Summary ORs (95% CI) for the XRCC1 Arg399Gln polymorphism categorized by histological type or anatomical area in a specific tumor site1.

1all summary ORs were calculated using fixed-effects models. In the case of significant heterogeneity (indicated by *), ORs were calculated using random-effects models;2the results were excluded due to high heterogeneity;3includes a diversity of head and neck cancer not separated by anatomical area in the studies analyzed;4means adenocarcinoma’.5means squamous cell carcinoma;6small cell lung cancer; the bold values indicate that the results are statistically significant.