Smoking, drinking and colorectal cancer in Hong Kong Chinese: a case-control study

Expert opinions differ on the causal role of cigarettes and alcohol in colorectal cancer. This study investigates such associations in Hong Kong Chinese. A hospital-based case-control study was conducted from April 1998 to March 2000. Newly diagnosed colorectal adenocarcinoma and sex- and age-matched inpatient controls without gastrointestinal and malignant conditions were included. Structured interviews were conducted using a validated questionnaire to study any association of smoking, drinking and the lifelong extent of such exposures with colorectal cancer risk. We successfully interviewed 822 cases and 926 controls. Current regular cigarette smokers had an increased rectal cancer risk (adjusted OR = 1.44; 95% CI = 1.001-2.06). Increasing tertiles of smoking duration in ever smokers was also associated with increased rectal cancer risk (p trend = 0.038). An increased risk of colorectal cancer was found in current drinkers (adjusted OR = 1.42; 95% CI = 1.09-1.85) and in those who drank > or = 4 days (current and ex-drinkers) or > 4 units (ever and ex-drinkers) weekly. Moreover, colorectal cancer risk was found to decrease with increasing duration of drinking abstention (p trend = 0.006). This is the first report of a positive association between cigarette smoking and rectal cancer risk in a Chinese population. Current drinkers and those who drank regularly and heavily had increased colorectal cancer risk. Moreover, this study is the first to show that drinking cessation could be effective in reversing such increased risk in a duration-dependent manner. These new findings are important for cancer prevention and healthcare promotion.