The association between IGF1 CA repeat polymorphisms and breast cancer risk: a meta-analysis

IGF-I CA repeat polymorphisms have been reported to influence the risk for breast cancer in many studies; however, the results still remains controversial and ambiguous. Therefore, to determine more precise estimations for the relationship, a meta-analysis was performed. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to estimate the strength of the association. A total of 9 studies including 5641 cases and 10471 controls were involved in this meta-analysis. All studies investigated the association between (CA)19 repeat polymorphism and breast cancer risk. Of those, four studies investigated the association between (CA)20 repeat polymorphism and breast cancer risk (2585 cases and 2847 controls), and three studies were for (CA)17 repeat polymorphism (2122 cases and 2225 controls). The overall odds ratio (OR) for the (CA)19 versus non-(CA)19 allele was 1.002 (95% CI 0.972-1.033). There was no suggestion of an overall effect either in recessive or dominant modeling of (CA)19 allele effects (dominant model: OR = 1.000 95% CI 0.872-1.147; recessive model: OR = 0.959 95% CI 0.888-1.036). The comparison of (CA)19 homozygosity versus non-(CA)19 homozygosity also showed no differential susceptibility to breast cancer (OR = 0.974, 95% CI 0.838-1.132). In the subgroup analysis by menopausal status, no statistically significantly increased risk was found among premenopausal or postmenopausal women. When stratified by ethnicity, no significant association was found in all genetic models. Furthermore, there was no evidence that two other alleles associated with the risk of breast cancer (CA17 vs. non-CA17: OR = 1.165 95% CI 0.634-2.141; CA20 vs. non-CA20: OR = 1.019 95% CI 0.909-1.143). In conclusion, the current meta-analysis suggests that three IGF-I (CA) repeat polymorphisms had no association to breast cancer risk.