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

IntroductionWe 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 post-chemotherapy 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.MethodsFrom March 2018 to May 2019, 10 eligible patients underwent preoperative ¹⁸F-fluciclovine 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.ResultsA 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.ConclusionsDespite a different mechanism of action from ¹⁸F-FDG, ¹⁸F-fluciclovine has low sensitivity and specificity for residual teratoma in the retroperitoneum.