NAACCReview

Study Rationale: Biliary tract cancers are rare but deadly cancers.  They include malignancies of the gallbladder, ampulla of Vater, and intrahepatic and extrahepatic bile ducts.  A recent study in the United States reported increasing incidence of gallbladder cancer among people under 45 years-old and blacks, raising questions of what might be underlying these trends and whether similar incidence patterns are present at other sites within the biliary tract.  To date, most biliary tract cancer descriptive epidemiology studies examined either gallbladder cancer, which is the most common, or analyzed rates and trends for all biliary tract cancers combined.

Study:  Using population-based data from 38 NAACCR registries (AL, AK, AZ, CA, CO, CT, DE, FL, GA, HI, ID, IN, IA, KY, LA, ME, MA, MI, MO, MN, NE, NH, NJ, NY, NC, ND, OH, OK, OR, PA, RI, SC, TX, UT, WA, WV, WI, and WY), we calculated age-adjusted incidence rates, incidence rate ratios, and estimated annual percent change per year for 1999 to 2013 by cancer site and demographic group.

What We Learned:  Gallbladder cancer incidence rates increased among adults under 45 years-old and among non-Hispanic blacks, but decreased among all other demographic subgroups.  Gallbladder cancer incidence rate ratios showed larger differences between females and males aged 18 to 44 years-old.  In contrast, intra-hepatic and extrahepatic cholangiocarcinoma incidence rates steadlily increased between 1999 and 2013 for both genders and across age groups.  Ampulla of Vater cancer increased among males and females under 45 years.

Implications of These Findings:  The differential biliary tract cancer incidence rates and trends by demographic group across anatomic sites indicate that these cancers need to be evaluated separately.  One explanation for the larger differences in gallbladder cancer incidence rates by sex and race/ethnicity among adults 18 to 44 years-old might be changing prevalence of certain risk factors, such as obesity and gallstones, among some demographic groups.   Given the rarity of these cancers, only projects that pool data across multiple longitudinal studies will provide sufficient power to draw meaningful conclusions.

Future Work: The Biliary Tract Cancers Pooling Project (BiTCaPP) is one such effort being led by Dr. Jill Koshiol, Earl Stadtman Investigator in the Infections and Immunoepidemiology Branch of the Division of Cancer Epidemiology and Genetics and the National Cancer Institute, part of the National Institutes of Health.

The opinions expressed in this article are those of the authors and may not represent the official positions of NAACCR.