Pelvic lymph-node staging with 18F-DCFPyL PET/CT prior to extended pelvic lymph-node dissection in primary prostate cancer - the SALT trial -

J. A. Nieuwenhuijzen,Y. J. L. Bodar,J. P. van der Voorn,B. H. E. Jansen,D. Meijer,M. Wondergem,R. Boellaard,G. J. C. Zwezerijnen,O. S. Hoekstra,R. J. A. van Moorselaar,D. E. Oprea-Lager,A. N. Vis,T. A. Roeleveld

doi:10.1007/s00259-020-04974-w

Abstract

PurposeThe detection of lymph-node metastases (N1) with conventional imaging such as magnetic resonance imaging (MRI) and computed tomography (CT) is inadequate for primarily diagnosed prostate cancer (PCa). Prostate-specific membrane antigen (PSMA) PET/CT is successfully introduced for the staging of (biochemically) recurrent PCa. Besides the frequently used 68gallium-labelled PSMA tracers, 18fluorine-labelled PSMA tracers are available. This study examined the diagnostic accuracy of 18F-DCFPyL (PSMA) PET/CT for lymph-node staging in primary PCa.MethodsThis was a prospective, multicentre cohort study. Patients with primary PCa underwent 18F-DCFPyL PET/CT prior to robot-assisted radical prostatectomy (RARP) with extended pelvic lymph-node dissection (ePLND). Patients were included between October 2017 and January 2020. A Memorial Sloan Kettering Cancer Centre (MSKCC) nomogram risk probability of ≥ 8% of lymph-node metastases was set to perform ePLND. All images were reviewed by two experienced nuclear physicians, and were compared with post-operative histopathologic results.ResultsA total of 117 patients was analysed. Lymph-node metastases (N1) were histologically diagnosed in 17/117 patients (14.5%). The sensitivity, specificity, positive predictive value and negative predictive value for the 18F-DCFPyL PET/CT detection of pelvic lymph-node metastases on a patient level were 41.2% (confidence interval (CI): 19.4–66.5%), 94.0% (CI 86.9–97.5%), 53.8% (CI 26.1–79.6%) and 90.4% (CI 82.6–95.0%), respectively.Conclusion18F-DCFPyL PET/CT showed a high specificity (94.4%), yet a limited sensitivity (41.2%) for the detection of pelvic lymph-node metastases in primary PCa. This implies that current PSMA PET/CT imaging cannot replace diagnostic ePLND. Further research is necessary to define the exact place of PSMA PET/CT imaging in the primary staging of PCa.

Highlights

Prostate cancer (PCa) is the most frequently diagnosed cancer in men in the Western world [1, 2]
Study design and patient population. This was a prospective, non-randomized study evaluating the accuracy of 18F-DCFPyL PET/computed tomography (CT) for detecting pelvic lymphnode metastases in patients with primary PCa undergoing radical surgery
18F-DCFPyL PET/CT imaging demonstrated a limited sensitivity for pelvic lymph-node metastases of 41.2%, at 94.0% specificity

Summary

Introduction

Prostate cancer (PCa) is the most frequently diagnosed cancer in men in the Western world [1, 2]. Accurate assessment of local tumour stage (T-stage), regional lymph-node involvement (N-stage) and screening for distant metastases (M-stage) is essential, since it significantly affects patient follow-up, therapeutic decisions and oncological outcome [3]. Conventional imaging studies such as computed tomography (CT) and magnetic resonance imaging (MRI) have moderate sensitivity for the detection of lymph-node metastases (42% and 39%, respectively) [4,5,6]. Extended pelvic lymph-node dissection (ePLND) remains the preferred technique for nodal staging. It is an invasive procedure, associated with complications such as lymphocele, deep venous thrombosis, and longer hospital stay [7]

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Results

Conclusion