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

Highlights: • 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.