Association between two polymorphisms of ABCB1 and breast cancer risk in the current studies: a meta-analysis

Previous epidemiological studies have evaluated the association between the ABCB1 polymorphism and the risk of breast cancer with conflicting results. Hence, we conducted a meta-analysis of the ABCB1 gene and risk of breast cancer to obtain the most reliable estimate of the association. PubMed, Embase, and Web of Science databases were searched. A total of eight studies including 3,829 cases and 6,193 controls were identified. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were extracted and pooled to assess the strength of associations between the ABCB1 C3435T and rs2214102 G>A polymorphisms and risk of breast cancer. Of these studies, only one deviated from Hardy-Weinberg equilibrium. Summary estimates indicated that the ABCB1 C3435T polymorphism was not associated with increased risk of breast cancer in the allele contrast model (T vs. C, pooled OR = 1.15; 95% CI = 0.89-1.48); the co-dominant model (CT vs. CC, OR = 1.12 [0.86-1.46] and TT vs. CC, OR = 1.30 [0.79-2.15]); the dominant model (OR = 0.80 [0.63-1.02]; and the recessive model (OR = 0.83 [0.57-1.22]). In the sensitivity analysis by ethnicity, no statistically significant associations were detected in Asians. However, in Caucasian women the T allele contrast model and the TT genotype were each associated with increased risk: T vs. C, pooled OR (95% CI) = 1.26 (1.04-1.52) and TT vs. CC, OR = 1.48 (1.04-2.11). Accordingly, the dominant model yielded statistically significant results (pooled OR = 0.71, 95% CI: 0.52-0.96) but not with the allele contrast model or the co-dominant model. There was evidence of publication bias (P = 0.02 for recessive model). In conclusion, there is limited evidence to indicate that the ABCB1 C3435T and rs2214102 G>A polymorphisms are associated with increased risk of breast cancer.