Invasive and Noninvasive Progression After Resection of Noninvasive Intraductal Papillary Mucinous Neoplasms

OBJECTIVE To define frequencies, pattern of progression (invasive versus non-invasive), and risk factors of progression of resected non-invasive IPMNs BACKGROUND:: There is a risk of progression in the remnant pancreas after resection of intraductal papillary mucinous neoplasms (IPMNs). METHODS 449 consecutive patients with resected IPMNs from 1995-2018 were included to the study. Patients with invasive carcinoma or with follow-up < 6 months were excluded. Non-invasive progression was defined as a new IPMN, increased main pancreatic duct (MPD) size, and increased size of an existing lesion (5 mm compared to preoperative imaging). Invasive progression was defined as development of invasive cancer in the remnant pancreas or metastatic disease. RESULTS With a median follow-up of 48.9 months, progression was identified in 124 patients (27.6%); 108(24.1%) with non-invasive and 16(3.6%) with invasive progression. Median progression follow-up was longer for invasive progression (85.4 vs. 55.9 months; P = 0.001). Five- and 10-year estimates for a cumulative incidence of invasive progression were 6.4% and 12.9% versus 26.9% and 41.5% for non-invasive progression. After risk-adjustment, multifocality (HR 4.53, 95%CI 1.34-15.26; P = 0.02) and high-grade dysplasia (HGD) in the original resection (HR 3.60, 95%CI 1.13-11.48; P = 0.03) were associated with invasive progression. CONCLUSIONS Progression to invasive carcinoma can occur years after the surgical resection of a non-invasive IPMN. HGD in the original resection is a risk factor for invasive progression but some cases of low-grade dysplasia also progressed to cancer. Patients with high-risk features such as HGD and multifocal cysts should be considered for more intensive surveillance and represent an important cohort for future trials such as anti-inflammatory or prophylactic immunotherapy.