Utilizing FDG-PET/CT to Assess Radiation-induced Cardiotoxicity in Patients with Lung Cancer Based on Tumor Location

Objectives: Radiation therapy (RT) has been established as a highly effective treatment for locally advanced lung cancer. However, radiation-related cardiotoxicity is a risk associated with chest RT that can limit the utilization of RT. Several studies have shown increases in cardiovascular injury and mortality with increasing doses of RT in patients with lung cancer. However, the risk of cardiotoxicity based on the site of the lung tumor has been studied to a lesser extent. FDG-PET/CT, with its unique capability to detect metabolic activity of various tissues, can be utilized to identify post-RT cardiac injury in subclinical and clinical stages. In this study, we aimed to evaluate RT-related cardiotoxicity in lung cancer patients based on tumor location by analyzing FDG PET/CT images pre- and post-RT. Methods: We evaluated 65 patients with inoperable stage II and stage III non-small cell lung cancer (NSCLC) with no distant metastasis (American College of Radiology Imaging Network (ACRIN); NCT00083083). The patients received daily thoracic RT of 1.8-2.0 Gy, up to a total dose of at least 60 Gy, with concurrent platinum-based doublet chemotherapy. FDG-PET/CT scans were performed before and 5-6 months after RT. Images were analyzed by OsiriX MD software (Pixmeo SARL, Bernex, Switzerland). The regions of interests were placed on all the axial slices of the heart from the base to the apex. The global cardiac mean standardized uptake volume (GC SUVmean) was calculated as the weighted average of SUVmean using axial images surface area. The GC SUVmean were analyzed based on the site of lung lesions: the upper half of the right lung, the lower half of the right lung, the upper half of the left lung and the lower half of the left lung.

Results: The GC SUVmean was increased significantly following RT in patients with left lung lesions (51.27% increase in lower left lung lesions with P-value=0.002, and 25.01% increase in upper left lung lesions with P-value=0.02). However, there was no significant change in GC SUVmean in those with right lung lesions. Conclusions: The average increase in the GC SUVmean in patients with left lower lung lesions was significantly greater than that in patients with left upper or right lung lesions. Therefore, in our study, the most radiation-induced cardiotoxicity was seen in patients with left lower lung lesions. These findings may be useful to consider in RT treatment planning, and also suggest the need for closer cardiac monitoring post-RT in this group of patients.