Evaluating the correlation between expression levels of carboxyl terminal modulator protein (CTMP) and the efficacy of trastuzumab in Syrian patients with HER2+ metastatic breast cancer.

e13008 Background: Approximately 15-20% of women diagnosed with breast cancer (BC) have HER2+ disease. Trastuzumab, the first Food and Drug Administration- approved targeted therapy for BC, serves as a turning point in the personalized therapy of HER2+ metastatic breast cancer (MBC). However, not all (HER2+MBC) patients respond to trastuzumab treatment. The attendant mechanism of trastuzumab resistance remains unclear and there are currently no conclusive biomarkers for patient response to trastuzumab. Recent studies have submitted assorted likely mechanisms leading to the resistance, including Carboxyl-terminal modulator protein (CTMP). CTMP was shown to bind to the carboxy terminus of Akt and regulate its activity. The goal of this study is to identify the role of CTMP in trastuzumab resistance in Syrian patients with (HER2+MBC). Methods: Patients received trastuzumab plus chemotherapy (either docetaxel or vinorelbine) as an adjuvant treatment until the time of disease progression. Ninety-six patients were assessable for efficacy, progressive disease (PD) and clinical benefit rate (CBR) were achieved in (32.3%) and (67.7%) respectively of the study population. Immunohistochemistry (IHC) staining was performed to examine CTMP expression in formalin-fixed paraffin-embedded (FFPE) archival tissue blocks. Results: Based on IHC scoring, 38 Cases (39.6%) had low CTMP staining, and 58 cases (60.4%) had high CTMP staining. Notably, CTMP overexpression was significantly correlated with histological grade and tumor recurrence. Moreover, the data showed that CTMP staining index is significantly higher in (PD group) than in (CBR group) (P=0.039). Intriguingly, survival analysis indicated that MBC patients with high CTMP expression had lower recurrence-free survival than those with low CTMP expression as determined by Kaplan-Meier method (p=0.048). Conclusions: Our findings confirm that (HER2+MBC) patients with high CTMP expression level tended to be refractory to trastuzumab treatment.