Use of chemotherapy and loco-regional therapy for stage IA triple-negative breast cancer and their association with oncologic outcomes: A cancer registry study.

Abstract

524 Background: We aimed to evaluate the role of adjuvant chemotherapy and loco-regional therapy for stage IA (pT1, pN0) triple-negative breast cancer (TNBC) in a real-world setting. Methods: We identified patients with pT1, pN0 TNBC diagnosed between 2009 and 2021 within the clinical cancer registry of Baden-Wuerttemberg, Germany. Overall survival (OS) was assessed using Kaplan-Meier statistics and multivariate Cox regression models (adjusted for age, use of chemotherapy, local therapy (breast conserving therapy [breast conserving surgery + radiotherapy] vs. mastectomy), and tumor histologic subtype). Results: A total of 1191 patients with a median follow-up of 43.8 months were identified: 0.9% (11 of 1191) with pT1mi stage, 10.0% (119 of 1191) with pT1a, 24.0% (286 of 1191) with pT1b, and 65.0% (775 of 1191) with pT1c. Use of adjuvant chemotherapy was 9.1% (1 of 11) in pT1mi stage, 41.2% (49 of 119) in pT1a, 66.8% (191 of 286) in pT1b, and 69.8% (541 of 775) in pT1c. Multivariate Cox regression analysis revealed no significant influence for the use of adjuvant chemotherapy on OS in pT1a and pT1b patients (for pT1a HR 1.27, 95% CI 0.19 to 8.50, for pT1b HR 1.07, 95% CI 0.50 to 2.30) but for patient age in the pT1b group (HR 4.71, 95% CI 2.26 to 9.8, for age ≥70 vs. <70 years). For pT1c patients, there was significant influence for the use of adjuvant chemotherapy on OS (HR 0.55, 95% CI 0.38 to 0.8), for local therapy (HR 0.41, 95% 0.25 to 0.69, for breast conserving therapy vs. mastectomy only), and patient age (HR 2.33, 95% CI 1.61 to 3.39 for age ≥70 vs. <70 years). Notably, for pT1c patients aged <70years, local therapy (HR 0.32, 95% CI 0.15-0.69), in favor of breast conserving therapy) but not use of chemotherapy (HR 1.11, 95% CI 0.56-2.19) was associated with OS. Conclusions: This data suggests that OS in stage IA TNBC is strongly influenced by local therapy and patient age, but not use of chemotherapy. Larger studies with longer-term follow-up are welcomed to fully inform this discussion.