Dose-Response Relationship Between Radiation Therapy and Loss of Lung Perfusion Comparing Positron Emission Tomography and Dual-Energy Computed Tomography in Non-Small Cell Lung Cancer

Abstract

Background: Radiotherapy treatment for non-small cell lung cancer (NSCLC) may result in radiation damage to the perfused lung. The loss in perfusion may be measured from positron tomography emission (PET) perfusion imaging, however, this modality may not be widely available. Dual-energy computed tomography (DECT) with contrast may be an alternative to PET/CT. The purpose of this work is to investigate the equivalence of dose-response curves (DRC) determined from PET and DECT in NSCLC. Methods: PET and DECT datasets from the prospective clinical trial BLINDED FOR REVIEW (BLINDED FOR REVIEW) were included in this pre-planned trial analysis. Patients underwent 68Ga-macroaggregated albumin (68Ga-MAA) PET/CT examination and DECT with contrast on the same day at baseline/3-months/12-months post-treatment. The perfused lung was defined from a threshold based on the maximum standardized uptake value (%SUVmax)/iodine concentration (%IoMax) in PET/DECT. The equivalence between PET and DECT DRC was established by comparing (1) the average of the normalized overlap of the two DRCs (aNO), ranging from 0 (no overlap) to 1 (perfect overlap), and (2) the slope of a linear model applied to DRCs. Results: Out of the 19 patients enrolled in the clinical trial, 14/10 patients had a post-treatment imaging session at median = 4.5 months/13.5 months, respectively. With 30%SUVmax/35%IoMax, aNO was maximized and the difference between PET and DECT slope of the linear model was minimized at each time point (slope = 0.76%/Gy / 0.75%/Gy at 3 months and 0.86%/Gy / 0.87%/Gy at 12 months determined from PET / DECT). Conclusions: Dose-response relationship determined from DECT was comparable to PET at 3- and 12-months post-treatment in NSCLC patients.