazard ratio: 0.64; 95% CI: 0.48-0.86). However, there were no significant differences in weighted hazard ratios for lower-risk patients, and similar results were observed for breast cancer-specific survival (BCSS). ConclusionPatients with ER-positive, HER2-negative breast cancer and 1 to 3 positive lymph nodes, assessed by a 21-gene RS of 0 to 25, exhibited heterogeneous prognosis. Adjuvant chemotherapy provided a significant survival benefit, especially for patients with RS of 14 to 25, particularly those with invasive ductal carcinoma (IDC) and 2 to 3 positive lymph nodes.