A clinical study of the feasibility of early Al18F-fibroblast activation protein inhibitor-04 PET/CT scans

Objectives In this study, we systematically compared early Al18F-FAPI-04 imaging performed at 15 and 30 minutes post-injection in patients with various types of cancer to determine whether an early imaging scan can fulfil the criteria for clinical diagnosis. Methods The cohort comprised 101 patients with various cancer diagnoses who underwent Al18F-FAPI-04 PET/CT imaging at two time points: 15 and 30 minutes post-injection. Tracer uptake was assessed using SUVmax, SUVmean and TBR. Results In total, 560 lesions were detected among 101 patients (solid tumors: 466; hematologic neoplasms: 94), all of which were identified at both imaging time points. Between 15 and 30 minutes post-injection, the SUVmean of various organs decreased rapidly (the average ΔSUVmean for the brain, liver, and blood pool was −0.04, −0.07, and −0.21, respectively; P < 0.001). At the per-patient level, there was no significant difference in the SUVmax of tumor lesions. On a per-lesion basis, SUVmax remained largely consistent, showing no statistically significant variation. However, a higher TBR at 30 minutes was observed in liver cancer (4.14 vs. 4.54; P < 0.001), lymphoma (4.75 vs. 4.88; P = 0.043), and most metastatic tumor lesions. Conclusions Al18F-FAPI-04 PET/CT imaging demonstrated remarkably stable tumor and background uptake with consistently high TBR. Both the tumor detection rate and lesion uptake were comparable at 15 and 30 minutes post-injection. Therefore, performing a FAPI-04 scan as early as 15 minutes post-injection appears feasible. Advances in knowledge Al18F-FAPI-04 PET/CT enables early imaging, significantly reducing patient waiting times.