Evaluation Of Circulating Tumor Cells (Ctcs) As A Potential Biomarker In Patients With Colorectal Cancer (Crc): A Prospective Analysis

e22016 Background: CRC is the third most prevalent cancer worldwide. New prognostic markers are needed to identify patients with worse prognosis and to aid the development of more effective therapeutic regimens. Circulating tumor cells have emerged as a possible tool to predict outcome in some malignances. The aim of this study was to analyzed the interaction between some clinical and laboratories variables with CTCs levels. We also analyzed the interference of previous exposure to bevacizumab in CTCs in metastatic CRC patients. Methods: Metastatic and non-metastatic CRC patients treated in a single tertiary institution from Brazil were sequentially recruited. Written informed consent was obtained from all patients. Blood samples were collected before the beginning of first chemotherapy cycle and every two months. The isolation, characterization and counting of CTCs were made by ISET (Isolation by Size of Epithelial Tumor Cells; Rarecells Diagnostics, Paris, France). Results: Fifty four patients were included. The median age was 59 years (30-81 years). Twenty three patients were women (42.6%) and 31 were men (57.4%). At the time of enrollment, 46 patients had stage IV disease (85.2%) and liver was the most common site of metastasis (22.2%). We used the pre-established cut-off of 0.3 CTC/ml. No correlation between CEA and CTCs levels was found in the general population (p=0.606), accordingly with previous published data. In the metastatic setting, median time to progression (mTTP) was 9.1 months and was not correlated with CTCs. CTCs counts correlated inversely with disease stage, a smaller number of CTCs was found in more advanced stages (p=0.033). The majority of our metastatic patients (60.8%) were exposed to bevacizumab combined with chemotherapy. Thus, a possible explanation for the inverse correlation between CTCs and disease stage is that bevacizumab could prevent the release of CTCs by tumor, probably by changes in tumor angiogenesis. Conclusions: CTCs did not correlate with CEA neither TTP but were inversely correlated with disease stage in our cohort. The interaction between bevacizumab exposure and CTCs level should be investigated in further studies.