As a finding of benign disease is uncommon in Dutch patients undergoing surgery after a clinical diagnosis of stage I NSCLC, patients are also accepted for stereotactic ablative radiotherapy (SABR) without pathology. We studied outcomes in patients who underwent SABR after either a pathological (n=209) or clinical diagnosis (N=382).

Five hundred and ninety-one patients with a single pulmonary lesion underwent SABR after either a pathological- or a clinical diagnosis of stage I NSCLC based on a (18)FDG-PET positive lesion with CT features of malignancy. SABR was delivered to a total dose of 60Gy in 3, 5 or 8 fractions, and outcomes were compared between groups with and without pathological diagnosis.

Patients with pathology had significantly larger tumor diameters (p<.001) and higher predicted FEV1% values (p=.025). No significant differences were observed between both groups in overall survival (p=.99) or local control (p=.98). Regional and distant recurrence rates were also similar.

In a population with a low incidence of benign (18)FDG-PET positive lung nodules, clinical SABR outcomes were similar in large groups of patients with or without pathology. The survival benefits reported after the introduction of SABR are unlikely to be biased by inclusion of benign lesions.