Pesticide exposure and risk of cholangiocarcinoma: A hospital-based matched case-control study

Cholangiocarcinoma (CCA) caused by Opisthorchis viverrini is a well-known and significant public health issue in northeastern Thailand; however, a link between pesticide exposure (PE) and CCA risk has not yet been established. Therefore, our research objective was to investigate the relationship between PE and CCA risk.

A hospital-based matched case-control study was carried out. All cases (in-patients) and controls (out-patients) were volunteers at a tertiary hospital in northeast Thailand. Between 2015 and 2019, 178 incident cases of pathologically-confirmed CCA and 356 controls were selected from the check-up clinic from the Srinagarind Hospital outpatient database (two controls per case). The recruited controls were individually-matched to the CCA cases based on sex, age (±5 years) and admission date (±3 months). During face-to-face interviews, a standardised pre-tested questionnaire was used to collect data. Multivariable conditional logistic regression was used to analyse the data.

The respective frequency of PE between the 178 CCA cases and 356 controls was 77.0% versus 87.6% for never used, 14.6% versus 5.3% for have used but stopped and 8.4% versus 7.0% for currently using. After adjusting for the highest educational attainment, smoking behaviour, alcohol use and family history of cancer, PE was not significantly associated with CCA (p-value = 0.086). Using volunteers who have never used PE as the reference group, the respective odds of developing CCA for those who have ever used but have since stopped and are currently using was 2.04 (adjusted OR = 2.04; 95% CI: 1.03-4.04) versus 0.83 (adjusted OR = 0.83; 95% CI: 0.39-1.76) times more likely to develop CCA than those who had never used PE.

There is no association between PE and the risk of CCA. Notwithstanding the finding, future research should focus on enhancing PE assessment methods that consider complex chemical mixtures, chemicals of interest, historical exposure and exposure pathways. Moreover, there is need for more extensive and longer population-based cohort studies that include younger, non-occupationally exposed individuals during periods of developmental susceptibility.