The Presence Of Tyms Immunostaining In Circulating Tumor Cells Is A Predictive Biomarker In Colorectal Cancer

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Background: colorectal cancer (CRC) was the third most commonly diagnosed cancer in both men and women in the last three years in the United States (Siegel et al., 2011, 2012, 2013). The first strategy for treatment is complete resection of the lesion. However, some patients experience recurrence, believed to be due to residual resistant micrometastases. Circulating tumor cells (CTCs) have been considered an important prognostic biomarker and crucial for tumor dissemination. Traditional diagnostic methods are unable to detect CTCs present in these sites and released into the circulation. Objective: to count CTCs levels and search for Thymidylate synthase (TYMS), a drug resistance gene, in these cells from patients with metastatic or advanced colorectal cancer. Methods: prospective study made by blood collection of patients with metastatic or advanced CRC. Blood was collected before the beginning of chemotherapy and after 60 days, in accordance with image exams. The sample was filtered on ISET (Isolation by Size of Epithelial Tumor Cells) according to manufacture procedure. CTCs fixed on spots from ISET membranes were stained by immunocytochemistry with anti-TYMS antibody and counterstained with hematoxylin-eosyn. Leucocytes were identified by anti-CD45 antibody. CTCs were analised by light microscope and quantified by 1 mL of blood. Results: there were included 42 patients. 78.5% were treated with FOLFOX or FOLFORI. The median age was 58 years-old (30-81). The majority of patients was men (59.5%) and included at stage IV of disease (88%). The median CTCs numbers detected in all patients were 2.18 CTCs/ml (0- 31.25) at baseline. Immunostaining in CTCs with TYMS was performed in 41 samples. Nine (21.9%) were found positive. Six of these patients had tumor progression in a follow-up of 12 months after treatment with 5-FU. Among patients with CTC TYMS positive and disease progression, 4 had also tumor tissue positive. Conclusion: It is been related in literature that high tissue expression of TYMS shows worse response to 5-FU-based chemotherapy (Lurje et al., 2009). Our results with CTCs expressing TYMS strongly contribute with these findings and suggest that maybe these cells can be used as a predictor biomarker of chemotherapy response. Furthermore, CTCs levels may offer a novel approach to follow up patients in an individualized manner. Citation Format: Ludmilla T. Chinen, Emne Ali Abdallah, Virgilio S. Silva, Marcilei E. Buim, Marcelo Calil Neto, Jose Luiz Gasparini Junior, Bruna Maria Malagoli Rocha, Juliana R. Romero, Natalia Breve Mingues, Fernando Augusto Soares, Mitzi Brentani, Marcello Ferretti Fanelli. The presence of TYMS immunostaining in circulating tumor cells is a predictive biomarker in colorectal cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-194. doi:10.1158/1538-7445.AM2014-LB-194