GSTM1 and chronic myelogenous leukemia, BCR-ABL1 positive: The findings showed that GSTM1null and GSTP1M*(AG/GG) together [GSTM1‐null/GSTP1M*(AG/GG)] and with GSTT1 present are associated with CML development and increased risk especially for GSTM1‐null/ GSTP1M* genotype is superadditive.