Smoking, alcohol consumption and the risk of cancer of the biliary tract; a population-based case-control study in The Netherlands.

Although cancer of the biliary tract is a highly fatal disease, the relationship with modifiable, life style-related factors is hardly studied. Between 1984 and 1987 we conducted a case-control study of 114 patients and 487 controls from the general population. An interviewer-administered questionnaire was used to collect information on life-time smoking habits and life-time alcohol consumption. The information was obtained either from the subjects themselves (direct response) of from relatives (indirect response). Results show that neither smoking at the time of interview (odds ratio (OR) 1.5; 95% confidence interval (CI) 0.9-2.4) nor smoking 2, 5 or 10 years before were associated significantly with the cancer. Alcohol consumption at the time of interview (OR 1.0; 95% CI 0.6-1.5) or drinking 2, 5 or 10 years before were not significantly associated either. Among current alcohol drinkers, long-term consumers had a reduced risk (duration of use > 38 years vs < 25 years: OR 0.4; 95% CI 0.1-0.9) and late starters an elevated risk (starting age > 38 years vs < 21 years: OR 2.7, 95% CI 1.0-7.5). A modifying effect of alcohol consumption on the smoking-cancer relationship was observed: the risk for current smokers was increased only when they did not drink alcohol at that point in time (OR 3.4, 95% CI 1.3-8.5). Our results indicate that long-term moderate alcohol use might be protective against cancer of the biliary tract, whereas smoking might be a risk factor for this cancer.