Second primary cancers in patients with oral cavity cancer included in the Korea Central Cancer Registry.

OBJECTIVES: The improved survival of patients with oral cavity cancer (OCC) has generated interest in factors affecting survivorship, particularly among second primary cancer (SPC) patients. This study aimed to assess the incidence, patterns, and risk factors for SPC after OCC treatment in the Korean population. MATERIALS AND METHODS: Data from 15,261 patients with OCC (ICD-O: C01-C06) identified between 1993 and 2014 were extracted from the Korean Central Cancer Registry. The standardized incidence ratio (SIR) for SPC after index OCC was calculated, and Poisson regression analysis was performed to evaluate the risk factors for SPC among survivors. RESULTS: The overall SIR for SPC among OCC survivors was 1.47 (95% confidence interval [CI] 1.39-1.56). SIR differed by sex (male: 1.51 vs. female: 1.37), age at diagnosis (<45 years: 2.47 vs. 45-64 years: 1.68 vs. >/= 65 years: 1.10), index OCC subsite (floor of mouth: 1.95 vs. gum: 1.30), follow-up duration (6-23 months: 1.64 vs. 24-59 months: 1.51 vs. 60-119 months: 1.48 vs. >/= 120 months: 1.24), histological OCC type (salivary gland malignancy: 1.77 vs. squamous cell carcinoma: 1.44 vs. others: 1.47), and radiation history (any: 1.94 vs. no radiation: 1.37). The risk factors for SPC development among OCC survivors included younger age at diagnosis and history of radiation therapy. CONCLUSION: OCC survivors have significantly increased risks of SPCs, exhibiting distinctive site distributions and chronological patterns. These patients would benefit from an SPC surveillance protocol.