PPARG and rectal cancer: PPARG rs1801282 C>G polymorphism was associated with decreased risk of colon cancer (G vs. C: OR = 0.66, 95% CI = 0.48–0.90, P = 0.009, GG+CG vs. CC: OR = 0.82, 95% CI = 0.71–0.94, P = 0.004, CG vs. CC + GG: OR = 0.70, 95% CI = 0.50–0.98, P = 0.035 and CG vs. CC: OR = 0.69, 95% CI = 0.49–0.96, P = 0.029; Supplementary Table 1), and rectum cancer (G vs. C: OR = 0.77, 95% CI = 0.59–0.99, P = 0.042, CG vs. CC + GG: OR = 0.73, 95% CI = 0.55–0.97, P = 0.032 and CG vs. CC: OR = 0.73, 95% CI = 0.55–0.97, P = 0.032; Supplementary Table 1), but not mixed type of CRC.