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

OBJECTIVES: Fluorine 18 (18F)-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 18F-FAPI-04 PET/CT in assessing myocardial injury was evaluated in patients with cancer. METHODS: Myocardial tracer uptake in 168 patients who underwent 18F-FAPI-04 PET/CT was analyzed retrospectively. Maximum and mean standard uptake values in the myocardium (SUVmax-myocardium and SUVmean-myocardium) and blood pool (SUVmax-BP and SUVmean-BP) were recorded. The ratio of SUVmax-myocardium to SUVmean-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). SUVmax-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 18F-FAPI-04 uptake to predict myocardial injury were 0.79 and 0.87 for SUVmax-myocardium and TBR, respectively (p<0.001). CONCLUSION: 18F-FAPI-04 PET/CT imaging identified features of myocardial injury in patients with cancer, providing complementary value beyond tumor staging.