Performance characteristics of 18F-fluciclovine positron emission tomography/computed tomography prior to retroperitoneal lymph node dissection

Introduction: We aimed to determine whether anti-1-amino-3-18F-fluorocyclobutane-1- carboxylic acid (18F-fluciclovine) positron emission tomography/computed tomography (PET/CT) can accurately detect residual non-seminomatous germ cell tumor (NSGCT) prior to retroperitoneal lymph node dissection (RPLND). There is no reliable way to differentiate between fibrosis/necrosis, teratoma, and viable germ cell tumor in patients receiving postchemotherapy RPLND. Functional imaging, including 18F-fludeoxyglucose (18F-FDG) PET/CT, has been disappointing. Due to the need for better imaging modalities, our prospective, pilot study aims to investigate the accuracy of 18F-fluciclovine PET/CT in detecting residual tumor prior to RPLND. Methods: From March 2018 to May 2019, 10 eligible patients underwent preoperative 18Ffluciclovine PET/CT prior to undergoing bilateral, full-template RPLND or excision of mass (for one re-do RPLND) in a prospective, phase 2 study. Correlation between 18F-fluciclovine PET/CT and RPLND pathology were evaluated on a per-patient level. Results: A total of 10 patients (mean age 29±7.6 years) underwent 18F-fluciclovine PET/CT prior to surgery. Nine of 10 patients received chemotherapy prior to RPLND. Correlation between 18F-fluciclovine PET/CT and RPLND pathology was seen in 3/10 (30%) patients. Five of 10 patients (50%) with negative 18F-fluciclovine PET/CT were found to have residual disease/teratoma on RPLND. Compared to the reference standard of RPLND, 18F-fluciclovine PET/CT demonstrated 29% sensitivity and 33% specificity. No patients experienced any adverse events due to 18F-fluciclovine PET/CT. Conclusions: Despite a different mechanism of action from 18F-FDG, 18F-fluciclovine has low sensitivity and specificity for residual teratoma in the retroperitoneum.