The prognostic value of COX-2 expression on circulating tumor cells in nasopharyngeal carcinoma: A prospective analysis

•COX-2 was expressed in a subset of CTCs in NPC patients, and the expression status evolved from baseline (87/131, 66.4%) to the end of concurrent radiochemotherapy (53/115, 46.1%).•Post-therapeutic COX-2 expression on CTCs remained an independent prognostic indicator for poorer progression-free survival (HR 2.17, P = 0.019) and overall survival (HR 2.41, P = 0.024) in NPC patients.•NPC patients with post-therapeutic COX-2 expression on CTCs had significantly poorer treatment response (P = 0.011) and higher risk of tumor relapse (P = 0.026) and metastasis (P = 0.007). The prognostic significance of circulating tumor cells (CTCs) in head and neck cancer is still under debate, as only a few studies have been reported and limited conclusions are reached. Besides, CTCs’ count alone was utilized as an indicator in the previous researches. As a form of ‘liquid biopsy’, the further identification of genetic or phenotypic biomarkers on CTCs could possibly provide further clinical significance. The prospective study enrolled 131 patients with nasopharyngeal carcinoma (NPC). CTCs were isolated at baseline and at the end of concurrent chemoradiotherapy, and cyclooxygenase-2 (COX-2) expression status of CTCs was detected by RNA-in situ hybridization (ISH) method. Results were correlated with patient’s clinicopathological parameters and treatment outcomes. Univariate and multivariate survival analyses were performed to determine the prognostic significance. COX-2 expression was found in 87/131 (66.4%) patients at baseline and 53/115 (46.1%) patients at the end of concurrent chemoradiotherapy. Patients with post-therapeutic COX-2 expression had significantly poorer treatment response (P = 0.011) and higher risk of tumor relapse (P = 0.026) and metastasis (P = 0.007). Besides, multivariate analysis revealed that post-therapeutic COX-2 expression on CTCs remained an independent prognostic indicator for poorer progression-free survival (HR 2.17, P = 0.019) and overall survival (HR 2.41, P = 0.024). The study demonstrated that post-therapeutic COX-2 expression on CTCs was a novel and promising prognostic indicator for NPC patients. Future studies are needed to validate our findings and further clarify the value of integrating the indicator with current clinical strategies in improving survival of NPC patients.