Impact of Adjuvant Chemotherapy on Survival Benefit in T1N0 Triple Negative Breast Cancer Based on SEER Database by Age Group

Abstract

BACKGROUND We aimed to analyze the survival benefit of adjuvant chemotherapy in patients with T1N0M0 triple-negative breast cancer (TNBC) (age-stratified and tumor size-stratified) to guide more precise treatment. METHODS This study recruited 6482 pT1N0M0 TNBC patients from 2010–2015 in the SEER database (*Stat 8.3.6 software). The χ[2] test was used to compare categorical variables between different tumor sizes. OS and BCSS of patients with T1mic, T1a, T1b and T1cN0M0 TNBC were studied and Kaplan-Meier survival curves were plotted for the prognosis of patients receiving versus not receiving chemotherapy stratified by age and tumor size. RESULTS A total of 6482 T1N0M0 TNBC patients were included in this study, with a total of 4244 (65.47%) patients receiving adjuvant chemotherapy and 2238 (34.53%) not receiving adjuvant chemotherapy, whose 5-year OS was 92.4% and 85.4% (p < 0.001) and 5-year BCSS was 95.1% and 94.9% (p = 0.46), respectively. Among them, 15.2% (16/105), 24.5% (159/650), 58.7% (1046/1781), and 76.6% (3023/3946) received chemotherapy for T1mic, T1a, T1b, and T1c, respectively. The 5-year OS with and without chemotherapy was 93.3% vs. 94.7% (p = 0.95), 98.7% vs. 94.4% (p = 0.004), 94.8% vs. 87.7% (p < 0.001), and 91.2% vs. 77.0% (p < 0.001), respectively, and the 5-year BCSS was 100% vs. 93.3% (p = 0.026),99.3% vs 98.1% (p = 0.22), 96.9% vs 96.3% (p = 0.36), and 94.3% vs 91.4% (p < 0.001), respectively. Among the T1mic patients, receiving chemotherapy did not improve OS (p = 0.95), but instead decreased BCSS (p = 0.026). When patients were stratified by age, it was found that for age > 65 years, T1a patients receiving chemotherapy did not improve OS and BCSS (p = 0.07, p = 0.45). For T1b patients, receiving chemotherapy at age > 75 years did not improve OS and BCSS (p = 0.065, p = 0.13). For T1c patients, receiving chemotherapy did not improve OS and BCSS at age > 80 years (p = 0.19, p = 0.15). CONCLUSION This study found that adjuvant chemotherapy improved OS but not BCSS in T1N0TNBC patients. T1mic patients receiving chemotherapy did not improve OS but decreased BCSS, T1a and T1b patients adjuvant chemotherapy improved OS but not BCSS. >65 years old T1a, > 75 years old T1b and > 80 years old Tc patients receiving chemotherapy did not improve survival and could be used as a clinical reference for patients exempted from chemotherapy.