Abstract P1-07-24: Evaluation of the prognostic value of all four HER family receptors in patients with metastatic breast cancer treated with trastuzumab: A hellenic cooperative oncology group (HeCOG) study

Abstract

Abstract Background-aim: Metastatic breast cancer (MBC) is an incurable disease. Trastuzumab, a recombinant humanized monoclonal antibody, was found to significantly prolongsurvival of patients with metastatic HER2 over-expressing and/or amplified breast cancer. In the current study, we performed a complete analysis, with four different methods, of all four HER family receptors, in a series of patients with metastatic breast cancer treated with trastuzumab-based regimens and evaluated their prognostic value. Methods: Formalin-fixed paraffin-embedded tumor tissue samples were collected from 227 patients, considered to be HER2-positive when assessed at the local laboratories. We evaluated gene amplification, copy number variations (CNVs), transcriptional profiling and protein expression of all four HER family members. In addition, our analysis included the evaluation of several other factors by immunohistochemistry (IHC), such as pHER2Tyr1221/1222, pHER2Tyr877 and PTEN. Results: Central review of HER2 status by IHC and fluorescence in situ hybridization revealed that of the 227 patients, only 139 (61.2%) were truly HER2-positive. Regarding the 191 patients treated with trastuzumab as first-line therapy, median time to progression (TTP) was 15.3 months and 10.4 months for HER2-positive and HER2-negative participants, respectively. Median survival was 50.4 months for HER2-positive and 38.1 months for HER2-negative patients. In HER2-positive patients, high HER3 mRNA expression was of favorable prognostic significance for TTP and survival (HR=0.43, 95% CI 0.21-0.88, Wald's p=0.022 and HR=0.43, 95% CI 0.21-0.88, p=0.021, respectively), while EGFR copy gain and EGFR protein expression were associated with higher risk for disease progression in HER2-negative patients (HR=3.53, 95% CI 1.19-10.50, p=0.023 and HR=3.37, 95% CI 1.12-10.17, p=0.031, respectively). Positive HER3 protein expression was a favorable factor for TTP in HER2-negative patients (HR=0.43, 95% CI 0.22-0.84, p=0.014). In the multivariate analysis, only EGFR copy gain retained its prognostic significance for TTP in the HER2-negative population (HR=4.81, 95% CI 1.52-15.82, p=0.008), while none of the examined factorsretained their prognostic significance for TTP or survival in the HER2-positive subgroup. Conclusions: The present study suggests that EGFR copy gain represents a negative prognostic factor for TTP in HER2-negative patients with metastatic breast cancer. In addition, high HER3 mRNA expression appears to be of favorable prognostic significance for TTP and survival in HER2-positive patients. Given the small number of patients included in the current analysis and the retrospective nature of the study, our findings should be validated in larger cohorts. Citation Format: Koutras A, Kotoula V, Koliou G-A, Kouvatseas G, Christodoulou C, Pectasides D, Batistatou A, Bobos M, Tsolaki E, Papadopoulou K, Pentheroudakis G, Papakostas P, Pervana S, Petraki K, Chrisafi S, Razis E, Psyrri A, Bafaloukos D, Kalogeras KT, Kalofonos HP, Fountzilas G. Evaluation of the prognostic value of all four HER family receptors in patients with metastatic breast cancer treated with trastuzumab: A hellenic cooperative oncology group (HeCOG) study [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 P1-07-24.