Association between XPD Lys751Gln polymorphism and bladder cancer susceptibility: an updated and cumulative meta-analysis based on 6,836 cases and 8,251 controls

The association between xeroderma pigmentosum group D (XPD) Lys751Gln polymorphism and bladder cancer (BC) susceptibility was investigated by two meta-analyses, however, their results were contrary. We conjecture the reason might be the sample size, thus we performed this updated and cumulative meta-analysis using the Comprehensive Meta-Analysis software. We searched PubMed up to August 25th, 2013 and yielded 20 published articles with 21 case–control trails including 6,836 BC patients and 8,251 controls. The meta-analysis results showed that XPD Lys751Gln polymorphism was borderline significantly associated with BC susceptibility for overall population [Gln vs. Lys: OR 1.07, 95 % CI 1.01–1.12, P = 0.01; Gln/Gln vs. Lys/Lys: OR 1.15, 95 % CI 1.03–1.29, P = 0.01; Gln/Gln vs. (Lys/Gln + Lys/Lys): OR 1.13, 95 % CI 1.02–1.26, P = 0.02]. The cumulative meta-analysis according to the publication year showed the CI became increasingly narrower and tended to have statistical significance for the studies incessantly accumulated. In the subgroup analysis according to ethnicity, there was a significant association in Asian population and no association in Caucasian population. There was no publication bias detected. However, due to the limitations and cumulative analysis result of this meta-analysis, more well-designed and larger studies with risk factors adjusted are suggested to be performed to obtain a conclusive result on this topic.