[68 Ga]Ga-FAPI-46 PET/CT for locoregional lymph node staging in urothelial carcinoma of the bladder prior to cystectomy: initial experiences from a pilot analysis.

[68 Ga]Ga-FAPI-46 PET/CT is a novel hybrid imaging method that previously showed additional diagnostic value in the assessment of distant urothelial carcinoma lesions. We hypothesized that patients with bladder cancer benefit from [68 Ga]Ga-FAPI-46 PET/CT prior to radical cystectomy for locoregional lymph node staging.

Eighteen patients underwent [68 Ga]Ga-FAPI-46 PET/CT for evaluation of lymph node (LN) status in predefined LN regions. Two hundred twenty-nine intraoperatively removed LN served as histopathological reference standard.

Urothelial carcinoma (UC) spread was found in ten LN in seven different regions (14.3%). Hereby, [68 Ga]Ga-FAPI-46 PET/CT was positive in four out of seven regions (57.1%) and showed significantly increased FAPI uptake compared to non-pathological regions. In the remaining three out of seven (42.9%) regions, [68 Ga]Ga-FAPI-46 PET/CT was rated negative since no pathological increased FAPI uptake was detected or the proximity of the urinary tract prevented a differentiation from physiological uptake. CT was inconspicuous in these three regions. In total, two FAP-positive LN regions were found without histopathological counterpart. Overall, sensitivity, specificity, positive predictive value, and negative predictive value were 57.1%, 95.2%, 66.7%, and 93.0% for PET imaging.

In summary, this innovative [68 Ga]Ga-FAPI-46 PET/CT method showed high specificity and negative predictive value in patients with bladder UC with a future potential to optimize therapy planning.

European journal of nuclear medicine and molecular imaging. 2024 Jan 18 [Epub ahead of print]

Lena M Unterrainer, Lennert Eismann, Simon Lindner, Franz-Josef Gildehaus, Johannes Toms, Jozefina Casuscelli, Adrien Holzgreve, Sophie C Kunte, Clemens C Cyran, Paula Menold, Alexander Karl, Marcus Unterrainer, Stephan T Ledderose, Christian G Stief, Peter Bartenstein, Alexander Kretschmer, Gerald B Schulz

Department of Nuclear Medicine, LMU University Hospital, LMU Munich, Munich, Germany. ., Department of Urology, LMU University Hospital, LMU Munich, Munich, Germany., Department of Nuclear Medicine, LMU University Hospital, LMU Munich, Munich, Germany., Department of Radiology, LMU University Hospital, LMU Munich, Munich, Germany., Department of Urology, Krankenhaus Barmherzige Brüder, Munich, Germany., Institute of Pathology, LMU Munich, Munich, Germany.