The associations seem to be also relevant to the conflicting results reported in studies that correlated GSTM1 with risk of cancer and other diseases [6, 20–24] in which the absence of GSTM1-related enzymatic activity could be masked by catalytic activities of other GSTMs and resulted in no or reduced impact of GSTM1 deletion on disease risk. This evidence concerns the gene GSTM1 and cancer.