GSTM1 and colorectal carcinoma: First, the sample size was much larger, with 86 case–control studies including 24,931 CRC cases and 36,537 controls evaluated for the GSTM1 present/null polymorphism, 64 case–control studies including 19,725 CRC cases and 28,725 controls for the GSTT1 present/null polymorphism, and 33 case-control studies including 8306 CRC cases and 14,369 controls for their combined effects in all races.