Abdominal ultrasound scan for the follow-up of pancreatic cystic lesions: could it play a role as a safe and cost-saving alternative to the routine MRI?

Objectives: Patients with pancreatic cystic lesions (PCL) without “worrisome features”(WF) at the diagno-sis,usually necessitate a lifetime surveillance with a MRI to monitorcysts size, pancreatic main duct dilatation or mural nodules. Since these parameters can also be evaluated with an ultrasound(US) scan, we studied safety, feasibility and economic impact of an abdominal US scan follow-up, with a delayed use of MRI. Methods: We retrospectively evaluated data of all the patients underwentan abdominal US scanas follow-up for “low risk” PCL in our institution. We performeda US scan every six months for the first year and then,in case of stable disease,annually from the second to the fifth year. A surveillance MRI scan was routinely performed every two years, or in presence of considerable modifications at US. We compared the two imaging techniques regarding sensitivity and specificity in identifying cysts variations. We also focused on a costs-analysis between the theoretical application of the international guidelines and our follow-up strategy with abdominal US scan and delayed MRI. Results: Two-hundred patients with PCL were followed-up with abdominal US scan between January 2012 and January 2016,138 (69%) females and 62 (31%) males. Mean follow-up period was 25.1 months (±18.2). Two patients (1%) needed surgery for the appearance of WF at imaging (with concordance among US and MRI). During the follow-up, US showed “low grade” modifications in 28 patients (14%), included main pancreatic duct dilatation <6mm and increasing of the main cyst of about 0.5cm. In all of these cases MRI confirmed US findings, without adding more prognostic information.In only 11 patients (5.5%) a routine MRI identified an evolution of the lesions,not showed at US, but only related to an increased number of the PCL (p=0.14). Nevertheless, a MRI every 6 months would not have changedthe decisional process. The mean cost of surveillance for each patient, in a theoretical applicationofinternational guidelines with MRIfollow up at our group of patients, should have been 402±273.7 €, while according to our follow-up strategy it was 215.4±212.6 € (p< 0.0001). Conclusion: In patients with PCL without WF, abdominal US could be a safe alternative to MRI, reducing the numbers of II level examinations and therefore reducing costs. Long term safety of this approach should be validated on a longer follow-up period, with a larger series of patients and prospective studies.