18F-DCFPyL PET/CT in primary staging of prostate cancer

Abstract

BackgroundCorrect primary staging is mandatory for therapy selection and to determine prognosis in prostate cancer patients. Commonly used diagnostic procedures including Computed Tomography (CT), Magnetic Resonance Imaging, Choline Positron Emission Tomography/Computed Tomography (PET/CT) and extended lymph node dissection (ePLND) have suboptimal diagnostic accuracy for primary staging. PSMA targeting radiopharmaceuticals have shown better diagnostic accuracy than commonly used imaging procedures. This study presents data of a retrospective cohort of patients that received PET/CT with 18F-DCFPyL for staging of primary prostate cancer.MethodsFrom November 2016 until April 1018 all consecutive patients that received 18F-DCFPyL PET/CT for primary staging of prostate cancer were included in the study. 18F-DCFPyL PET findings in the primary tumour were scored. Detection rates of metastases were calculated for different clinical parameters, including PSA, Gleason score, clinical T-stage and risk on having lymph node metastases according to established prediction models. Subsequently, for lymph nodes, 18F-DCFPyL PET findings were compared to morphological features on the co-registered contrast enhanced CT and, for patients with risk on lymph node metastases > 5% according to prediction models, it was scored whether 18F-DCFPyL positive lymph nodes were present at locations that would be resected during ePLND, as well as presence of positive nodes or other metastases outside this area.ResultsOne hundred thirty-three patients were analysed. Increased 18F-DCFPyL uptake the in primary tumour was found in 98% of the patients. In 69 patients increased 18F-DCFPyL uptake was found in lymph nodes, of which 48 and 45% had unsuspicious morphological characteristics on CT (size cut-off ≤6 mm short axis), for locoregional and distant nodes, respectively. In 43% of patients 18F-DCFPyL PET/CT detected lesions suspicious for metastases outside the ePLND area. 18F-DCFPyL PET/CT detection rates are in line with established prediction models of risk on lymph node metastases.Conclusion18F-DCFPyL PET/CT shows more lymph nodes with pathological characteristics as compared to the co-registered contrast enhanced CT alone. 18F-DCFPyL PET/CT detects lesions suspicious for metastases outside the ePLND area in 43% of patients, with risk on lymph node metastases exceeding 5%, which therefore may be excluded for ePLND. 18F-DCFPyL PET/CT detection rates are in line with established prediction models of risk on lymph node metastases. Large prospective trials that compare 18F-DCFPyL findings with histopathological findings after ePLND are needed in order elucidate sensitivity of 18F-DCFPyL PET/CT and to position 18F-DCFPyL PET/CT in the staging algorithm for primary prostate cancer.