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

Abstract

390 Background: There is no reliable way to differentiate between fibrosis/necrosis, teratoma, and viable germ cell tumor in patients receiving post-chemotherapy retroperitoneal lymph node dissection (RPLND) for non-seminomatous germ cell tumor (NSGCT). Functional imaging, including 18F-FDG positron emission tomography/computed tomography (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 Mar 18 – May 19, 10 eligible patients underwent pre-operative 18F-Fluciclovine PET/CT prior to undergoing bilateral full template RPLND or excision of mass (for one re-do retroperitoneal lymph node dissection) in a prospective phase II study. Correlation between PET/CT findings and pathology were evaluated on per patient level. Results: A total of 10 patients underwent 18F-Fluciclovine PET/CT prior to surgery. 9/10 patients received chemotherapy prior to RPLND. Correlation between 18F-Fluciclovine PET/CT and RPLND pathology was seen in 3/10 patients. 5/10 patients with negative anti-18F-FACBC 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. Conclusions: Current management of NSGCT is heavily reliant on sub-optimal imaging modalities that are unable to accurately distinguish between post-chemotherapy necrosis/fibrosis versus residual disease and/or teratoma. Despite a different mechanism of action from 18F-FDG, 18F-Fluciclovine has low sensitivity and specificity for residual teratoma in the retroperitoneum. Clinical trial information: NCT03426865. [Table: see text]