Association between the COMT Val158Met polymorphism and breast cancer risk: a meta-analysis of 30,199 cases and 38,922 controls.

Many studies have reported the role of COMT Val158Met with breast cancer risk, but the results remained controversial. In addition, previous meta-analysis on COMT Val158Met showed conflicting results. Hence, we performed a meta-analysis to investigate the association between breast cancer and COMT Val158Met (30,199 cases and 38,922 controls) in different inheritance models. When all the eligible studies were pooled into this meta-analysis, there was no evidence of significant association between breast cancer risk and COMT Val158Met polymorphism in any genetic model (dominant model: odds ratio [OR] = 0.99, 95% confidence interval [CI] = 0.94-1.04, P value of heterogeneity test [P(h)] = 0.009, I(2) = 36.9%; recessive model: OR = 0.97, 95% CI = 0.92-1.02, P(h) = 0.044, I(2) = 28.6%; additive model: OR = 0.98, 95% CI = 0.91-1.05, P(h) = 0.004, I(2) = 40.4%). However, significant between-study heterogeneity was detected in any genetic model. Hence, we performed the stratified analysis according to ethnicity, source of controls, menopausal status, and family history. In the stratified analysis by ethnicity significantly decreased breast cancer risk was observed in Caucasian population (recessive model: OR = 0.96, 95% CI = 0.92-1.00, P(h) = 0.419, I(2) = 3.1%). In conclusion, this meta-analysis indicates that COMT Val158Met polymorphism may be associated with decreased breast cancer risk in Caucasian population. However, a study with the larger sample size is needed to further evaluated gene-environment interaction on COMT Val158Met polymorphisms and breast cancer risk.