Tracking Changes in Global Longitudinal Strain in Lung Cancer Patients Receiving Thoracic Radiation

Abstract

Thoracic radiation improves survival in many lung cancer patients. However, radiation-induced cardiotoxicity is a major source of morbidity and mortality in such patients. Global longitudinal strain (GLS), a novel echocardiography (ECHO) method of assessing left ventricular function, has been shown to predict long-term adverse cardiovascular risk in diverse patient populations. We hypothesized that receipt of thoracic radiation is associated with GLS changes in lung cancer patients. We retrospectively identified patients with lung cancer treated at our institution between 2005-2020 who had ECHOs performed both before and after RT, and in whom GLS was extractable. ECHO Board-Certified cardio-oncologists measured GLS and left ventricular ejection fraction (LVEF) from these ECHOs. A total of 40 patients met inclusion criteria. Median time to ECHO was 78 days prior and 172 days after RT. Two chamber (2C), 3C, 4C, and average GLS were significantly decreased after RT on paired t-test [mean difference (SD) 2.23 (3.29), 2.99 (2.78), 2.25 (3.63), 2.51 (2.66) respectively, all p < 0.001]. Thirteen patients (32.5%) had abnormal GLS (<18%) prior to RT. 5 of those 13 patients (38.5%) had abnormal LVEF (< 50%). 27/40 patients (67.5%) had an abnormal GLS or clinically significant (≥15%) drop in GLS after RT. This difference (32.5% patients pre-RT vs 67.5% post-RT) was statistically significant (p < 0.01). Among patients (n = 27) who had normal LVEF before RT, 1 patient (3.7%) developed abnormal LVEF (<50%) after RT. Backwards logistic regression showed significant interaction between heart volume receiving 5 Gray and change in GLS. This cohort exhibited a significant decrease in 2C, 3C, 4C, and average GLS after RT. ∼1/3 of patients had abnormal GLS at baseline (suggesting a high-risk group for cardiac complications) and 67.5% of patients had clinically significant decrease in GLS after RT. Among the patients with normal GLS before RT, although 51.9% of patients demonstrated a clinically significant drop in GLS after RT, only 3.7% of patients developed abnormal LVEF, suggesting that this is a late occurrence. GLS changes may serve as a valuable tool for early identification of patients who are at high risk for future cardiac complications after receiving thoracic radiation.