Characterization of tumor thrombus in renal cell carcinoma with prostate specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT).

Abstract

Venous tumor thrombus (TT) occurs as part of the natural history of renal cell carcinoma (RCC) local progression in a small minority of cases. MRI is currently the most accurate imaging modality for determining TT extent. PSMA PET/CT may improve RCC staging and IVC TT characterization. The objective of this study was to investigate the role of PSMA PET/CT in defining superior extent of TT in RCC and TT IVC tributary vessel spread, with comparative accuracy vs. MRI, to assess suitability for resection and inform preoperative surgical planning. Patients who underwent PSMA PET/CT for assessment of renal malignancy with TT from 2015 to 2020 at 3 tertiary hospitals in Brisbane, Australia, were retrospectively identified. TT extent was classified using Mayo Clinic levels and compared according to imaging modality. Fourteen patients were included, all of which were clear cell RCC. Ten patients also underwent MRI, 6 of which were concordant in extent according to MRI and PSMA PET. Discordant extent occurred in 4 patients, of which 2 patients had non-PSMA avid thrombus (Mayo level 0 and level 3 on MRI). Further discordance was seen in a patient with adrenal vein and lumbar vein TT only seen on MRI and PSMA PET/CT, respectively. Finally, discordant extent was seen in another patient with Mayo level 4 TT without lumbar vein involvement on MRI vs. level 3 on PSMA PET/CT with lumbar vein involvement. PSMA PET/CT can provide additional information about TT extent in RCC which may not be seen on MRI. Additional information from PSMA PET/CT in this setting may assist surgical planning, in addition to detection of metastatic disease.