Equivalent tumor detection for early and late FAPI-46 PET acquisition

Abstract

Introduction Positron emission tomography (PET) using small ligands of the fibroblast activation protein (FAP) was recently introduced. However, optimal uptake time has not been defined yet. Here, we systematically compare early (~ 10 min p.i.) and late (~ 60 min p.i.) FAPI-46 imaging in patients with various types of cancer. Methods This is a retrospective single-institutional study. Imaging was performed at the Essen University Hospital, Germany. A total of 69 patients who underwent dual time-point imaging for either restaging (n = 52, 75%) or staging (n = 17, 25%) of cancer were included. Patients underwent PET with two acquisitions: early (mean 11 min, SD 4) and late (mean 66 min, SD 9). Mean injected activity was 148 MBq (SD 33). Results In total, 400 lesions were detected in 69 patients. Two of 400 (0.5%) lesions were only seen in early time-point imaging but not in late time-point imaging. On a per-patient level, there was no significant difference between SUVmax of hottest tumor lesions (Wilcoxon: P = 0.73). Organ uptake demonstrated significant early to late decrease in SUVmean (average ∆SUVmean: − 0.48, − 0.14, − 0.27 for gluteus, liver, and mediastinum, respectively; Wilcoxon: P < 0.001). On a per-lesion basis, a slight increase of SUVmax was observed (average ∆SUVmax: + 0.4, Wilcoxon: P = 0.03). Conclusion In conclusion, early (~ 10 min p.i.) versus late (~ 60 min p.i.) FAPI-46 imaging resulted in equivalent lesion uptake and tumor detection. For improved feasibility and scan volume, we implement early FAPI-46 PET in future clinical and research protocols.

Fibroblast activation protein-based theranostics in cancer research: A state-of-the-art review

“…had an equivalent lesion detection rate compared with a late time point (60 min p.i.) in a previous study 20 .…”

Fibroblast-Activated Protein Inhibitor PET/CT: Cancer Diagnosis and Management

“…Higher tumor-to-organ/blood ratios achieved with FAPI21 and FAPI46, as reported by Loktev et al (3), were promising; however, due to increased uptake of FAPI21 in the oral mucosa, thyroid, and salivary glands, FAPI46 was presumed more favorable. Accordingly, clinical imaging studies with 68 Ga-FAPI46 in a cohort of 69 patients by Ferdinandus et al (22) and six patients by Koerber et al (20) have demonstrated encouraging results. Another novel FAP inhibitor with a different structure based on the squaric acid motif, DOTA.SA.FAPi has also been introduced (23).…”

“…Accordingly, clinical imaging studies with 68 Ga-FAPI46 in a cohort of 69 patients by Ferdinandus et al. ( 22 ) and six patients by Koerber et al. ( 20 ) have demonstrated encouraging results.…”

State-of-the-art of FAPI-PET imaging: a systematic review and meta-analysis

“…One study was designed as a phase I investigation [24]. In 12/23 studies [ 68 Ga]Ga-FAPI was offered as a compassionate drug according to the German Medicinal Product Act § 13(2b) [25,26,35,36,[27][28][29][30][31][32][33][34]. In the remaining 10/23 papers, the trial phase was not speci ed or designated as "not applicable" [37][38][39][40][41][42][43][44][45][46].…”

“…The ndings of this preliminary study suggested a two-compartmental model assess [ 68 Ga]Ga-FAPI kinetics. Ferdinandus et al[32] compared early (~ 10 min p.i.) and late (~ 60 min p.i.)…”