MTHFR and non-small cell lung carcinoma: After adjustment by logistic regression analysis, we found MTHFR rs1801133 G>A variants were associated with the decreased risk of NSCLC in some subgroups (female group: AA vs. GG: adjusted OR = 0.53, 95% CI 0.30–0.94, P = 0.031 and AA vs. GA/GG: adjusted OR = 0.58, 95% CI 0.33–1.00, P = 0.048; < 60 years subgroup: AA vs. GG: adjusted OR = 0.53, 95% CI 0.28–1.00, P = 0.048; never smoking group: AA vs. GG: adjusted OR = 0.58, 95% CI 0.36–0.93, P = 0.024 and AA vs. GA/GG: adjusted OR = 0.62, 95% CI 0.39–0.99, P = 0.044; Table 4).