MGMT and head and neck squamous cell carcinoma: For all three patient datasets, a variety of potential cofounding variables was included during multivariable Cox regression analysis, including patient age, radiotherapy prescription dose, smoking history, and the inclusion of additional treatments like surgery or chemotherapy (both for HNSCC and NSCLC), staging (for HNSCC), histology (for NSCLC), and IDH1/2 and MGMT status (for GBM).