Differential effects of insulin-like growth factor-1 CA repeat polymorphism on breast cancer risk along with race: a meta-analysis.

BACKGROUND

Insulin-like growth factor (IGF)-I has been implicated in processes leading to breast cancer initiation and progression. A CA repeat polymorphism in the promoter region of IGF-I may suppress transcriptional activity and be associated with risk of breast cancer. A variety of case-control studies have been published evaluating the association between IGF1 CA repeat polymorphism and breast cancer. However, those published studies yielded contradictory conclusions.

RESULTS

This meta-analysis enrolled eleven studies to estimate the overall breast cancer risk of IGF1 CA repeat polymorphism. There was no significantly breast cancer risk found for pooled ORs among all the models. In the sub-stratified analysis by ethnicity, significantly decreased risks were found among Caucasian (19/19 versus non19/non19: OR=0.81, 95% CI: 0.70-0.94, P=0.922; 19/non19 versus non19/non19: OR=0.86, 95% CI: 0.74-0.99, P=0.005; dominant model: OR=0.84, 95% CI: 0.73-0.96, P=0.871). However, no significantly breast cancer risk was found among Asian and other ethnicities for all the genetic models. Furthermore, in the menopausal status stratified analysis, a significant decreased risk for postmenopausal woman was observed in the comparison of genotype 19/19 versus 19/non19+non19/non19: OR=0.89, 95% CI: 0.81-0.99, P=0.603. In addition, in the stratified analysis by case size, significantly decreased risk was observed in studies whose case size was more than 500 (19/19 versus 19/non19+non19/non19: OR=0.92, 95% CI: 0.86-1.00, P=0.457).

CONCLUSIONS

This study suggested that genotype 19/19 of IGF1 CA repeat polymorphism is a decreased risk for developing breast cancer in Caucasian but not in Asian, indicating that the association might be adjusted by race.