A prospective study of Gallium-68 ventilation and perfusion PET/CT during and after radiotherapy in patients with non-small cell lung cancer.

Abstract

To utilize ⁶⁸Gallium (Ga) Ventilation-Perfusion (V/Q) 4-dimensional (4D) PET/CT to establish the impact of curative radiotherapy (RT) doses on lung ventilation and perfusion, and to evaluate associations with clinical outcomes. This prospective non-randomized observational clinical trial included 67 patients undergoing definitive RT +/-chemotherapy for NSCLC. Patients underwent ⁶⁸Ga 4D V/Q PET/CT at baseline, mid-treatment, and at 3- and 12-months post-treatment. Pulmonary Function Tests (PFTs) and toxicities were assessed at baseline and 3 monthly after treatment. Linear mixed models were used to assess for associations between radiotherapy dose-volume, applied to ventilated and perfused lung at 5 %, 30 % and 70 % thresholds as defined by ⁶⁸Ga 4D V/Q PET/CT, and toxicity. Sixty-seven patients were evaluable, of whom 44 (66 %) were male, mean age was 68, and 61 (91 %) were ECOG 0-1. Sixty-three patients completed treatment and grade ≥2 pneumonitis occurred in 20 (32 %). Lung ventilation and perfusion, and FEV1 and DLCO, fell slightly from baseline to 3-months post treatment. V54 Gy of perfused lung at the 30 % threshold was higher in those with grade ≥2 pneumonitis (median 12.9 % (IQR 8.7-14.8 %) vs 6.3 % (IQR 3.7-8.5 %), p = 0.003). No association between grade ≥2 pneumonitis and the absolute change in ventilated (p = 0.12) or perfused (p = 0.14) lung was observed. We observed a decrease in lung ventilation and perfusion on ⁶⁸Ga 4D V/Q PET/CT from baseline to 3 months after RT. The association between the volume of well-perfused lung receiving near-therapeutic RT doses and the development of grade ≥2 pneumonitis warrants future investigation.