Metabolic Tumour Volume Is Prognostic in Patients with Non-Small-Cell Lung Cancer Treated with Stereotactic Ablative Radiotherapy

Introduction: Stereotactic ablative radiotherapy (SABR) is a relatively new technique for the curative-intent treatment of patients with inoperable early-stage non-small-cell lung cancer (NSCLC). Previous studies have demonstrated a prognostic value for positron emission tomography–computed tomography (PET/CT) parameters, including maximal standardized uptake value (SUV_max), metabolic tumour volume (MTV), and total lesion glycolysis (TLG) in lung cancer patients. We aimed to determine which pet/ct parameter is most prognostic of local control (LC) and overall survival (OS) in patients treated with SABR for NSCLC. Methods: We conducted a retrospective review of patients treated with SABR for stage i inoperable NSCLC at BC Cancer between 2009 and 2013. The Akaike information criterion was used to compare the prognostic value of the various PET/CT parameters. Results: The study included 134 patients with a median age of 76 years. Median tumour diameter was 2.2 cm, gross tumour volume was 8.1 mL, SUV_max was 7.9, MTV was 2.4 mL, and tlg was 10.9 SUV•mL. The 2-year LC was 92%, and os was 66%. On univariate and multivariate analysis, imaging variables including tumour size, gross tumour volume, SUV_max, MTV, and tlg were all associated with worse LC. Tumour size was not associated with significantly worse OS, but other imaging variables were. The PET/CT parameter most prognostic of LC was MTV. Compared with SUV_max, TLG and MTV were more prognostic of OS. Conclusions: In patients with early-stage NSCLC treated with SABR, MTV appears to be prognostic of LC and OS.