A meta-analysis of 20 case-control studies of the glutathione S-transferase M1 (GSTM1) status and colorectal cancer risk.

BACKGROUND: Glutathione S-transferase M1 is an important phase II enzyme involved in the detoxification of many environmental carcinogens. It has been postulated that individuals with GSTM1 deficiency have increased susceptibility to carcinogens and are more likely to develop cancer. GSTM1 status has been extensively studied as a colon cancer risk factor, although published studies have produced conflicting results. To re-examine this controversy, we have undertaken a meta-analysis investigating the relationship of GSTM1 status and colon cancer risk. MATERIAL/
METHODS: Odds ratio was employed to evaluate the risk of colon cancer and GSTM1 status. To take into account the possibility of heterogeneity across the studies, a statistical test for heterogeneity across the studies was performed. The summary odds ratios were assessed by calculating a weighted average of odds ratios for all of the studies.
RESULTS: The pooled odds ratio of colon cancer risk associated with the GSTM1 deficiency is 0.99 (95% CI: 0.91-1.07). If pooling studies were based on the genotyping method, the overall odds ratio of colon cancer risk associated with the GSTM1 deficiency showed no difference. Moreover, the relationship of GSTM1 deficiency and colon cancer risk was also conducted on the specific ethnic groups and tumour site.
CONCLUSIONS: The results of our meta-analysis does not support the hypothesis that GSTM1 alone is an important risk factor for colon cancer, and suggests that GSTM1 status has no effect on the risk of developing colon cancer.