Comparison of locoregional recurrence in triple-negative and HER2-positive breast cancer subtype after breast-conserving therapy and modern systemic therapy.

Abstract

112 Background: Triple-negative (basal) and HER2+ subtypes have been associated with increased risk of locoregional recurrence (LRR) in earlier studies of breast-conserving therapy (BCT), in which fewer patients received systemic therapy compared with recent standards, including HER2-targeted therapy. We analyzed whether basal and HER2+ subtypes are independent prognostic factors for LRR in BCT patients treated with modern systemic therapy. Methods: We retrospectively studied 415 patients with invasive breast cancer who received BCT from 1992 to 2009. Axillary surgery was done in 404 patients (97%). Forty eight percent of patients received chemotherapy (anthracycline/taxane 34%, trastuzumab-containing 4%, other 10%). Hormone therapy was given in 67%. Progression-free survival (PFS) and OS were estimated by the Kaplan-Meier method. Rate of LRR was estimated by the method of cumulative incidence allowing for competing risks. The effect of prognostic factors was examined by Fine and Gray’s test. Results: Median follow-up was 60 months. Median age was 54 (26–86). Stage: T1 70%, T2 26.3%, T3 8%; N0 75%, N1 23.5%, N2 1.7%. Receptor status was available in 301 patients to approximate subtypes: 66% Luminal A, 9% Luminal B, and 5% HER2+, and 20% Basal. Overall, there were 11 LRR, 15 distant metastasis, and 20 deaths. The 10-year PFS and OS were 85.4% and 90.5%, respectively. The 5 and 10-year cumulative incidence of LRR were 2.8% (95%CI: 1.4–5.2) and 4.5% (95%CI: 2.2–8.2) respectively. On univariate analysis, Basal vs. Luminal A (HR: 9.12, p<0.001) and tumor size >2cm vs. ≤2cm (HR: 4.00, p=0.022) were significant prognostic factors for LRR as first failure. On multivariate analysis, only basal subtype (HR: 6.29, p=0.011) retained significance; others effects, including luminal B/HER2 combined subtypes, were not significant. Conclusions: Long-term clinical outcomes were excellent in this cohort of breast cancer patients treated with BCT and modern systemic therapy, with 10-year LRR 4.5% and OS 90.5%. Basal subtype was an independent predictor for LRR. Conversely, HER2+ subtype was not associated with increase in LRR, in this cohort treated with BCT and trastuzumab.