Natural History of Branch-Duct Type Intraductal Papillary-Mucinous Tumor (IPMT) of the Pancreas: ‘Prospective’ Long-Term Follow-Up By MR Cholangiopancreatography (MRCP) and EUS

Abstract

Background/Aims: In patients with branch-duct type IPMT, we previously demonstrated that MRCP can identify features suggestive of malignancy, such as cystic lesions larger than 30 mm and/or presence of a mural nodule (Gastrointest Endosc supple.53; AB175,2001). In this study, we examined the role of MRCP and EUS in the follow-up of these patients and focused on changes in the size of the cystic branch and emergence of mural nodules. Methods: After providing informed consent, 37 patients with branch-duct type IPMT diagnosed by ERCP were enrolled in this prospective study. Five patients with cystic lesions larger than 30 mm and 2 patients suspected to have mural nodule(s) at an initial examination who refused surgical intervention were also included in this study. Patients were surveyed by MRCP, EUS, and CT at least once a year. Results: An increase in the size of cystic lesions by either MRCP or EUS was demonstrated in 7 patients (18.9%), which was consistent with findings on CT. However, there were discrepancies in other cases; the size of cystic lesions was overestimated by EUS in 2 cases when compared to CT and MRCP, and underestimated in 6 cases because of inadequate visualization of entire lesion. Emergence of a new mural nodule was identified in 2 cases by both MRCP and EUS. The 2 cases of mural nodules that were present at initial examination did not increase in size on serial MRCP and EUS examinations during a 103.0 +/− 2.0 month follow-up. Surgical resection was performed because of an increase in size of the cystic lesion in 2 cases and emergence of a new mural nodule in 2 cases after 11 to 25 months of follow-up (mean 16.8 months). These were histologically diagnosed as adenoma in 3 patients and non-invasive adenocarcinoma in 1. The remaining 33 patients who did not have surgery were monitored for 36 to 138 months (mean 64.3 +/− 39.4 months). In 2 of 5 patients (40%) with a cystic lesion larger than 30 mm and 4 of 32 (12.5%) patients with lesions <30 mm, the size increased more than 20%. MRCP identified new or multiple IPMT lesions in 13 patients (21 lesions), but EUS missed 4 (19%) of them. No metastatic lesions associated with IPMT were identified, but two patients died of other causes. Conclusions: Branch-duct type IPMTs without mural nodules usually grow slowly and can be followed by serial imaging studies, even in cases with a large cystic lesion. MRCP is a useful modality to monitor the changes in size of the cystic lesions, as well as to identify multicentric lesions. We conclude that MRCP may be equivalent to EUS for surveillance in patients with branch-duct type IPMT.