Background: Intraductal papillary mucinous neoplasm (IPMN) of the pancreas has been recognized recently and is being diagnosed with increasing frequency. Although IPMN has a more favorable prognosis than standard invasive ductal carcinoma (IDC) of the pancreas, recent reports suggest that IPMN patients are at higher risks of synchronous or metachronous primary cancers arising from various organs other than the pancreas (extrapancreatic cancers). Methods: Records of 370 patients (69 of IPMN, 301 of IDC) who underwent surgery were used to assess risk factors for preoperative or postoperative extrapancreatic cancers. To calculate the rate of increase of extrapancreatic cancers in IPMN patients, compared with the normal population, the observed/expected ratio (O/E ratio) was calculated by using the Osaka Cancer Registry, one of the world largest cancer databases. Results: The incidence of preoperative extrapancreatic cancers was significantly higher in IPMN patients (28%, 19 patients) than that in IDC (9%, 27 patients). In the IPMN-group, the preoperative incidence of colorectal cancer was 12% followed by gastric cancer at 4%. Logistic regression analysis showed IPMN and age to be independent risk factors for preoperative colorectal cancer development. The O/E ratio of preoperative colorectal cancer was significantly high in IPMN patients (5.37; 95% confidence interval, 2.31-10.58) but not in IDC patients (1.24; 95% confidence interval, 0.46-2.70). The incidence of postoperative extrapancreatic cancers also was significantly higher in IPMN patients (15%, 10 patients) than that in IDC (4%, 12 patients). During the postoperative follow-up, 4% of IPMN (3 patients) and 0.7% of IDC (2 patients) died from extrapancreatic cancers. Conclusions: Our results indicate that IPMN patients are at significantly higher risks of extrapancreatic cancers including colorectal cancer. A careful systemic checkup is therefore required for preoperative screening and postoperative follow-up for IPMN patients.
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