Bad LAD.

Top Line: Does mean heart dose adequately predict the risk of adverse events associated with cardiac sub-structures?

The Study: A recent analysis of cardiac dose in >700 patients receiving thoracic radiation for NSCLC found a significant increase in the risk of major adverse cardiac events (MACE) when the left anterior descending artery (LAD) V15 was 10% or higher. While the paper described optimal dosimetric thresholds for other cardiac sub-structures, LAD V15 was independently associated with the risk of MACE. This follow-up analysis from the same group sought to determine if mean heart dose (MHD) is a good surrogate for LAD V15--because let’s be honest, there are fewer residents in the pipeline to contour cardiac sub-structures. Patients were categorized as having 1) high MHD (>10 Gy) and high LAD V15 (>10%), 2) high MHD, low LAD V15, 3) low MHD, high LAD V15, and 4) low MHD, low LAD V15. Most patients had concordant high/high (44%) or low/low (33%) dosimetry while 14% had high MHD/low V15 and 9% had low MHD/high V15. Patients with a low LAD V15 had significantly lower risk of MACE than those with high LAD V15--regardless of whether they had a high or low MHD. Put another way, patients with a low MHD but a high LAD V15 had a higher risk of MACE at 2-years (13%) than those with a high MHD but low LAD V15 (4.2%).

TBL: The left anterior descending artery V15 +/- 10% is associated with MACE risk after thoracic radiation, and mean heart dose is a poor surrogate for LAD V15. | Atkins, Int J Radiat Oncol Biol Phys 2021