The role of cyclooxygenase 2 expression in stage II and stage III colon cancer survival.

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Introduction

An association between overexpression of cyclooxgenase 2 (COX-2) and poor prognosis has been demonstrated in some but not all colon cancer observational studies. This study examines the role of COX-2 expression and survival in a population-based cohort of patients with stage II and III colon cancer.

Methods

Immunohistochemical expression of COX-2 (positive vs. negative) was assessed in tissue microarrays using digital immunoscoring from 665 stage II and III colon cancer patients undergoing surgical resection in the Belfast and South Eastern Health and Social Care Trusts (2004-2008). Five-year follow-up data were obtained through the Northern Ireland Cancer Registry. Cox proportional hazards models were used to calculate hazard ratios (HR) and 95% confidence intervals (CI) for colon cancer-specific survival (CSS) and overall survival (OS).

Results

Medication history was available for n=545 (82.0%) patients and aspirin use within this subgroup was n=110 (20.2%). COX-2 positive cancers (p=0.02) and aspirin users (p=0.002) were slightly older but stage distribution was similar for these variables. COX-2 expression and aspirin use were not associated with improved CSS or OS after adjusting for age, gender and stage. CSS was improved amongst aspirin users with COX-2 positive tumours (HR 0.48, CI 0.25-0.95) but this finding was no longer statistically significant when adjuvant chemotherapy and co-morbidities were considered (HR 0.54, CI 0.26-1.12). Similar results were obtained for OS.

Conclusion

COX-2 expression does not appear to have prognostic or predictive potential within this population-based cohort of colon cancer.