Adjuvant Chemotherapy in Early Triple-Negative Breast Cancer (T1a-c N0M0): A Systematic Review and Meta-Analysis

Abstract

Triple-negative breast cancer (TNBC) is an aggressive subtype with limited treatment options and a high risk of early metastasis. While adjuvant chemotherapy (AdjCT) is standard for TNBC, its benefit in small, node-negative tumors (T1a, T1b, T1c) remains uncertain. This meta-analysis evaluates the survival impact of AdjCT in early-stage TNBC, focusing on overall survival (OS), breast cancer-specific survival (BCSS), and disease-free survival (DFS).

A comprehensive search was conducted in PubMed, the Cochrane Library, and Embase, yielding a total of 2089 studies. Hazard ratios (HR) and odds ratios (OR) were estimated using a random-effects model with 95% confidence intervals (CI). Heterogeneity was assessed with I², considering P < .05 and I² > 25% as significant. Our meta-analysis included 12 cohort studies, comprising a total of 48,371 patients, of whom 32,341 were included in the AdjCT group. AdjCT improved OS overall (HR: 0.75; 95% CI, 0.64-0.88; P < .001; I² = 83%), in T1b (HR: 0.73; P = .013; I² = 74%) and T1c tumors (HR: 0.73; P = .19; I² = 89%), but not in T1a (HR: 0.88; P = 0.646). BCSS showed a significant overall benefit (HR: 0.21; P = .042; I² = 98%), but no difference in T1a, T1b, or T1c subgroups. AdjCT also significantly improved 5-year DFS (OR: 2.08; 95% CI, 1.32-3.29; P = .002; I² = 0%). AdjCT improves OS in early-stage TNBC, particularly in T1b and T1c tumors, while significantly enhancing BCSS and DFS. No survival benefit was observed in T1a tumors, emphasizing the need for stage-based AdjCT decisions.