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 2 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 tumours: 466; haematologic 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 < .001). At the per-patient level, there was no significant difference in the SUVmax of tumour 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 < .001), lymphoma (4.75 vs. 4.88; P = 0.043), and most metastatic tumour lesions.

[CONCLUSIONS] Al18F-FAPI-04 PET/CT imaging demonstrated remarkably stable tumour and background uptake with consistently high TBR. Both the tumour 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.