Synchronous malignancies in patients with squamous cell carcinomas of the oral cavity

Purpose: Synchronous malignancies in patients with squamous cell carcinomas of the oral cavity (OCSCC) are occasionally encountered. In the current study we tried to evaluate their frequency, detectability by ¹⁸F- fluorodeoxyglucose (FDG) studies, and prognostic factors. Methods: A retrospective analysis of patients with primary OCSCC enrolled for ¹⁸F-FDG studies from 2002 to 2008 was performed. The detectability of synchronous second cancers by ¹⁸F-FDG studies was defined by the scoring of two interpreters. Prognostic factors for overall survival in patients receiving curative-intent treatment were assessed using the univariate Kaplan-Mayer analysis and the multivariate Cox regression model. Results: Of 764 patients, 40 (5.2%) had synchronous malignancies. ¹⁸F-FDG studies detected 22 (48%) of 46 synchronous second cancers. For synchronous cancers at the hypopharynx, esophagus, or liver, the median survival of patients was no longer than 1 year, and the detection rates by ¹⁸F-FDG studies were 100, 86, and 25%, respectively. In the 33 patients receiving curative-intent treatment, the site of second cancer, complete surgical resection of all known tumors, and the oral habit of betel quid/areca nut chewing are significant prognostic factors in the univariate analysis, while the site of second cancer is the only significant prognostic factor in the multivariate analysis (p=0.041). Conclusion: The site of second cancer is the most significant prognostic factor in OCSCC patients with synchronous malignancies receiving curative-intent treatment. ¹⁸F-FDG studies detect synchronous malignancies with poor prognosis in OCSCC patients except for hepatic cancers. In OCSCC patients with synchronous malignancies with poor prognosis, prospective studies comparing different treatment options should be further conducted.