Cyclo-oxygenase-2 over-expression in sporadic colorectal carcinoma without lymph node involvement

Background: Cyclo-oxygenase-2 over-expression has been reported in most advanced human colorectal cancers. Aims: To assess the prevalence of cyclo-oxygenase-2 over-expression in non-advanced colorectal cancers, to investigate the correlation between cyclo-oxygenase-2 status and tumour clinicopathological features and molecular phenotype, and to determine the impact of cyclo-oxygenase-2 status on long-term clinical outcome. Methods: Sixty-one patients who had undergone surgery for colorectal cancer without lymph node involvement were evaluated retrospectively. Cyclo-oxygenase-2 expression was determined by immunohistochemistry. The tumour replication error phenotype was assessed by amplification of the two microsatellites, BAT-25 and BAT-26. Results: Thirty-six tumours were classified as cyclo-oxygenase-2 positive and 25 as cyclo-oxygenase-2 negative. No correlation was found between cyclo-oxygenase2 over-expression and clinicopathological features or molecular phenotype. Cyclo-oxygenase-2 over-expression was an independent predictor of a poor prognosis. Indeed, the relative risk of tumour recurrence or death for patients with cyclo-oxygenase-2- positive tumours was 2.13 times that of patients with cyclo-oxygenase-2- negative tumours (P = 0.008; 95% confidence interval, 1.22-3.73). This difference remained significant when post-operative deaths were censored in the multivariate analysis (P = 0.014). Conclusion: Cyclo-oxygenase-2 over-expression is not associated with tumour phenotype, but is indicative of a poorer clinical outcome in patients with non-advanced colorectal carcinoma.