RESUMO
BACKGROUND: The incidence of colorectal cancer is variable around the world. Hiroshima, Japan had the highest incidence in men in 1997 with an age-standardized rate of 86.7 per 100,000 and New Zealand had the highest, at 40.6 per 100,000, in women. The incidence of colorectal cancer in Thailand is rather low and the latest figures for Northeast of Thailand are 7.1 per 100,000 for men and 4.7 for women. The reasons for these differences between countries are possibly due to variation in dietary habits, alcohol drinking or other cofactors. METHODS: A case-control study was conducted in Khon Kaen, Northeast Thailand during 2002-2006 to study risk factors for colorectal cancer in a low risk area. Totals of 253 colorectal cancer cases (males 135, females 118) and 253 age- and sex-matched controls were recruited. Information on dietary habits, alcohol drinking, smoking and other information were collected by a structured questionnaire. Blood samples were collected for further study. Both univariate and multivariate analyses were carried out. RESULTS: In the final model of multivariate analysis, the significant risk factors for colorectal cancer were a family history of cancer (OR=1.9 95%CI=1.2-2.9) and meat consumption (OR=1.0 95%CI=1.0007-1.0026). For BMI, subjects with higher BMI unexpectedly had a lower risk of colorectal cancer (OR=0.5 95%CI=0.3-0.8). CONCLUSION: Our study confirmed risk factors for colorectal cancer i.e. meat consumption and cancer in the family (genetic problem). However, the results for BMI are the reverse of expected, underlining one limitation of hospital-based case-control studies, in which cases are ill and admitted to the hospital at late stage.