Top Line: How can we do a better job of reducing lung and heart dose during treatment of locally advanced NSCLC?
The Studies: Here are two studies investigating strategies to better optimize lung and heart dosimetry when treatment LA-NSCLC. This phase 2 study sought to determine the feasibility of treatment plan optimization to reduce dose to functional lung volume. They used standard treatment planning 4D-CT to contour the lung volume at end-inspiration and end-expiration. Deformable image registration was used to link voxels between image sets. The change in voxel density between phases was used to model ventilatory function. Standard treatment plans were generated for 67 patients and then further optimized to reduce dose to functional lung without sacrificing target coverage or other OAR constraints. Functional lung optimization, on average, reduced functional mean lung dose by 1.3 Gy and V20 by 3.5%. The rate of grade 2+ RP was 14.9%, but this study doesn’t tell us yet if the technologically intensive technique of 4D-CT ventilation avoidance reduces RP risk. A practical challenge in reducing lung dose is the tradeoff with heart dose. Separately, this study used machine learning to analyze treatment plans from >350 patients to show that in many plans (40% overall, 73% if changed to IMRT) could meaningfully reduce heart dose without exceeding lung constraints. For example, a reduction in mean heart dose of 3.7-4.3Gy could be achieved with a tradeoff increase of 3.3% for V20, 5% for V5, and 1Gy for mean lung dose.
TBL: Many treatment plans for LA-NSCLC could benefit from additional optimization efforts to better spare functional lung tissue or the heart without significantly changing dose to other organs at risk. | Vinogradskiy, Int J Radiat Oncol Biol Phys 2021 & Bitterman, Int J Radiat Oncol Biol Phys 2021