For a study, the researchers sought to create and evaluate a nomogram that could predict overall survival (OS) for patients with early-stage non-small cell lung cancer (NSCLC) who were treated with stereotactic ablative radiotherapy (SABR) vs observation. Adults with biopsy-proven T1-T2N0 NCSLC who were treated with SABR (30-70 Gy in 1-10 fractions with physiologically effective dose ≥100 Gy10) or observed in the National Cancer Database (NCDB) between 2004 and 2015 were identified. On predictive demographic and clinicopathologic characteristics found by logistic regression, the propensity score was utilized to link SABR and observation cohorts. A multivariable Cox proportional hazard was discovered using backward selection and a nomogram to predict 2- and 5-year OS. Time-dependent receiver operating characteristic (ROC) curves and integrated area under the ROC curve (AUC) analysis were used to measure model prediction accuracy. A total of 22,073 people satisfied the criterion for inclusion, and 4,418 matched pairs (n=8,836) were selected for nomogram construction. On multivariable analysis, younger age (HR 0.82 by decade, P<.001), female sex (HR 0.81, P<.001), lower comorbidity index (HR 0.65 for 0 vs ≥3, P<.001), smaller tumor size (HR 0.60 for ≤3cm vs 5.1-7cm, P<.001), adenocarcinoma histology (P<.001), and receipt of SABR (P<.001) were the factors most strongly associated with improved OS. The interaction of SABR and histology was substantially related to OS (P=.017). Patients with squamous cell carcinoma observed (HR 1.44, 95% CI 1.33-1.56) or treated with SABR (HR 1.24, 95% CI 1.14-1.35) had significantly lower OS than patients with adenocarcinoma. The nomogram showed fair accuracy in predicting OS with an integrated time-dependent AUC of 0.694 across the whole follow-up period. Whether medically inoperable early-stage NSCLC patients received SABR or prefer observation, the nomogram estimates OS at 2 and 5 years. Other variables not included in the NCDB could help increase the model’s accuracy.