Mean Heart Dose is an Inadequate Surrogate for Left Anterior Descending Coronary Artery Dose and the Risk of Major Adverse Cardiac Events in Lung Cancer Radiotherapy

ABSTRACT Purpose Mean heart dose (MHD) over 10 Gy and left anterior descending (LAD) coronary artery volume (V) receiving 15 Gy (V15Gy) greater than 10% can significantly increase the risk of major adverse cardiac events (MACE) in patients with non-small cell lung cancer (NSCLC). We sought to characterize the discordance between MHD and LAD dose and the association of this classification on the risk of MACE following radiotherapy. Materials and Methods Retrospective analysis of 701 patients with locally advanced NSCLC treated with radiotherapy. Coefficient of determination for MHD and LAD V15Gy was calculated. Four groups were defined based on high or low MHD (≥10 Gy vs. Results The proportion of variance in LAD V15Gy predictable from MHD was only 54.5% (R2=0.545). There was discordance (where MHD was high [≥10 Gy] and LAD low [V15Gy Conclusions MHD is insufficient to predict LAD V15Gy with confidence. When MHD and LAD V15Gy dose exposure is discordant, isolated low LAD V15Gy significantly reduces the risk of MACE in patients with locally advanced NSCLC following radiotherapy, suggesting that the validity of whole heart metrics for optimally predicting cardiac events should be reassessed.