Gallbladder Polyps Not Associated With Long-Term Gallbladder Cancer Risk

By Lisa Rappaport

May 19, 2020

(Reuters Health) - Gallbladder cancer is rare, and the long-term risk of these malignancies doesn't appear much different for people with a history of gallbladder polyps, a new U.S. study suggests.

Researchers examined data on 622,227 adults who had undergone gallbladder ultrasonography as members of Kaiser Permanente Northern California between 1995 and 2014, including 365 with gallbladder cancer.

Overall, gallbladder polyps were found in 22 patients (6.0%) in the gallbladder cancer cohort and in 35,870 (5.8%) controls.

The risk of gallbladder cancer was similarly low with or without polyps. Just 0.053% of adults with polyps later were diagnosed with gallbladder cancer, compared with 0.054% of adults without polyps.

"Overall, you're just as likely to get gallbladder cancer if you have a polyp or not," said study co-author Dr. Jean-Luc Szpakowski of Kaiser Permanente Northern California in Fremont.

"We also found that it appears to be in the nature of these polyps to grow over time, and even if they don't appear to grow over 3 or 5 years, if you follow them longer, they will grow," Dr. Szpakowski said by email.

This means that for all but the largest polyps, doing annual ultrasounds with the goal of finding a warning sign of cancer and then removing the gallbladder is not an effective strategy, Dr. Szpakowski added. This approach doesn't necessarily prevent cancer, and it exposes patients to the risk of surgery and racks up annual costs for expensive ultrasounds, Dr. Szpakowski said.

"A subgroup of larger polyps, over one centimeter, are at slightly higher risk, but even then, the risk of gallbladder cancer is very low, and most were found in the first year after ultrasound," Dr. Szpakowski concluded.

The unadjusted gallbladder cancer rate was just 1.3 cases per 100,000 person-years when gallbladder polyps had an initial size of less than 6mm. By contrast, the unadjusted gallbladder cancer rate was 128.2 cases per 100,000 person-years for individuals who had initial gallbladder polyps of 10mm or larger.

After 10 years of follow-up, the unadjusted cumulative probability of polyp growth of at least 2mm was 66.2% among people who were initially diagnosed with polyps of less than 6mm, researchers also found. Among people who had initial polyps of 6mm to 10mm, 52.9% had the polyps grow at least 2mm over 10 years.

The authors did not report adjusted probabilities. Another limitation of the study is that researchers only looked at ultrasound-detected polyps, and it's possible there were errors in the interpretation of ultrasound images in some cases, the study team notes in JAMA Network Open. There is also a possibility that some people in the study had undetected gallbladder cancer.

Even so, the results should reassure patients that the absolute risk of gallbladder cancer is low, even with polyps, said Dr. Aliya Gulamhusein, of the University of Toronto in Ontario.

"However, certain patient risk factors including older age and underlying conditions and imaging factors including larger polyps must inform risk stratification, surveillance strategies, and clinical management," Dr. Gulamhusein, who wasn't involved in the study, said by email.

At-risk populations including should continue to be managed with surveillance imaging and offered cholecystectomy for large polyps or masses, particularly in light of the poor outcomes associated with gallbladder cancer, Dr. Gulamhusein said.

"These data do not suggest otherwise," Dr. Gulamhusein added. "That said, younger patients without high risk underlying conditions with small gallbladder polyps are likely to be at low risk of gallbladder cancer, and the utility and cost effectiveness of long term imaging surveillance remains in question."

SOURCE: JAMA Oncology, online May 18, 2020.