Introduction : With increasing detection of intraductal papillary mucinous neoplasms(IPMN), a tailored approach is needed. We explored the natural history of IPMN and suggest optimal treatment based on malignancy risk using nomogram and Markov decision model.

Methods : Patients diagnosed with IPMN, who underwent surveillance or surgery, were included. Change of worrisome features/high risk stigmata and malignancy conversion rate was calculated through radiologic and pathologic reviews. Through the application of a nomogram predicting malignancy life expectancy were compared.

Results : Of 10,614 patients suspected to have IPMN, histologic confirmed or radiologically typical 2,006 patients were enrolled. Of these, 1,773(88.4%) had branch duct (BD), 81(4.0%) had main duct and 152(7.6%) had mixed type at initial diagnosis. The cumulative risk of developing worrisome feature/ high-risk stigmata was 19.0% at 5-year and 35.0% at 10-year- follow-up. The progression of malignancy rate at 10-year follow-up was 79.9% for main and mixed type IPMN and 5.9% for BD-IPMN. Nomogram based malignancy risk prediction is well correlated with natural history based on pathologic biopsy and shows good stratification of the survival. Decision model recommends surgery to maximize overall survival and quality-adjusted life year for patients under 75-years old, especially those with over 35% malignancy risk.

Conclusions : Compared to the high risk of malignancy(79.9%) in main and mixed type IPMN, that(5.9%) of BD-IPMN are very indolent. The decision model based on nomogram suggests operation rather than surveillance for patients with high malignancy rate. Optimal treatment strategy between operation and surveillance should be carefully considered based on patient’s health status, malignancy risk