Assessing Acute Cardiac Inflammation One Month after Left-sided Breast Cancer Radiotherapy with Hybrid PET/MRI

Abstract Purpose: To investigate the utility of hybrid 18FDG-PET/MRI and serial blood work to detect early inflammatory response and cardiac functionality changes at one-month post-radiation therapy (RT) in patients with left-sided breast cancer.Methods: Fifteen left-sided breast cancer patients enrolled in the RICT-BREAST study underwent hybrid PET/MRI cardiac imaging at baseline and one-month after standard RT. Eleven patients received deep-inspiration breath-hold RT, while others received free-breathing RT. A list-mode 18FDG/PET scan with glucose suppression was acquired. Myocardial inflammation was quantified by the change of mean 18FDG standard uptake and analyzed based on the coronary vascular territory (left anterior descending (LAD), left circumflex or right coronary artery).MR assessments, including LV functional and extracellular volume matrices (ECV), were extracted from T1 (pre and during-constant infusion of gadolinium) and cine images, respectively, acquired simultaneously during PET acquisition. Cardiac injury and inflammation biomarker measurements of hs-TnT, hs-CRP and erythrocyte sedimentation rate were compared at the 1-month follow-up in this study.Results: At one-month follow-up, a significant increase (10%) of 18FDG/PET myocardial uptake (meanSUVbw) in LAD segments (p=0.04) and ECV in slices at the apex (6%) and base (5%) were detected (p≤0.02). Further, a significant reduction of LV stroke volume (-7%) was seen (p <0.02). No significant changes in all circulating biomarkers at follow-up were shown. Conclusions: 18FDG/PET myocardial uptake and functional MR, including SV and ECV were sensitive to changes at one-month after breast cancer RT with findings suggesting an acute cardiac inflammatory response which is an important cardiotoxicity surrogate to RT. The clinical pilot study (NCT03748030, November 16, 2018) was approved by the Western University Human Research Ethics Board (HSREB ID 112991), funded by Lawson Strategic Research Fund (R19-292).