The prostate-specific membrane antigen (PSMA)-targeted radiotracer 18 F-DCFPyL detects tumor neovasculature in metastatic, advanced, radioiodine-refractory, differentiated thyroid cancer
In this study, we show that18F-DCFPyl might detect neovasculature in advanced, metastatic differentiated thyroid cancer (DTC). We first stained the preserved lymph node samples of three patients with DTC who had undergone total thyroidectomy and neck dissection for cervical lymph node metastatic disease to identify PSMA expression, with the PSMA antibody (DAKO Monoclonal). Then, we performed18F-DCFPyl imaging in two other advanced DTC patients with elevated serum thyroglobulin (Tg), indicative of residual disease. We compared the findings with contemporaneous FDG PET/CT scan, conventional Imaging (CT,MRI) and whole-body scan performed with I123/I131. All the three lymph node samples stained positive for PSMA expression in the neovasculature. In the first imaged patient,18F-DCFPyl detected activity within the retropharyngeal CT contrast-enhancing lymph node. Compared to FDG PET/CT, the18F-DCFPyl scan showed a greater SUV (3.1 vs 1.8). In the second imaged patient,18F-DCFPyl showed intense uptake in the L3 vertebra (not seen on the post treatment131I scan or the18F-FDG PET/CT). MRI of the lumbar spine confirmed the presence of sclerotic-lytic lesion at the location, consistent with metastatic disease. Our exploratory study is proof of principle, that the prostate cancer imaging agent18F-DCFPyl may prove useful for the localization of metastases, in patients with metastatic RAI-refractory DTC by detecting neoangiogenesis within the tumor.