Tissue Microarray Analysis Reveals Prognostic Significance of COX‐2 Expression for Local Relapse in T1–2N0 Larynx Cancer Treated with Primary Radiation Therapy

Abstract

The purpose of this analysis is to determine whether a significant correlation exists between cyclooxygenase-2 (COX-2) expression and local relapse in a large cohort of patients with T1 to 2N0 laryngeal cancer treated with primary radiation therapy. Clinical and molecular analyses were conducted on 123 patients with biopsy-proven T1 to 2N0 laryngeal cancer. Clinical prognostic factors included pretreatment hemoglobin, age, sex, race, T stage, tumor subsite, beam energy, biologically equivalent dose, therapy duration, and treatment date. Molecular prognostic factors included COX-2, p53, and Ki-67 expression. Expression levels were determined by immunohistochemistry on paraffin-embedded tissues arrayed on tissue microarrays. Multivariate analysis was done with the Cox proportional hazards model. Thirty-two patients have locally relapsed, for an actuarial 5-year local relapse-free rate of 70.4%. On multivariate analysis, positive COX-2 expression predicted local relapse after radiation therapy. The relative risk (RR) for local relapse with COX-2 positivity was 2.57 (95% CI, 1.21-5.47; P = .01). Other prognostic factors for local relapse included negative Ki-67 expression (RR = 5.72; 95% CI, 2.04-16.1; P < .001), T2 stage (RR = 2.98; 95% CI, 1.39-6.38; P = .005), and therapy duration greater than 43 days (RR = 6.04; 95% CI, 1.37-26.7; P = .02). Positive COX-2 expression predicts for local relapse in T1 to 2N0 larynx cancer in a multivariate model. This relationship may have potential therapeutic implications regarding the use of COX-2 inhibitors during radiation therapy for optimal outcome.