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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 (suvmax), 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, suvmax 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, suvmax, 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 suvmax, 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.