Objective: The ability to predict which men will experience biochemical recurrence (BCR) after salvage radiation therapy (SRT) for recurrent prostate cancer following radical prostatectomy has potential for improvement. Cyclooxygenase-2 (COX-2) overexpression has previously correlated with poor clinical outcomes following primary treatment for prostate cancer, however its predictive ability in the specific setting of SRT has not been examined to date. This study evaluated the association between COX-2 staining intensity and BCR following SRT for recurrent prostate cancer.
Methods: We utilized a cohort of 151 patients who underwent SRT between July 1987 and July 2003. COX-2 staining intensity in primary tumor samples was detected using monoclonal antibodies and quantified using a computer-assisted method. The association between COX-2 staining intensity and BCR was evaluated using multivariable Cox regression models.
Results: When examining COX-2 staining level as three-level categorical variable (low, moderate, high) based on approximate sample tertiles, there was no evidence of an association with BCR (P=0.18). More specifically, in comparison to patients with low staining intensity, there was no significant difference in risk of BCR for moderate (Relative risk [RR]: 1.17, P=0.56) or high (RR: 0.72, P=0.22) COX-2 staining intensity patients. This lack of association was also observed when considering COX-2 staining intensity as a continuous variable (RR: 0.83, P=0.15).
Conclusion: Our results indicate that COX-2 staining intensity is likely of little use in discriminating prognosis of SRT. It appears that the search for prognostic factors associated with BCR should continue elsewhere in order to further enhance patient selection for SRT.
Keywords: biochemical recurrence; prostate cancer; salvage radiation therapy; tumor biomarker.