68Ga-PSMA PET/CT compared with MRI/CT and diffusion-weighted MRI for primary lymph node staging prior to definitive radiotherapy in prostate cancer: a prospective diagnostic test accuracy study.

The aim was to compare the diagnostic accuracy of 68Ga-PSMA PET/CT with conventional cross-sectional imaging and diffusion-weighted MRI (DW-MRI) for detecting lymph node metastasis (LNM) to stage prostate cancer patients. Twenty consecutive, newly- diagnosed prostate cancer patients were prospectively enrolled and underwent 68Ga-PSMA-11 PET/CT, anatomical MRI or contrast-enhanced CT, and DW-MRI prior to laparoscopic, template-based, extended lymph node dissection. Histopathological findings served as the reference test.

Histopathology showed LNM in 13 of 20 patients (19 high-risk, 1 intermediate risk). Five patients had metastasis-suspected lymph nodes on 68Ga-PSMA PET/CT. Patient-based analysis showed that the sensitivity and specificity for detecting LNM were 39% and 100% with 68Ga-PSMA PET/CT, 8% and 100% with MRI/CT, and 36% and 83% with DW-MRI, respectively. The positive and negative predictive values were 100% and 49% with 68Ga-PSMA PET/C, 100% and 37% with MRI/CT, and 80% and 42% with DW-MRI. Of 573 dissected lymph nodes, 33 were LNM from 26 regions. True-positive LNM on 68Ga-PSMA PET/CT was 9-11 mm in diameter, whereas false-negative LNM had a median diameter of 4 mm, with only 3 of 30 lymph nodes being larger than 10 mm. LNM were positive for PSMA by immunostaining.

The sensitivity of 68Ga-PSMA PET/CT was notably better than that of MRI/CT and comparable to that of DW-MRI. Some false positive findings with DW-MRI reduced its specificity and positive predictive value compared with those of 68Ga-PSMA PET/CT and MRI/CT.

World journal of urology. 2019 Jun 12 [Epub ahead of print]

Lars J Petersen, Julie B Nielsen, Niels C Langkilde, Astrid Petersen, Ali Afshar-Oromieh, Nandita M De Souza, Katja De Paepe, Rune V Fisker, Dennis T Arp, Jesper Carl, Uwe Haberkorn, Helle D Zacho

Department of Nuclear Medicine, Aalborg University Hospital, Hobrovej 18-22, 9000, Aalborg, Denmark. ., Department of Nuclear Medicine, Aalborg University Hospital, Hobrovej 18-22, 9000, Aalborg, Denmark., Department of Clinical Medicine, Aalborg University, Aalborg, Denmark., Department of Pathology, Aalborg University Hospital, Aalborg, Denmark., Department of Nuclear Medicine, Bern University Hospital, Bern, Switzerland., The Institute of Cancer Research and Royal Marsden NHS Foundation Trust, London, UK., Department of Medical Physics, Aalborg University Hospital, Aalborg, Denmark., Department of Nuclear Medicine, University Hospital Heidelberg, Heidelberg, Germany.