Natural history and optimal treatment strategy of intraductal papillary mucinous neoplasm of the pancreas: Analysis using a nomogram and Markov decision model.

Background/purpose: With the increase in detection of intraductal papillary mucinous neoplasms (IPMN), a tailored approach is needed. This study was aimed at exploring the natural history of IPMN and suggest optimal treatment based on malignancy risk using a nomogram and Markov decision model.

Methods: Patients with IPMN who underwent surveillance or surgery were included. Changes in worrisome features/high-risk stigmata and malignancy conversion rate were assessed. Life expectancy and quality-adjusted life year (QALY) were compared using a nomogram predicting malignancy.

Results: Overall, 2006 patients with histologically confirmed or radiologically typical IPMN were enrolled. Of these, 1773 (88.4%), 81 (4.0%), and 152 (7.6%), respectively, had branch duct (BD)-, main duct-, and mixed-type IPMN at initial diagnosis. The cumulative risk of developing worrisome feature or high-risk stigmata was 19.0% and 35.0% at 5- and 10-year follow-up, respectively. The progression of malignancy rate at 10-year follow-up was 79.9% for main and mixed IPMNs 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 survival. The decision model recommends surgery to maximize survival and QALY especially in those with >35% malignancy risk.

Conclusions: Compared with main duct- and mixed-type IPMN, which have a high risk of malignancy (79.9%), BD-IPMN is very indolent (5.9%). The nomogram-based decision model suggests surgery rather than surveillance for patients with a high malignancy risk. The optimal treatment strategy between surgery and surveillance should consider patients' health status, malignancy risk, and centers' experience.