Changes in cardiac function in patients receiving radiation therapy for lung cancer

Introduction
The cardiovascular toxicity of radiation therapy (RT) remains incompletely understood in patients with non-small cell lung cancer (NSCLC). Our objective was to define changes in echocardiographic parameters of structure and function with RT and their associations with cardiac dose-volume metrics.
Methods
This multi-center, longitudinal prospective cohort study included participants with NSCLC who received standard, curative-intent thoracic RT. Dose-volume metrics were extracted from centrally contoured cardiac substructures. Echocardiograms at baseline, end of RT, six months post-RT, and 12 months post-RT were core lab-quantified. Repeated-measures multivariable linear regression via generalized estimating equations estimated changes in echocardiographic measures and associations with dose-volume metrics.
Results
Across 125 participants, there was a modest worsening in left ventricular ejection fraction (LVEF) (p=0.019), global longitudinal strain (p<0.001), circumferential strain (p<0.001), and Ea/Ees (p=0.011) post-RT that largely recovered by 12 months. Cardiac dysfunction, defined as LVEF declines of ≥10% to <50%, occurred in 7.2% of participants at a median of 1.7 months after RT initiation. Mean heart dose (MHD) was associated with LVEF declines (-1.1%, 95% confidence interval (CI) [-2.2,0.0] per interquartile range (IQR) increase, p=0.044), as was whole heart V30 (-1.4%, 95%CI[-2.5,-0.3] per IQR increase, p=0.015); with multiple comparisons adjustment, whole heart V30 remained significant (p=0.030).
Conclusions
On average, there were modest changes in cardiac function immediately after RT in patients with NSCLC, with a subset experiencing clinically relevant cardiac dysfunction. While whole heart V30 was associated with LVEF declines, suggesting its relevance in RT planning, there is also a need for newer dose-volume measures