Only 1% of adults with asymptomatic neoplastic pancreatic cysts developed invasive pancreatic adenocarcinoma after more than 5 years of follow-up, according to a multicenter retrospective study reported in the June issue of Clinical Gastroenterology and Hepatology.

Furthermore, there were no malignant conversions among patients lacking American Gastroenterological Association high-risk features – that is, mural nodules, dilated pancreatic ducts, or cysts measuring more than 3 cm, said Dr. Wilson Kwong at the University of California San Diego Health Sciences in La Jolla. “There is a very low risk of malignant transformation of asymptomatic neoplastic pancreatic cysts after 5 years,” he and his associates wrote.

Up to 20% of cross-sectional imaging studies reveal incidental pancreatic cysts, the researchers noted. Cysts with neoplastic features are recommended for indefinite surveillance, even though there is little or no data on their natural history and malignant potential beyond 5- 10 years, they added. Therefore, they studied 310 patients who underwent endoscopic ultrasound of pancreatic cysts at an academic medical center, a Veterans’ Affairs hospital, and two community health care systems in California between 2002 and 2010. The most common age at enrollment was 66 years, 60% of patients were women, and the median follow-up period was 87 months (range, 60 to 189 months). A total of 90% of patients were followed for 5-10 years, while 10% were followed for more than 10 years (Clin Gastroenterol Hepatol. 2016 Feb 10. doi: 10.1016/j.cgh.2015.11.013 ).

In all, three patients developed invasive pancreatic malignancies after 6, 8, and 11 years of follow-up, for an overall conversion rate of 1%. Conversion rates by subgroup were 0% for patients with no high-risk AGA features, 1% (one case) for patients with one high-risk feature, and 15% (two cases) for patients with two high-risk features. “Because the risk of malignant transformation beyond 5 years is lower than the 1.4% mortality risk of pancreatic resection at high-volume centers, the argument can be made that discontinuing surveillance after 5 years is justified,” the researchers said. Specifically, surveillance could be discontinued after 5 years for neoplastic pancreatic cysts with up to one high-risk feature, particularly if patients have significant comorbidities that increase their risk of imminent death from other causes, they added. In contrast, healthy patients in their 60s and 70s might benefit from long-term surveillance given their longer life expectancy, they said. “Among patients with two high-risk features who remain surgically fit, discussion of surgery or surveillance beyond 5 years should be considered,” they emphasized.

A total of two patients developed high-grade dysplasia – a risk factor for invasive pancreatic cancer – but even so, the aggregate rate of cancer and high-grade dysplasia was 1.6%, only slightly higher than the fatality rate associated with pancreatic resection, the researchers noted. By excluding patients with recent acute pancreatitis (because of the likelihood of pseudocysts), they might have inadvertently excluded “a small number” of patients with pancreatic intraductal papillary mucinous neoplasms, they added.

The University of California San Diego Health Care System supported the study. The investigators had no disclosures.


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