Clinicopathologic significance of cyclooxygenase-2 overexpression in colorectal adenocarcinoma

Background and aim: Cyclooxygenase-2 (COX-2) plays an important role in colorectal cancer development and is frequently up-regulated in colorectal cancer. The purpose of this study was to investigate COX-2 overexpression in colorectal adenocarcinoma and to evaluate the correlation with the clinicopathological parameters and p53 expression, as well as its effect on patient survival. Methods: We evaluated the expression of COX-2 and p53 on the tissue microarray of 414 colorectal adenocarcinomas by immunohistochemistry. Data was analyzed by Fisher's exact test, χ²-test, one-way ANOVA, Cox regression hazards model and log-rank test with Kaplan–Meier curves. Results: The cytoplasmic COX-2 overexpression was detected in 56.3% of colorectal adenocarcinoma samples. COX-2 overexpression was correlated with favorable clinicopathologic factors in lymph node metastasis (P= 0.002), American Joint Committee on Cancer and Dukes’ stage (P= 0.008 and P= 0.017, respectively), and lymphatic invasion (P= 0.001). Other characteristics associated with COX-2 overexpression were colonic site of tumor (P= 0.008) and poor differentiation (P= 0.017). There was no correlation between COX-2 overexpression and p53 expression (P= 0.485). In univariate survival analysis, patients with COX-2 overexpression revealed better overall survival and disease-free survival (P= 0.021 and P= 0.017, respectively, log-rank test). In multivariate survival analysis with the Cox proportional hazards model, COX-2 overexpression was an independent prognostic factor of overall survival and disease-free survival (P= 0.029 and P= 0.039, respectively). Conclusions: COX-2 overexpression was significantly associated with favorable clinicopathologic phenotype and an indicator of better survival in our cohort of colorectal cancer patients.