A meta-analysis combining 20 studies (including 1539 NSCLC patient tissues and 1052 normal or adjacent tissue samples) proposes that: 1) the MGMT promoter methylation level in NSCLC tissues is much higher than that in normal tissue samples, and MGMT methylation is not related to clinical pathological characteristics such as age, gender, smoking and pathological type; 2) MGMT promoter methylation level in tissues from NSCLC patients was higher in late stage (III and IV) than in early stage (I and II) (41). The gene discussed is MGMT; the disease is non-small cell lung carcinoma.