Int J Radiat Oncol Biol Phys. 2023 Oct 22:S0360-3016(23)08008-2. doi: 10.1016/j.ijrobp.2023.10.004. Online ahead of print.
PURPOSE: To compare anatomical and functional dose-volume parameters as predictors of acute radiation-induced lung toxicity (RILT) in patients with lung tumors treated with stereotactic body radiation therapy (SBRT).
MATERIALS AND METHODS: 59 patients treated with SBRT were prospectively included. All patients underwent Gallium-68 lung perfusion PET/CT imaging before treatment. Mean lung dose (MLD) and volumes receiving xGy (VxGy, 5 to 30 Gy) were calculated in five lung volumes: the conventional anatomical volume (AV) delineated on CT images, three lung functional volumes defined on lung perfusion PET imaging (FV50%, FV70%, FV90%, i.e. the minimal volume containing 50%, 70% and 90% of the total activity within the AV), and a low functional volume (LFV = AV-FV90%). The primary endpoint of this analysis was grade ≥2 acute RILT at 3 months as assessed with NCI CTCAE v.5. Dose volume parameters in patients with and without acute RILT were compared. ROC curves assessing the ability of dose-volume parameters to discriminate between patients with and without acute RILT were generated and area under the curves (AUC) were calculated.
RESULTS: Out of the 59 patients, 10 (17%) had grade ≥2 acute RILT. The MLD and the VxGy in the AV and LFV were not statistically different in patients with and without acute RILT (p>0.05). All functional parameters were significantly higher in acute RILT patients (p<0.05). AUCs (CI 95%) for MLD AV, LFV, FV50%, FV70% and FV90% were 0.66 (0.46-0.85), 0.60 (0.39-0.80), 0.77 (0.63-0.91), 0.77 (0.64-0.91), 0.75 (0.58-0.91), respectively. AUCs for V20Gy AV, LFV, FV50%, FV70% and FV90% were 0.65 (0.44-0.87), 0.64 (0.46-0.83), 0.82 (0.69-0.95), 0.81 (0.67-0.96), 0.75 (0.57-0.94), respectively.
CONCLUSION: The predictive value of PET perfusion-based functional parameters outperforms the standard CT-based dose-volume parameters for the risk of grade ≥2 acute RILT. Functional parameters could be useful to guide radiotherapy planning to reduce the risk of acute RILT.