To ultrasound or not: Polyp size could guide US surveillance decision

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The size of gallbladder polyps should guide follow-up strategy, as large lesions at baseline were more likely to progress and become malignant, according to a study published online Aug. 20 in Archives of Surgery.

Treatment of patients with gallbladder polyps is difficult, explained Giuseppe Garcea, MD, and colleagues from University Hospitals of Leicester in Leicester, England. Up to 95 percent of gallbladder lesions are benign, however, gallbladder cancer has an exceptionally poor survival rate, so the minority of polyps with the potential to progress represent a serious concern.

“The difficulty in deciding on an appropriate management algorithm for gallbladder polyps reflects their relative rarity and the lack of knowledge regarding their natural history and hence the actual risk of malignancy from a putative true polyp within the gallbladder,” wrote the authors. They also noted the difficulty in imaging the gallbladder wall, resulting in stones being mistaken for polyps.

In an attempt to better define management strategies for gallbladder polyp patients, Garcea and colleagues conducted a retrospective analysis featuring 986 patients, 467 of whom underwent further follow-up, between 2000 and 2011. The size of lesions at baseline and their growth were tracked, and the cost-effectiveness of ultrasonography (US) surveillance was examined.

More than two-thirds of the polyps were less than 5 mm in size, 26.2 percent were between 5 and 10 mm, and the rest were larger than 10 mm. One polyp was detected in 62 percent of patients, with more than three polyps detected in nearly 25 percent of patients.

The authors reported that that an increase in size was seen in 6.6 percent of polyps, a decrease was seen in 25.7 percent, with no change in the remaining two-thirds. The median starting size for polyps that demonstrated progression was 7 mm vs. 5 mm. Polyps larger than 10 mm at baseline were more likely to be malignant or potentially so, and had an area under the curve of 0.81.

On the question of cost-effective management, Garcea and colleagues looked at the costs of blanket US surveillance compared with the overall associated costs of gallbladder cancer in order to see if the added expense of surveillance outweighed the costs of polyps progressing to cancer.

Based on their analysis, the authors concluded the annual cost of surveillance, including the costs of surgery to remove potentially malignant polyps, was $310,167 per 1,000 patients per year. The approach would prevent 5.4 incidences of gallbladder cancer per 1,000 patients annually. Since annual costs for a gallbladder cancer patient are approximately $94,000, a total of $508,000 in costs would be prevented. Factoring in the cost of surveillance, the approach nets approximately $200,000 in savings per 1,000 patients per year, according to the authors.

Savings could be increased by surveying only the polyps that were greater than 5 mm at presentation, they continued.

“The incidence of true neoplastic polyps is low,” wrote Garcea and colleagues. “Polyps less than 5 mm can probably be ignored, although regular [US] surveillance is still likely to be cost-effective in this group.” They cautioned that all gallbladder polyps could represent potentially premalignant disease and warrant discussion during a hepatobiliary multidisciplinary team meeting to standardize management.