For asymptomatic neoplastic pancreatic cysts discovered incidentally on abdominal imaging, surgery is warranted only if both a solid component and a dilated pancreatic duct are shown and/or if esophageal ultrasound with or without fine-needle aspiration has detected “concerning features,” according to a clinical practice guideline published in the April issue of Gastroenterology (doi:10.1053/j.gastro.2015.01.015).
Even then, patients should be referred for the procedure only to centers that perform high volumes of pancreatic surgery, so as to minimize the relatively high rates of morbidity and mortality associated with these invasive, expensive, and potentially harmful surgeries.
These are 2 of the 10 recommendations and “suggestions” in the American Gastroenterological Association guideline, which is the first such guideline to be based on a systematic evaluation of the available evidence, said Dr. Santhi Swaroop Vege of the division of gastroenterology and hepatology, Mayo Clinic, Rochester, Minn., and his associates.
Incidental discovery of asymptomatic pancreatic cysts is common with the increasing use of sophisticated abdominal imaging techniques. For example, approximately 15% of patients undergoing abdominal MRI for other indications are found to have them. Clinical management is very difficult because only a small fraction of these lesions prove to be malignant, and the data to guide diagnostic and treatment decisions are sparse and of very low quality, based almost entirely on retrospective case series. Nevertheless, Dr. Vege and his associates developed the guideline from the limited evidence that is available, because of the seriousness of the outcomes for that minority of cancers and the complexity of management strategies.
“These recommendations may result in significant controversy, as they advocate less frequent follow-up and a higher threshold before offering esophageal ultrasound and/or surgery. However, consistent utilization should decrease inadvertent harm to patients and reduce the costs of health care delivery,” they noted.
After reviewing the literature, the investigators estimated that an asymptomatic cyst found incidentally on MRI has only a 10 in 100,000 chance of being a mucinous invasive malignancy and a 17 in 100,000 chance of being a ductal cancer. The guideline therefore suggests that surveillance is sufficient for asymptomatic pancreatic cysts smaller than 3 cm that don’t have a solid component or a dilated pancreatic duct. The preferred imaging modality is MRI, and the preferred surveillance interval is at 1 year after discovery. If no change is noted, surveillance every 2 years for a total of 5 years should be sufficient.
The risk of malignant transformation is estimated to be only 0.24% per year, and is even lower among cysts that show no changes over time. “The small risk of malignant progression in stable cysts is likely outweighed by the costs of surveillance and the risks of surgery,” so the guideline suggests that surveillance can be discontinued if no change has occurred after 5 years or if the patient is no longer a candidate for surgery. However, some patients, such as those with a family history of pancreatic cancer, may opt to continue surveillance.
In contrast, asymptomatic pancreatic cysts that have at least two high-risk features should be assessed using esophageal ultrasound, with or without fine-needle aspiration. If these procedures reveal “concerning features,” the benefits of surgery probably outweigh the risks, and surgical excision/resection is conditionally recommended. However, even in these “suspect” lesions only an estimated 17% are found to harbor high-grade dysplasia. Any benefit ascribed to surgery must be balanced against “an overall postoperative mortality of 2% and major morbidity of 30% from our review of the literature,” Dr. Vege and his associates said.
In contrast to its suggestions and conditional recommendations, the AGA guideline strongly recommends that if surgery is being considered, patients be referred to “a center with demonstrated expertise in pancreatic surgery.” Their investigation showed that in the U.S. overall, all pancreatic surgeries carry a postoperative mortality of 6.6%, while in centers of excellence, the postoperative mortality is only 2%.
The guideline conditionally suggests that patients found to have invasive cancer or dysplasia in a resected cyst can undergo MRI surveillance of any remaining pancreas every 2 years, for as long as the patient remains a good candidate for further surgery.
Another recommendation is that patients be given a clear understanding of the benefits and risks of any surveillance program, because surveillance may not be appropriate for some. Certain patients have a high tolerance for risk and may decide against surveillance once the small risk of malignancy is explained to them. Others have a limited life expectancy and are unlikely to benefit from surveillance or surgery, and still others who are poor surgical candidates because of age or comorbidities shouldn’t be subjected to surveillance.
Finally, this AGA guideline pertains only to asymptomatic neoplastic pancreatic cysts. It doesn’t address lesions such as solid papillary neoplasms, cystic degeneration of adenocarcinomas, neuroendocrine tumors, or main duct intraductal papillary mucinous neoplasms without side-branch involvement, because identification of these lesions is more straightforward and the accepted management approach is surgical resection, Dr. Vege and his associates added.