Abstract P5-20-10: Patterns of use and effectiveness of neoadjuvant pertuzumab-containing regimens in stage II-III HER2-neu positive breast cancer: A retrospective, single institutional experience

Abstract

Abstract Background: Pertuzumab (P) in combination with trastuzumab (H) based chemotherapy is currently FDA- approved as a standard neoadjuvant treatment for patients with clinical stage II-III HER2-positive (HER2+) breast cancer (BC). The chemotherapy backbone of HER2-targeted therapy varies and includes a taxane (T) and/or an anthracycline coupled with cyclophosphamide (A), or carboplatin (C). The goal of this study was to retrospectively evaluate patterns of use and the pathologic complete response (pCR) rate for HP-containing regimens comparing the 3 treatment groups: A-containing, C-containing, and taxane only for stage II-III HER2+ BC. Methods: We identified all patients (n=226) with stage II-III non-inflammatory HER2+ BC who received neoadjuvant HER2-targeted therapy in combination with P and H from 2013 to 2016 through an institutional database. 48 received THP, 85 received TCHP, 5 received TCHP-A, and 88 received THP-A. All patients underwent definitive breast and lymph node surgery. Medical records were examined for patient demographics, breast cancer stage, pathology results, surgical outcomes, and treatment details. pCR was defined as ypT0/is, ypN0. Descriptive statistics and logistic regression analysis was used for statistical analysis. Results: Patient characteristics are shown in Table1. The median age was 51 (22-84) years. The pCR rates by regimen were as follows: THP (65%), TCHP (50%), THP-A (58%). After controlling for age, stage, HR status, grade, and menopausal status, THP was associated with a modestly higher pCR rate compared to TCHP or THP-A: OR = 1.82 (0.88, 3.74)(p = 0.11). Efficacy and toxicity differences will continue to be evaluated as more analytic cases become available at our institution. Conclusion: Although it is challenging to demonstrate non-inferiority without a prospective randomized trial, THP, a regimen not containing carboplatin or anthracycline, appears to have similar efficacy in selected patients with stage II-III HER2+ BC. Further research is needed to identify biomarkers to select patients appropriate for de-escalation of therapy. Table 1: Patient CharacteristicsVariable Anthracycline Containing (THP-A) N=88Carboplatin Containing (TCHP; TCHP-A*) N=90Taxane alone (THP) N=48Age at Diagnosis< 5058%52%60% > 5042%48%40%Menopausal StatusPremenopausal44%53%40% Postmenopausal56%47%60%Clinical State at DiagnosisIIA34%34%35% IIB33%32%23% IIIA12%13%23% IIIB3%3%0% IIIC18%18%19%Clinical Nodal StatusNode (+)70%70%71% Node (-)30%30%29%Nuclear Grade**II27%34%25% III73%66%75%HR statusHR(+)58%67%60% HR(-)42%33%40%*5/90 received TCHP-A; **3 patients did not have nuclear grade available; 3 patients had nuclear grade 1 cancer Citation Format: Rashmi MK, Akshara RS, Kenneth HR, Amy HZ, Bora L, Carlos BH, Mariana C-M, Elizabeth MA, Jennifer LK, Sharon GH, Alastair T, Vicente V, Debu T, Naoto UT. Patterns of use and effectiveness of neoadjuvant pertuzumab-containing regimens in stage II-III HER2-neu positive breast cancer: A retrospective, single institutional experience [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-20-10.