Top Line: RTOG 0617 reminded us there is a fine balance between increasing tumor control at the expense of increasing treatment toxicity.
The Study: Team cardiac substructures is back at it with a dosimetric analysis of 0617 enrollees aimed at investigating whether dose to varying parts of the heart cause varying degrees of havoc. It employed an interesting voxel-based analysis of plans from 458 enrollees, free from any assumptions of how to best categorize cardiac subregions based on prior investigations. The result was that radiation dose specifically to a region at the base of the heart, in the vicinity of the origin of the left coronary artery and the sinoatrial node, was significantly associated with survival on extensive multivariable analysis including total heart dosimetry. In fact, when accounting for dose to this specific region, total heart dosimetry was no longer a significant factor. If this sounds familiar, it’s because the same group reported very similar findings a few months back using data from another trial (PET-Plan). The voxel based analysis used in the current and prior study does not rely on contouring cardiac substructures. Thus, the agreement between studies in identifying the subregion at the base of the heart in the vicinity of the LAD and SA node likely means dose to this area has important effects on cardiac toxicity. Unfortunately, we don’t exactly know what dose constraint to this region may reduce cardiac risk. As a reference, though, the median Dmean to this subregion was 9.1 Gy in the low dose arm of 0617 and 10.2 Gy in the high dose arm.
TBL:A specific region at the base of the heart appears particularly sensitive to radiation and may provide an achievable avoidance region to diminish radiation cardiotoxicity. | McWilliam, J Thorac Oncol 2023
The Study: Team cardiac substructures is back at it with a dosimetric analysis of 0617 enrollees aimed at investigating whether dose to varying parts of the heart cause varying degrees of havoc. It employed an interesting voxel-based analysis of plans from 458 enrollees, free from any assumptions of how to best categorize cardiac subregions based on prior investigations. The result was that radiation dose specifically to a region at the base of the heart, in the vicinity of the origin of the left coronary artery and the sinoatrial node, was significantly associated with survival on extensive multivariable analysis including total heart dosimetry. In fact, when accounting for dose to this specific region, total heart dosimetry was no longer a significant factor. If this sounds familiar, it’s because the same group reported very similar findings a few months back using data from another trial (PET-Plan). The voxel based analysis used in the current and prior study does not rely on contouring cardiac substructures. Thus, the agreement between studies in identifying the subregion at the base of the heart in the vicinity of the LAD and SA node likely means dose to this area has important effects on cardiac toxicity. Unfortunately, we don’t exactly know what dose constraint to this region may reduce cardiac risk. As a reference, though, the median Dmean to this subregion was 9.1 Gy in the low dose arm of 0617 and 10.2 Gy in the high dose arm.
TBL:A specific region at the base of the heart appears particularly sensitive to radiation and may provide an achievable avoidance region to diminish radiation cardiotoxicity. | McWilliam, J Thorac Oncol 2023