Purpose: An increasing attention has turned to the burden of secondary malignant neoplasms (SMNs) in long-term cancer survivors. The aim of this study was to describe the incidence, and survival outcomes of SMNs in primary hypopharyngeal squamous cell carcinoma (HSCC). Materials and Methods: Patients with primary diagnosis with HSCC and reported to the Surveillance, Epidemiology, and End Results (SEER) program between 1973 and 2016 were eligible for this study. Kaplan-Meier method was used to estimate the cumulative incidence of SMNs and survival rates. Standardized incidence ratios (SIRs) of SMNs after primary HSCC were also assessed. Results: A total of 8518 patients diagnosed with HSCC as their first malignancy were included (median follow-up: 142 months). 984 patients developed SMNs with a median time from primary diagnosis to an SMN diagnosis was 3.8 years. The cumulative incidences of any SMNs were 30% at 10 years, and 54% at 20 years. The top three common secondary tumors were lung, esophageal and oral cavity cancer, with cumulative incidence rates of 22%, 12% and 9% at 20 years, irrespectively. The SIR for SMNs in survivors of HSCC compared with the general population was 2.86 and 5-year overall survival (OS) rate after SMNS was 16%. Esophageal carcinoma as a SMN showed the highest SIR of 23.81 and presented with the lowest 5-year OS rate of 7%. Conclusions: Survivors of HSCC are at increased risks of developing SMNs compared with the baseline population. Patients developed oesophageal carcinoma as SMNs showed the highest SIR and shortest survival

Keywords: Second primary malignancy, Hypopharyngeal cancer, Cumulative incidence, Survival, Risk factor