Consequences of a Surveillance Strategy for Side-Branch Intraductal Pancreatic Mucinous Neoplasms: Long-Term Follow-Up of One-Thousand Cysts.

ABSTRACT

OBJECTIVE: We aim to quantify the rate of progression in surveilled cysts and assess what factors should indicate delayed resection. SUMMARY BACKGROUND DATA Side-branch intraductal papillary mucinous neoplasms (SB-IPMNs) are increasingly discovered, making it challenging to identify which patients require resection, thus avoiding inappropriate treatment. Most incidental lesions are surveyed, yet the consequences of that decision remain uncertain. METHODS: A prospectively maintained database of pancreatic cystic neoplasms was queried for patients with SB-IPMN. Patients with ≥2 imaging studies >6 months apart were included. Clinically relevant progression (CR-Progression) was defined by symptoms, worrisome/high-risk stigmata, or invasive cancer (IC). Growth ≥5 mm in 2 years is considered CR-Progression; size ≥3 cm alone is not. RESULTS: Between 1997-2023,1,337 patients were diagnosed with SB-IPMN. Thirty-seven (2.7%) underwent up-front surgery; 1,000 (75.0%) had >6 months surveillance.The rate of CR-progression was 15.3% (n=153) based on size increase (n=63, 6.3%), main-duct involvement (n=48, 4.8%), symptoms (n=8, 5.0%), or other criteria (n=34, 3.4%). At a median follow-up of 6.6 years (IQR 3.0-10.26), 17 patients (1.7%) developed IC. Those with CR-progression developed IC in 11.1% (n=17) and high-grade dysplasia (HGD) in 6.5% (n=10). Nearly half of the cancers were not contiguous with the surveyed SB-IPMN.Size ≥3 cm was not associated with HGD/IC (P=0.232). HGD/IC was least common in CR-progression determined by size growth (6.3%) versus main-duct involvement (24%) or other (43%, P<0.001)Patients with CR-progression demonstrated improved survival (OS) with resection on time-to-event (P<0.001) and multivariate cox-regression (HR=0.205, 0.096-0.439, P<0.001) analyses. OS was not improved with resection in all patients (P=0.244). CONCLUSION: Clinically relevant progression for SB-IPMNs is uncommon with development of cancer anywhere in the pancreas being rare. Initial size should not drive resection. Long-term and consistent non-operative surveillance is warranted, with surgery currently reserved for CR-progression knowing that the majority of these still harbor low grade pathology.