DNA repair has an essential role in protecting the genome from damage by 
endogenous and environmental agents. Polymorphisms in DNA repair genes and 
differences in repair capacity between individuals have been widely documented. 
For colorectal cancer, the loss of mismatch repair gene activity is a key 
genetic determinant. Nucleotide excision repair (NER), recombination repair (RR) 
and base excision repair (BER) pathways have critical roles in protection 
against other cancers, and we wished to investigate their role in colorectal 
cancer. We have compared the frequency of polymorphisms in the NER genes, XPD, 
XPF, XPG, ERCC1; in the BER gene, XRCC1; and in the RR gene, XRCC3; in 
colorectal cancer patients and in a control group. No significant associations 
were found for any of the NER gene polymorphisms or for the XRCC1 polymorphism. 
The C allele (position 18067) of the XRCC3 gene was weakly but significantly 
associated with colorectal cancer (odds ratio 1.52, 95% confidence interval 
1.04-2.22, P=0.03). For all patients who were heterozygous for any of the repair 
genes studied, tumour tissue was investigated for loss of heterozygosity (LOH). 
Only one example of LOH was found for all the genes examined. From the 
association and LOH data, we conclude that these genes do not have an important 
role in protection against colorectal carcinogenesis.