The effect of histological subtypes on survival outcome in nasopharyngeal carcinoma after extensive follow up

Abstract

Background: No consensus exists regarding the follow-up of nasopharyngeal carcinoma (NPC) patients stratified by different histological subtypes. The purpose of this study was to determine the hazard function of disease-related death and assess the prognostic effect of early and late disease-related death in NPC according to histological subtypes. Methods: We included non-metastatic NPC patients between 2004 and 2014 using the Surveillance, Epidemiology and End-Results (SEER) program. Life-table methods, Kaplan-Meier methods, and a multivariate Cox regression model were used in the analysis. Results: We identified 2,845 patients in this study including 1,218 (42.8%), 849 (29.8%), and 778 (27.3%) patients with keratinizing squamous cell carcinoma (KSCC), differentiated non-keratinizing carcinoma (DNKC), and undifferentiated non-keratinizing carcinoma (UNKC), respectively. Most NPC-related death (89.8%) occurred within 5 years of diagnosis. In the entire cohort, the hazard curve for NPC-related death peaked at 2 years. It peaked at 1 year, 2- and 5-year, and 2- and 6-year in patients with KSCC, DNKC, and UNKC, respectively. Within the follow-up period over 5 years, patients with DNKC had poorer NPC- specific survival (NPC-SS) compared to UNKC, and had comparable NPC-SS between the two subtypes after more than 5 years of follow-up. Moreover, within the follow-up period of 1, 2, and 3 years, patients with KSCC experienced poorer NPC-SS compared to UNKC but there was comparable NPC-SS between KSCC and UNKC patients after more than 3 years of follow-up. Conclusions: The hazard rate patterns for NPC-related mortality significantly differed between histological subtypes. Tailored surveillance and follow-up strategies should be designed in NPC patients according to histological subtypes.