Benefit of Adjuvant Chemotherapy in Node-Negative T1a Versus T1b and T1c Triple Negative Breast Cancer

Abstract Purpose: National Comprehensive Cancer Network guidelines recommend delivery of adjuvant chemotherapy in node-negative triple negative breast cancer (TNBC) if the tumor is > 1 cm and consideration of adjuvant chemotherapy for T1b but not T1a disease. These recommendations are based upon sparse data regarding the role of adjuvant chemotherapy in T1a and T1b node-negative TNBC. Our objective was to clarify the benefits of chemotherapy for patients with T1N0 TNBC, stratified by tumor size.Methods: We performed a retrospective analysis of survival outcomes in an IRB-approved prospectively-maintained database of TNBC patients treated at two academic institutions in the United States from 1999-2018. Primary tumor size, histology, and nodal status were based upon definitive surgical pathology. Mean follow-up was 5.3 years.Results: 756 TNBC cases were analyzed; 258 T1N0 TNBC patients were identified. Adjuvant chemotherapy was delivered to 30.5% of T1a, 64.7% T1b, and 83.9% T1c (p < 0.0001). Factors associated with delivery of adjuvant chemotherapy were age, histology, high-grade disease, and postoperative adjuvant radiation therapy. At a mean follow-up of 5.3 years, increase in overall survival was associated with use of chemotherapy in patients with T1c disease (93.2% v. 75.2% p = 0.008) but not in those with T1a (100% v. 100% p = 0.3778) or T1b (100% v. 95.8% p = 0.2362) disease.Conclusion: Our data support current guidelines indicating benefit from adjuvant chemotherapy in node-negative TNBC associated with T1c tumors but excellent outcomes were observed in cases of T1a and T1b disease, regardless of whether adjuvant chemotherapy was delivered.