At 62 months, cyclooxygenase-2 staining had a sensitivity and specificity for recurrence of 81%.
Expression of cyclooxygenase-2 (COX-2) in prostate cancer tissue is an independent predictor of biochemical recurrence following radical prostatectomy.
COX-2 is an inducible proinflammatory enzyme that catalyzes conversion of arachidonic acid into physiologically active eicosanoids such as prostaglandin and thromboxane. COX-2 has been implicated in prostate carcinogenesis, but its role in cancer progression is less clear.
Brian L. Cohen, MD, of the University of Miami, and his colleagues determined COX-2 expression using immunohistochemical analysis. This involved using anti-COX-2 antibodies in archival prostate cancer specimens obtained from 60 patients who underwent radical prostatectomy and did not receive neoadjuvant hormonal therapy.
The patients were followed for a minimum of 62 months (mean, 95 months). Twenty-three had biochemical or clinical recurrence during follow-up (mean time to recurrence, 38.2 months) and 37 remained disease-free. The investigators ob-served COX-2 expression in prostate cancer cells, in adjacent normal glands, and in specimens from patients who experienced disease progression.
The researchers observed low-grade staining in normal-benign tissue not adjacent to prostate cancer cells, regardless of whether the specimen was obtained from a patient with or without recurrence. High-grade staining was observed, however, in normal-benign tissue adjacent to tumor cells obtained from patients who had recurrence but not from those without recurrence, suggesting that normal prostate epithelial cells may express COX-2 if they are adjacent to prostate cancer cells that have malignant potential.
COX-2 staining predicted recurrence with a sensitivity of 81% at 62 months, 84% at 72 months, 86.7% at 100 months, and 82.6% at 121 months. The specificity of COX-2 staining for recurrence was 81% at 62 months, 84% at 72 months, and 86.7% at 100 months. The positive predictive value of COX-2 staining increased significantly from 63.6% at 62 months to 90.5% at 100 months, and the negative predictive value decreased from 92.1% at 62 months to 81.3% at 100 months.
“COX-2 expression in prostate cancer correlates with aggressive disease and is an independent prognostic indicator of biochemical recurrence,” the authors wrote in the International Journal of Cancer (2006;119:1082-1087).
“The high sensitivity, specificity, and positive predictive value of COX-2 expression point to the possibility that future treatment should consider inhibition of inflammatory pathways either at the time of initial treatment or together with androgen ablation during the treatment of residual disease.”