Abstract 15809: 68 Gallium Fibroblast Activating Protein Inhibitor Positron Emission Tomography is Able to Diagnose Checkpoint Inhibitor-induced Myocarditis

Abstract

Introduction: Checkpoint inhibitors (ICIs) have gained importance in recent years regarding the treatment of a variety of oncologic diseases. The possibilities of diagnosing cardiac adverse autoimmune effects of ICIs are still limited. We aimed to implement FAPI PET/CT imaging in detecting ICI-induced myocarditis. Methods: In a retrospective study, FAPI PET/CT scans of 26 patients who received ICIs from 01/2017 to 10/2019 were analyzed. We compared tracer enrichment in the heart of patients without any signs of a cardiac disease (n=23) to three patients with suspected ICI-induced myocarditis. To exclude any significant coronary heart disease, cardiac catherization was performed. Myocardial biopsies were examined, especially in regard to the infiltration of immune cells. Results: Three patients showed clinical manifestations of an ICI syndrome including myocarditis with elevated levels of hsTnT (175 pg/ml, 1771 pg/ml, 157 pg/ml). Further cardiological assessments revealed ECG abnormalities, lymphocyte infiltration of the myocardium in the biopsies or wall motion abnormalities in echocardiography. These patients’ FAPI PET/CTs showed a locally defined cardiac enrichment of the marker which was absent in patients receiving ICIs without any signs of immunological adverse effects and cardiac impairment (n=23) (Median SUV myocarditis patients: 1.79 (IQR: 1.65, 1.85), median SUV non-myocarditis patients: 1.15 (IQR: 0.955, 1.52)). Conclusions: Myocardial biopsy, the current gold standard of the diagnosis of ICI-induced myocarditis, is susceptible to sampling errors and results arrive within a few days. We provide first evidence that FAPI PET/CT is able to diagnose ICI-induced myocarditis and can demonstrate locally enhanced manifestation of ICI-induced myocarditis on time.