524PD - ERCC1, Defective Mismatch Repair Status as Predictive Biomarker of Survival for Stage III Colon Cancer Patients Receiving Oxaliplatin Based Adjuvant Chemotherapy

Abstract

ABSTRACT Background Several trials showed excision repair cross-complementation group 1 (ERCC1) expression status is a candidate marker for predicting efficacy of oxaliplatin (OX) treatment for metastatic colorectal cancer (CRC). Association between the expression of mismatch repair genes (MMR) and favorable postoperative survival in stage II CRC receiving 5-FU chemotherapy has been identified. whether the expression of ERCC1 protein and MMR status are associated with survival of stage IIIB colon cancer receiving OX-based chemotherapy is unclear. Patients and methods We enrolled 255 patients with stage III colon cancer after radical surgery. There were 95 patients receiving full-course Mayo clinic chemotherapy and 160 patients received mFOLFOX6 or XELOX chemotherapy. Immunohistochemistry analysis of the expression of MMR and ERCC1 was performed in tumor tissue. A predictive model for 5-year disease-free survival (DFS) and overall survival (OS) was constructed by using Kaplan-Meier analysis, logistic and Cox regression. Results The patients with positive ERCC1 tumors had lower 5-year DFS (54%) than those with negative ERCC1 tumors (72%) in combined therapy group (HR: 1.98 95%CI: 1.19-3.31 p = 0.009).The OS was also lower in combined therapy group with positive ERCC1 tumors (60%) than those patients with negative ERCC1 tumors (78% HR: 2.44 95%CI: 1.37-4.34 p = 0.02). In multivariate analysis, ERCC1 expression remained an independent significant predictive factor for DFS and OS (DFS HR: 2.33 95%CI: 1.37-3.93 p Conclusion ERCC1 status was shown to be a highly predictive selection criterion in relation to the treatment decision regarding the addition of OX to 5-FU for stage IIIB colon cancer. MMR status had no predictive value in this setting. Disclosure All authors have declared no conflicts of interest.