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Metachronous Double Primary Gastric and Colorectal Cancer: Is Prognosis Better with Gastric or Colorectal Cancer Occurring First?

The purpose of this study was to investigate the clinicopathological features of gastric precedence (GP) and colorectal precedence (CP) metachronous double primary gastric and colorectal cancer (MDPGCC) and determine the biological significance of these two types of malignancy in making a prognosis. Between January 1990 and December 2009, 4523 patients underwent surgical treatment or chemotherapy, but no endoscopic resection for gastric or colorectal cancer. From this group, we selected those patients in whom another gastric or colorectal primary cancer developing from another origin had been diagnosed. For classification as MDPGCC there had to be an interval of 6 months or more before a secondary diagnosis of gastric or colorectal cancer. Among 4523 patients treated for gastric or colorectal cancer, MDPGCC was diagnosed in 54 patients (1.2%). The selected patients were classified into a GP (n = 30) or CP group (n = 24). No statistically significant differences were observed between the two groups with regard to sex, age, operation, location or histological type. No differences were observed in rates of surgery between the two groups. No notable difference was observed in the year-by-year incidence of GP- and CP-MDPGCC as calculated from the date of surgery or chemotherapy for the secondary gastric or colorectal cancer. The 5-year survival rate in the GP- and CP-MDPGCC groups was 84.7% and 83.3%, respectively. No significant difference was observed between the GP- and CP-MDPGCC groups (P = 0.9). There is no significant difference in prognosis between GP- and CP-MDPGCC.