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T3801C is a common polymorphism in CYP1A1, showing differences in its biological functions. Case–control studies have been performed to elucidate the role of T3801C in cancer, although the results are conflicting and heterogeneous. Hence, we performed a meta-analysis to investigate the association between cancer susceptibility and T3801C (55,963 cases and 76,631 controls from 268 studies) polymorphism in different inheritance models. We used odds ratios with 95% confidence intervals to assess the strength of the association. Overall, significantly increased cancer risk was observed in any genetic model (dominant model: odds ratio [OR] = 1.14, 95% confidence interval [CI] = 1.09–1.19; recessive model: OR = 1.23, 95% CI = 1.12–1.34; CC vs. TT: OR = 1.31, 95% CI = 1.19–1.45; TC vs. TT: OR = 1.12, 95% CI = 1.07–1.18; additive model: OR = 1.14, 95% CI = 1.09–1.19) when all eligible studies were pooled into the meta-analysis. In further stratified and sensitivity analyses, the elevated risk remained for subgroups of cervical cancer, head and neck cancer, hepatocellular cancer, leukemia, lung cancer, prostate cancer and breast cancer. In addition, significantly decreased colorectal cancer risk was also observed. In summary, this meta-analysis suggests that the participation of CYP1A1 T3801C is a genetic susceptibility for some cancer types. Moreover, our work also points out the importance of new studies for T3801C association in some cancer types, such as gallbladder cancer, Asians of acute myeloid leukemia, and thyroid cancer, where at least some of the covariates responsible for heterogeneity could be controlled, to obtain a more conclusive understanding about the function of the CYP1A1 T3801C polymorphism in cancer development.

The T241M polymorphism in the X-ray cross-complementing group 3 (XRCC3) had been implicated in cancer susceptibility. The previous published data on the association between XRCC3 T241M polymorphism and cancer risk remained controversial. Hence, we performed a meta-analysis to investigate the association between cancer susceptibility and XRCC3 T241M (61,861 cases and 84,584 controls from 157 studies) polymorphism in different inheritance models. We used odds ratios with 95% confidence intervals to assess the strength of the association. Overall, significantly increased cancer risk was observed in any genetic model (dominant model: odds ration [OR]=1.07, 95% confidence interval [CI]=1.00-1.13; recessive model: OR=1.15, 95% CI=1.08-1.23; additive model: OR=1.17, 95% CI=1.08-1.28) when all eligible studies were pooled into the meta-analysis. In further stratified and sensitivity analyses, the elevated risk remained for subgroups of bladder cancer and breast cancer, especially in Caucasians. In addition, significantly decreased lung cancer risk was also observed. In summary, this meta-analysis suggests the participation of XRCC3 T241M in the susceptibility for bladder cancer and breast cancer, especially in Caucasians, and XRCC3 T241M polymorphism is associated with decreased lung cancer risk. Moreover, our work also points out the importance of new studies for T241M association in some cancer types, such as gastric cancer, colorectal cancer, and melanoma skin cancer, where at least some of the covariates responsible for heterogeneity could be controlled, to obtain a more conclusive understanding about the function of the XRCC3 polymorphism in cancer development.