Prognostic value of COX‐2 immunohistochemical expression evaluated by quantitative image analysis in colorectal cancer

Epidemiological studies have shown that the inducible form of cyclooxygenase (COX‐2) may be involved in colorectal carcinogenesis, but it is controversial whether its expression is a prognostic factor for colorectal cancer. The aim of the study was to examine the expression of COX‐2 in colorectal cancer and investigate its prognostic relevance. Tissue sections of primary tumors from 132 patients undergoing curative resection for colorectal cancer were immunohistochemically examined for COX‐2 expression. The levels of intensity and extent of COX‐2 staining were quantified by use of a computerized image analysis system and correlated with various clinicopathological characteristics and survival. COX‐2 immunoreactivity was observed in the cytoplasm of tumour epithelial cells of all colorectal cancer tissues examined. No significant correlation was found between levels of intensity and extent of COX‐2 staining and various clinicopathological characteristics, including age, gender, tumor location, tumor size, tumor grade, depth of invasion, lymph node status and TNM stage. There was an inverse correlation between intensity and extent of COX‐2 staining scores (Spearman's rho=?0.414; p<0.001). To analyze the prognostic value of intensity and extent of COX‐2 staining, the patients were divided into four groups with respect to quartiles (≤25; >25 to ≤50; >50 to ≤75; and >75). No significant disease‐specific survival difference among the quartiles was found based on analysis of intensity (p=0.689) and extent (p=0.975) of COX‐2 staining. These results suggest that the expression of COX‐2 protein has no significant impact on the outcome of patients with colorectal cancer.