抄録
It is reported that patients with oral squamous cell carcinoma （OSCC） frequently suffer multiple primary cancers more than those with other types of malignancy, therefore early detection is important for the successful treatment of oral cancers. We retrospectively analyzed 518 patients with oral squamous cell carcinoma who presented to the Oral Cancer Center of Tokyo Dental College between April 2007 and March 2016 to clinically analyze and investigate the characteristics and prognosis of 48 patients with multiple primary cancers. The incidence of multiple primary cancers in patients with OSCC was 9.3％ and the most frequent location of occurrence was the esophagus （25.0％）, and there were early stage cancers. Oral primary cancers in the floor of the mouth accounted for 32.3％. 62.5％ of synchronous and 78.1％ of metachronous cancers were detected by gastrointestinal endoscopy and contrast CT. There was no significant difference in the 5-year overall survival rate for multiple primary cancers compared with single primary cancers. On the other hand, patients with multiple lung cancer had a significantly lower overall survival rate （log-rank P＜0.01）. In conclusion, early detection by preoperative screening and treatment are important for the long-term survival of patients with multiple primary cancers.
