MGMT and neoplasm: First, the SEER database lacks important prognostic variables such as performance status (e.g., Karnofsky Performance Status), comorbidity indices (e.g., Charlson Comorbidity Index), tumor location, underlying diseases (e.g., coronary heart disease), smoking and alcohol consumption status, and tumor molecular markers (e.g., IDH mutation status, MGMT promoter methylation).