The Relevance of Gallbladder Polyps to Gallbladder Cancer

“Gallbladder cancer is rare, and most cancers do not arise from polyps,” said Dr. Khalili, professor of radiology at the University of Toronto. “On the other hand, polyps are really common, seen in up to nine percent of the population, so managing gallbladder polyps, very few of which will become cancer, is resource intensive, anxiety inducing and may lead to overdiagnosis and overtreatment.” 

Data Showed Larger Polyps Often Meant Surgery or Surveillance

Most gallbladder polyps are identified during other imaging exams as incidental findings. North American and European practice guidelines suggest surveillance for some gallbladder polyps that are smaller than 1 cm. 

To identify the clinical and imaging variables associated with the development of GBCA and assess the risk associated with gallbladder polyps, Dr. Khalili’s team analyzed data from patients with an intact gallbladder who underwent an abdominal US during a 20-year period at three academic institutions in Toronto. 

Imaging data (polyp size and multiplicity, adenomyomatosis, stones, primary sclerosing cholangitis (PSC), porcelain gallbladder and choledochal cysts) was extracted from reports using natural language processing. Gallbladder cancer diagnoses were collected from the provincial cancer registry. 

The cohort included 218,418 patients (mean age 50.7, 55.3% female), 192 of whom presented with or developed gallbladder cancer. Patients were divided into low-risk and high-risk regions based on global incidence data. Of the cohort, 13.6% were from a high-risk country. Gallbladder stones and adenomyomatosis were identified in 11.7% and 2.6% of the patient population, respectively, while the presence of PSC, choledochal cysts and porcelain GB were minimal.

Of patients in the cohort, 21,500 (9.8%) had gallbladder polyps. The majority (89.4%) were 6 mm or smaller. Polyps that were 7-9 mm represented 8.2% of the total. Only 2.4% (406) of patients had polyps 10 mm or larger.

Polyps less than 7 mm in size represented no increased risk of GBCA. Polyps between 7-9 mm were associated with a 0.07% 15-year cumulative risk, which is lower than the mortality risk of cholecystectomy. However, the 15-year cumulative GBCA risk associated with ≥10-millimeter polyps was significant, at 3%. 

“Our study suggests that patients with polyps ≥10 millimeters, or with smaller polyps combined with other risk factors may need surgery or surveillance,” Dr. Khalili said. 

Other factors in the study associated with an increased risk of GBCA were age, gallstones, primary sclerosing cholangitis, choledochal cysts, and being from a high-risk region. Factors that did not increase GBCA risk included chronic liver disease, steatosis and having a single polyp.

“Development of gallbladder cancer from a polyp initially measured at less than 10 millimeters is quite rare,” Dr. Khalili said. “In our cohort, it did not sufficiently increase the risk of subsequent cancer.”

Access the presentation, “The Relevance of Gallbladder Polyps to Gallbladder Cancer in a Cohort of 218,418 Patients,” (R3-SSGI17-4) on demand at RSNA.org/MeetingCentral.