BACKGROUND: Stereotactic body radiation therapy (SBRT) is used to treat stage I non-small cell lung cancer (NSCLC) in nonsurgical candidates, although guidelines specify that inoperability be determined in multidisciplinary fashion. We characterized NSCLC patients treated with SBRT undergoing thoracic surgical evaluation (TSUe) and quantified TSUe's impact on time to treatment, receipt of diagnostic staging procedures, and health care costs. METHODS: Adults with newly diagnosed NSCLC undergoing SBRT were identified in the MarketScan all-payer claims database (2014-2018). TSUe was defined as an outpatient encounter with a thoracic surgeon or multispecialty group. Time to treatment and total costs in the 6 months preceding treatment were examined using multivariable regression by receipt of TSUe, adjusting for demographic and clinical factors. RESULTS: Of 1894 patients, 36.3% (n = 687) underwent TSUe. Compared with patients without TSUe, these patients were younger (mean age, 73.6 vs 76.3 years) and more likely to undergo invasive biopsy/staging procedures (90% vs 82%) or pulmonary function testing (80.6% vs 69.5%). Patients undergoing TSUe had a median time to treatment of 64 days (interquartile range, 43-98 days), compared with 44 days (interquartile range, 29-70 days) for no TSUe. Adjusted time to treatment was 43% longer (incident rate ratio, 1.43; 95% CI, 1.32-1.54; P < .001) with TSUe. Patients undergoing TSUe also incurred 30% higher costs (adjusted cost ratio, 1.30; 95% CI, 1.20-1.41; P < .001). CONCLUSIONS: Among patients with early-stage NSCLC undergoing SBRT as primary treatment, a minority are evaluated by a thoracic surgeon. Because they have a longer time to treatment, more invasive diagnostic procedures, and higher costs, this represents a targetable gap to make workup protocols more efficient.