18 F‑FAPI‑04 PET/CT imaging of fibroblast activating protein reveals myocardial injury beyond cancer staging

Objectives Fluorine 18 ( 18 F)‐labeled fibroblast activation protein inhibitor‐04 (denoted as FAPI‐04) positron emission tomography/computed tomography (PET/CT) has showed excellent diagnostic performance for multiple solid tumors. However, its utility in characterizing myocardial injury has not yet been reported. In this study, the additional value of 18 F‐FAPI‐04 PET/CT in assessing myocardial injury was evaluated in patients with cancer. Methods Myocardial tracer uptake in 168 patients who underwent 18 F‐FAPI‐04 PET/CT was analyzed retrospectively. Maximum and mean standard uptake values in the myocardium (SUV max‐myocardium and SUV mean‐myocardium ) and blood pool (SUV max‐BP and SUV mean‐BP ) were recorded. The ratio of SUV max‐myocardium to SUV mean‐BP was denoted as the target‐to‐background ratio (TBR). Myocardial uptake higher than the background was visual uptake (n = 49), and uptake consistent with the background was no visual uptake (n = 119). Patients with abnormal uptake but without cardiovascular disease (CVD) were followed up. Results Myocardial uptake higher than the background was visual uptake (n = 49), and uptake consistent with the background was no visual uptake (n = 119). The prevalence of hypertension, diabetes mellitus (DM), CVD, and levels of cardiac troponin T and pro‐BNP were higher in the visual uptake group (all p <0.05). SUV max‐myocardium and TBR were significantly correlated with age and pro‐BNP levels ( p <0.05). Hypertension, DM, CVD, pro‐BNP>125pg/mL, and prior chest radiotherapy were independent risk factors for abnormal uptake ( p <0.05). The area under the curve (AUC) values of myocardial 18 F‐FAPI‐04 uptake to predict myocardial injury were 0.79 and 0.87 for SUV max‐myocardium and TBR, respectively ( p <0.001). Conclusion 18 F‐FAPI‐04 PET/CT imaging identified features of myocardial injury in patients with cancer, providing complementary value beyond tumor staging.