Clinical study of multiple primary and double cancers including oral squamous cell carcinoma

Abstract Objective In recent years, there has been an increase in the incidence of multiple and double cancers involving the oral cavity. In this study, we clinically reviewed patients with multiple or double cancers. Patients and methods The subjects were 696 patients with multiple oral squamous cell carcinomas who had visited the Department of Oral and Maxillofacial Surgery, Tokyo Dental College during the 26-year period between 1982 and 2008 and 497 patients with double cancers treated during the 16-year period from 1992, when endoscopy was started, to 2008. Results The incidence of multiple primary cancers was 26 (3.7%) in 696 patients. The most common primary site of multiple cancers was the mandibular gingiva (42.3%). The maximum number of multiple cancers per patient was seven. On the other hand, the incidence of double cancers was 43 (8.7%) in 497 patients, with esophageal cancer being the most frequent (58.1%). The most common primary site of oral cancers in double cancer patients was the oral floor (32.6%). Conclusions About 10% of all patients developed double cancers. Therefore, follow-up is necessary not only for recurrence and metastasis, but also for the development of a primary cancer elsewhere through strengthening endoscopy in close cooperation with the endoscopist.