Confounding and Mediation

Surgery may provide an advantage because invasive lymph node staging can reveal nodal metastasis and enable adjuvant chemotherapy. Baseline confounders include age, comorbidities, lung function, performance status, hospital volume, and socioeconomic deprivation. DAGitty identified the same variables as the minimal sufficient adjustment set. A directed acyclic graph was used to identify confounders and mediators between treatment and survival. Adjuvant treatment and postoperative toxicities are treated as mediators because they occur after treatment selection and may affect survival.