Independent of Primary Sclerosing Cholangitis and Cirrhosis, Early Adulthood Obesity Is Associated with Cholangiocarcinoma.

BACKGROUND: It is estimated that 6% to 20% of all cholangiocarcinoma (CCA) diagnoses are explained by primary sclerosing cholangitis (PSC), but the underlying risk factors in the absence of PSC are unclear. We examined associations of different risk factors with intrahepatic cholangiocarcinoma (ICC) and extrahepatic cholangiocarcinoma (ECC) in the United States. METHODS: We conducted a case-control study of 121 patients with ECC and 308 patients with ICC treated at MD Anderson Cancer Center between May 2014 and March 2020, compared with 1,061 healthy controls. Multivariable logistic regression analysis was applied to estimate the adjusted OR (AOR) and 95% confidence interval (CI) for each risk factor. RESULTS: Being Asian, diabetes mellitus, family history of cancer, and gallbladder stones were associated with higher odds of developing ICC and ECC. Each 1-unit increase in body mass index in early adulthood (ages 20-40 years) was associated with a decrease in age at diagnosis of CCA (6.7 months, P < 0.001; 6.1 months for ICC, P = 0.001; 8.2 months for ECC, P = 0.007). A family history of cancer was significantly associated with the risk of ICC and ECC development; the AORs (95% CI) were 1.11 (1.06-1.48) and 1.32 (1.01-2.00) for ICC and ECC, respectively. CONCLUSIONS: In this study, early adulthood onset of obesity was significantly associated with CCA and may predict early diagnosis at younger age than normal weight individuals. IMPACT: The study highlights the association between obesity and CCA, independent of PSC. There is a need to consider the mechanistic pathways of obesity in the absence of fatty liver and cirrhosis.