Branch-duct intraductal papillary mucinous neoplasms (BD-IPMNs) grew at a median annual rate of 0.8 mm in a retrospective study of 1,369 patients.

While most of these cysts were “indolent and dormant,” some grew rapidly and developed “other worrisome features,” Youngmin Han, MS, of Seoul (South Korea) National University reported with his associates in the February issue of Gastroenterology . Therefore, clinicians should plan follow-up surveillance based on initial cyst size and growth rate, they concluded.

Based on their findings, the researchers recommended surgery for young, fit, asymptomatic patients who have BD-IPMNs with a diameter of least 30 mm or with thickened cyst walls or those who have a main pancreatic duct measuring 5-9 mm. Surgery also should be considered when patients have lymphadenopathy, high tumor marker levels, or an abrupt change in pancreatic duct caliber with distal pancreatic atrophy or a rapidly growing cyst, they said.

For asymptomatic patients whose cysts are under 10 mm and who do not have worrisome features, they recommended follow-up with CT or MRI at 6 months and then every 2 years after that. Cysts of 10-20 mm should be imaged at 6 months, at 12 months, and then every 1.5-2 years after that, they said. Patients with cyst diameters greater than 20 mm “should undergo MRI or CT or EUS [endoscopic ultrasound] every 6 months for 1 year and then annually thereafter, until the cyst size and features become stable,” they added. Patients whose cysts have a diameter of 30 mm or greater “should be closely monitored with MRI or CT or EUS every 6 months. Surgical resection can be considered in younger patients or those with other combined worrisome features.”

To characterize the natural history of BD-IPMN, the investigators evaluated clinical and imaging data collected between 2001 and 2016 from patients with classical features of BD-IPMN. Each patient included in the study provided 3 or more years of CT, MRI, EUS, and endoscopic retrograde cholangiopancreatography data. The researchers used regression models to estimate changes in sizes of cysts and main pancreatic ducts.

Median follow-up time was 61 months (range, 36-189 months). Cyst diameter averaged 12.8 mm (standard deviation, 6.5 mm) at baseline and 17 mm (SD, 9.2 mm) at final measurement. Larger baseline diameter was associated with faster growth (P = .046): Cysts measuring less than 10 mm at baseline grew at a median annual rate of 0.8 mm (SD, 1.1 mm), while those measuring at least 30 mm grew at a median annual rate of 1.2 mm (SD, 2.1 mm).

Worrisome features were present in 59 patients at baseline and emerged in another 150 patients during follow-up. At baseline, only 2.3% of cysts exceeded 30 mm in diameter, but 8.0% did at final measurement. Cyst wall thickening was found in 0.5% of patients at baseline and 3.7% of patients at final measurement. Main pancreatic ducts measured 5-9 mm in 1.9% of patients at baseline and in 5.6% of patients at final measurement. Additionally, the prevalence of mural nodules rose from 0.4% at baseline to 3.1% at final measurement.

Main pancreatic ducts averaged 1.8 mm (SD, 1.0 mm) at baseline and 2.4 mm (SD, 1.8 mm) at final measurement. Compared with the values seen with smaller cysts, larger baseline cyst diameter correlated significantly with larger main pancreatic ducts, more cases of cyst wall thickening, and more cases with mural nodules (P less than .001 for all comparisons).

The study was funded by a grant from Korean Health Technology R&D Project of Ministry of Health and Welfare, Republic of Korea. The investigators reported having no conflicts of interest.

SOURCE: Han Y et al. Gastroenterology. 2018. doi: 10.1053/j.gastro.2017.10.013 .