Tumor size is associated with adjuvant chemotherapy benefit in T1N0M0 triple-negative breast cancer: a multicenter and propensity score matched analysis

BACKGROUND: Triple-negative breast cancer (TNBC) is characterized by aggressive phonotypes and relatively poor outcomes. There are controversies on the effect of adjuvant chemotherapy in small (T1N0M0) TNBCs, especially among T1a-b patients. This study evaluated the survival benefit of adjuvant chemotherapy and influential factors in T1N0M0 TNBC patients. METHODS: All T1N0M0 TNBC patients were identified from the Shanghai Jiao Tong University Breast Cancer Database (SJTU-BCDB) between January 2009 and December 2021. Propensity score matched (PSM) was applied to create a matched cohort. We used Kaplan-Meier analysis and Cox regression models to evaluate the associations of adjuvant chemotherapy with breast cancer-free interval (BCFI) and overall survival (OS). Stratified analysis according to different influential factors was also performed. RESULTS: In total, 1,113 T1N0M0 TNBC patients (297 T1a, T1b and 816 T1c) were enrolled, including 928 patients with adjuvant chemotherapy and 185 patients without adjuvant chemotherapy. After matching 441 patients by using PSM analysis, 294 patients with chemotherapy and 147 patients without chemotherapy were identified. Patients with or without chemotherapy had similar BCFI (P=0.241) and OS (P=0.509). However, regarding patients with different tumor sizes, adjuvant chemotherapy could significantly improve BCFI in T1c patients (5-year BCFI: 92.1% vs. 79.5%, P=0.035) but not in T1a-b patients (5-year BCFI: 93.6% vs. 94.6%, P=0.546). No significant difference in OS was observed among patients with different tumor sizes. Subgroup analysis found that only tumor size was significantly associated with adjuvant chemotherapy benefit in terms of BCFI (P(interaction)=0.021) and OS (P(interaction)=0.040). CONCLUSIONS: The survival benefit of adjuvant chemotherapy was significantly associated with tumor size in T1N0M0 TNBC. Benefit of adjuvant chemotherapy was found in T1c, but not in T1a-b patients. Our findings do not support the routine use of chemotherapy in patients with T1a-bN0 TNBC.