Background: Colorectal cancer (CRC) is one of the most common cancers worldwide. This study aimed to investigate the interaction between the presence of a polymorphism of the XRCC1 gene and known risk factors for colorectal cancer in Thailand. Materials and Methods: A hospital-based case-control study was conducted in Thailand. The participants were 230 histologically confirmed new cases and 230 controls matched by sex and age and recruited from the same hospital. Information about demographic characteristics, life style, anddietary habits was collected using structured interviews, and blood samples were taken which were used for the detection of a homozygous and heterozygous polymorphisms of XRCC1. Associations were assessed using multiple conditional logistic regression. Results: In the univariate analysis, factors found to be significantly associated with an increased risk for CRC were the presence of the XRCC1 AA homozygote (OR= 4.95; 95% CI: 1.99-12.3), a first degree family history of cancer (OR= 1.74; 95% CI: 1.18-2.58), and a high frequency ofpork consumption (OR= 1.49; 95% CI: 1.00-2.21). Intakes of fish fruit and vegetables appeared to be protective factors, but the associations were not statistically significant. In the multivariate analysis only the XRCC1 AAhomozygote polymorphism and a family history of cancer emerged as risk factors (OR= 4.96; 95% CI: 1.90-12.95 and OR=1.80; 95% CI: 1.18-2.72, respectively). Conclusions: While the XRCC1 AA homozygote and a family history of cancer were found to be associated with an increased risk of CRC, none of the dietary intake variables were clearly identified as risk or protective factors. There is a need for further research to determine the reasons for this.
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