Risk factors of cholangiocarcinoma in areas not endemic for liver fluke infection.

Background: Thailand has the world's highest prevalence of cholangiocarcinoma (CCA), especially in the endemic area of liver fluke Opisthorchis viverrini infection. However, other regions of Thailand still have relatively high CCA prevalence.

Objectives: We aimed to determine CCA risk factors in areas not endemic for OV infection.

Methods: A case--control study was performed at a referral center during December 2016-December 2017. We collected blood samples and information from CCA patients and identified them as cases. The control group comprised patients who visited a gastrointestinal clinic for colorectal cancer screening colonoscopy. Logistic regression analysis was used to determine risk factors for CCA.

Results: Of 138 participants, O. viverrini infection rate was higher in the case than in the control group (57.1% vs. 36.1%, P = 0.023). Male, O. viverrini infection, smoking, alcohol consumption, and biliary tract diseases were independent risk factors, whereas diabetes, obesity, and cirrhosis were not associated with CCA. By age and sex-adjusted analysis, chronic biliary tract diseases, especially choledochal cysts and smoking, were risk factors for CCA, with adjusted odds ratio (aOR) of 12.7 (95% confidence interval [CI]: 1.4-116.9) and 3.8 (95% CI: 1.3-11.8), respectively, while O. viverrini infection became insignificant risk for CCA (aOR 1.8, 95% CI: 0.8-4.1).

Conclusions: In contrast with endemic areas for O. viverrini infection, chronic biliary tract diseases and smoking are major risk factors, whereas O. viverrini infection has trivial contribution to the development of CCA.