METHODS: We systematically searched PubMed, Embase, Elsevier and Springer for relevant articles published before Nov 2011. Summary odds ratio (OR) and 95% confidence interval (95% CI) incidence rates were calculated using a random-effects model with STATA (version 10.0) software.
RESULTS: A total of fifteen case-control studies, including 19,621 cases and 27,001 controls based on the search criteria, were included for analysis. A significant association was found between carrying the CHEK2 I157T variant and increased risk of unselected breast cancer (OR = 1.48, 95% CI = 1.31-1.66, P < 0.0001), familial breast cancer (OR = 1.48, 95% CI = 1.16-1.89, P < 0.0001), and early-onset breast cancer (OR = 1.47, 95% CI = 1.29-1.66, P < 0.0001). We found an even stronger significant association between the CHEK2 I157T C variant and increased risk of lobular type breast tumors (OR = 4.17, 95% CI = 2.89-6.03, P < 0.0001).
CONCLUSIONS: Our research indicates that the CHEK2 I157T variant may be another important genetic mutation which increases risk of breast cancer, especially the lobular type.