Second Primary Oral Squamous Cell Carcinoma After Radiotherapy: A Retrospective Cohort Study

Background：The clinical characteristics of second primary tumors in oral cavity after radiation was a special subtype of oral cancer and remained poorly studied. The purpose of the present study was to investigate the clinicopathological characteristics and prognostic factors of second primary oral squamous cell carcinoma (OSCC) after radiotherapy for head and neck cancer.Methods：The clinicopathological characteristics of 48 OSCC patients underwent radiotherapy for head and neck cancer were retrospectively analyzed by Kaplan-Meier survival analysis and Cox proportional hazards model, including gender, age, alcohol consumption, smoking, clinical stage, margin status, regional lymph node status, tumor differentiation and treatment mode.Results：The second primary OSCC mostly occurred on the tongue (18/48), bucca (12/48) and gingiva (10/48), and the 3- and 5-year overall survival (OS) was 60.3% and 39.4%, respectively. Margin status (p=0.001, log-rank=10.777) and extranodal extension (p=0.045, log-rank=4.017) were significantly associated with OS, while only margin status was found to be an independent prognostic factor of OS in the Cox proportional hazards model (p=0.003, HR=3.976).Conclusions： OSCC patients underwent radiotherapy for head and neck cancer show poor survival outcomes. Margin status is an independent prognostic factor of second primary OSCC, and the prognostic of second primary OSCC was not in accordance with sporadic OSCC.