ERCC1, defective mismatch repair status as predictive biomarkers of survival for stage III colon cancer patients receiving oxaliplatin-based adjuvant chemotherapy

Background: Excision repair cross-complementation group 1 (ERCC1) expression status has been identified as a candidate marker for predicting efficacy of oxaliplatin (OX) treatment for metastatic colorectal cancer (CRC) in several trials. Also, an association between expression of mismatch repair (MMR) genes and favourable postoperative survival in stage II CRC receiving 5-FU chemotherapy has been identified. It is unknown if the expression of ERCC1 protein and MMR status are associated with survival of stage III colon cancer receiving OX-based chemotherapy. Methods: Immunohistochemistry (IHC) analysis of the expression of MMR and ERCC1 was performed on tumour tissue of 255 patients with stage III colon cancer. In all, 95 patients received fluoropyrimidine-based chemotherapy and 160 patients received OX-based chemotherapy. A predictive model for 5-year disease-free survival (DFS) and overall survival (OS) was constructed using Kaplan-Meier analysis, logistic and Cox regression. Results: Patients who were treated with OX-based therapy with positive ERCC1 tumours had lower 5-year DFS (54%) and OS (60%) than those with negative ERCC1 tumours (72% and 78%, respectively; DFS HR: 1.98, 95% confidence interval (CI): 1.19-3.31, P = 0.009; OS HR: 2.44, 95% CI: 1.37-4.34, P = 0.02). Excision repair cross-complementation group 1 status did not impact DFS or OS in fluorouracil group (DFS HR: 1.16, 95% CI: 0.63-2.14, P = 0.62; OS HR: 1.16, 95% CI: 0.63-2.14, P = 0.63), whereas MMR status had no impact on DFS or OS in either group. Conclusion: Excision repair cross-complementation group 1 status is highly predictive of which patients will benefit from the addition of OX to 5-FU for stage III colon cancer. Mismatch repair status had no predictive value in this setting.