Synchronous and metachronous cancers in patients with gastric cancer.

Background and Objectives: The purpose of this study is to investigate characteristics of synchronous and metachronous cancer in gastric cancer and to suggest appropriate methods of treatment management.
Methods: We reviewed 4,593 patients who underwent operations for gastric cancer at Seoul National University Hospital from 1999 to 2005. We selected those patients who had also been diagnosed with another primary cancer and classified patients into three groups according to the date of detection of another primary cancer. We analyzed their clinicopathological features.
Results: The incidence of synchronous or metachronous cancer in addition to gastric cancer was 3.4%. The most common another primary cancer was colorectal cancer (20.1%), followed by lung cancer and liver cancer. The majority of synchronous cancers were operated on at the same time as gastric cancer. Eighty-five percent of the synchronous group and 45% of the post-metachronous group were detected by a routine checkup, without prior symptoms. There was no postoperative mortality and the overall 5-year survival rate was 69.4%.
Conclusion: Synchronous cancer should be considered in the preoperative workup and combined resection should be applied whenever possible. Periodic examination for metachronous cancer is necessary during the postoperative period.