MTHFR and lung carcinoma: Evidence from the pooled results indicated a significant association between the MTHFR C677T polymorphism and lung cancer susceptibility in Chinese people under the dominant, recessive, homozygous and allelic genetic models (T vs C: OR = 1.252, 95% CI, 1.090–1.437; TT vs CC: OR = 1.741, 95% CI, 1.252–2.420.