Abstract P2-14-23: Outcome of patients with triple-negative breast cancer who did not receive adjuvant chemotherapy

Introduction Based on immunohistochemistry, triple-negative breast cancer (TNBC) lacks ER, PR and HER2, rendering them non-eligible for hormone or HER2 targeted therapy. Adjuvant chemotherapy (aCT) is often not initiated based on clinical decision making (low risk of relapse, comorbidities, older age), but sometimes because of patient refusal. We aimed to compare clinical-pathologic characteristics and outcome of patients with TNBC by reason to abstain from aCT (based on a clinical decision or patient refusal) with patients who did receive aCT. Methods In this retrospective study, we consecutively included patients with primary operable TNBC who received primary surgery, diagnosed and treated at University Hospitals Leuven between 2000-2017 (median follow-up of 9 years). The underlying reason for patients who did not receive aCT was obtained by performing a chart review: (1) by clinical decision for various different reasons: e.g. low risk of relapse (special histological subtypes e.g. adenoid cystic carcinoma, small pN0 lesions), comorbidities, older age or (2) by patient refusal. Distant disease-free survival (DDFS) and breast cancer-specific survival (BCSS) were studied endpoints. Cox proportional hazard regression models were used to estimate hazard ratios (HR) and 95% confidence intervals. All statistical tests are two-sided, a 5% significance level was assumed for all tests. Analyses have been performed using SAS software (version 9.4 of the SAS System for Windows). Results We included 673 patients with TNBC of whom 163 (24.2%) did not receive aCT; 141 (20.9%) due to a clinical decision, and 22 (3.3%) due to patient refusal. Mean age at diagnosis was 71.6 years and 68.7 years, respectively, compared to 52.3 years for those who received aCT. Patients who received aCT showed a tendency towards better DDFS when compared to the group of patients who refused aCT (HR=0.621 [0.217;1.774]; p=0.37), and when compared to the group who did not receive aCT due to a clinical decision (HR=0.545 [0.294;1.009]; p=0.05). The group of patients who did not receive aCT due to a clinical decision showed a tendency towards worse DDFS compared to the group of patients who refused aCT (HR=1.140 [0.390;3.30]; p=0.81), however this difference was not statistically significant. Interestingly, BCSS for patients who received aCT was better compared to patients who did not receive aCT due to a clinical decision (HR=0.484 [0.250;0.935]; p=0.03) and showed a tendency towards better survival when compared to the group of patients who refused aCT (HR= 0.582 [0.174;1.946]; p=0.38). Patients who did not receive aCT due to a clinical decision showed a tendency towards worse BCSS than patients refusing therapy (HR=1.204 [0.353;4.089]; p=0.77). Conclusion In this cohort, TNBC patients treated with primary surgery who refused aCT appeared to have worse DDFS and BCSS compared to patients who received aCT. Patients who did not receive aCT due to a clinical decision hade worse BCSS and a tendency towards worse DDFS, compared to patients who received aCT. These results suggest that chemotherapy is effective in reducing cancer-related mortality. Citation Format: Hava Izci, Jan Ardui, Annouschka Laenen, Freija Verdoodt, Giuseppe Floris, Laurence Slembrouck, Ignace Vergote, Ann Smeets, Els Van Nieuwenhuysen, Sileny Han, Ines Nevelsteen, Caroline Weltens, Patrick Berteloot, Kevin Punie, Hans Wildiers, Patrick Neven. Outcome of patients with triple-negative breast cancer who did not receive adjuvant chemotherapy [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-14-23.