Intraindividual Comparison Between [18F] PSMA-1007 PET/CT and Multiparametric MRI for Radiotherapy Planning in Primary Prostate Cancer Patients.

Accurate detection and segmentation of the intraprostatic gross tumor volume (GTV) is pivotal for radiotherapy (RT) in primary prostate cancer (PCa) since it influences focal therapy target volumes and the patients' cT stage. The study aimed to compare the performance of multiparametric resonance imaging (mpMRI) with [18F] PSMA-1007 positron emission tomography (PET) for intraprostatic GTV detection as well as delineation and to evaluate their respective influence on RT concepts.

In total, 93 patients from two German University Hospitals with [18F] PSMA-1007-PET/CT and MRI (Freiburg) or [18F] PSMA-1007-PET/MRI (Dresden) were retrospectively enrolled. Validated contouring techniques were applied for GTV-PET and -MRI segmentation. Absolute tumor volume and cT status were determined for each imaging method. The PCa distribution from histopathological reports based on biopsy cores and surgery specimen was used as reference in terms of laterality (unilateral vs. bilateral).

In the Freiburg cohort (n = 84), mpMRI and PET detected in median 2 (range: 1-5) and 3 (range: 1-8) GTVs, respectively (p < 0.01). The median GTV-MRI was significantly smaller than the GTV-PET, measuring 2.05 vs. 3.65 ml (p = 0.0005). PET had a statistically significant higher concordance in laterality with surgery specimen compared to mpMRI (p = 0.04) and biopsy (p < 0.01), respectively. PSMA PET led to more cT2c and cT3b stages, whereas cT3a stage was more pronounced in mpMRI. Based on the cT stage derived from mpMRI and PET information, 21 and 23 as well as 59 and 60 patients, respectively, were intermediate- and high-risk according to the National Comprehensive Cancer Network (NCCN) v1.2022 criteria. In the Dresden cohort (n = 9), similar results were observed.

Intraprostatic GTV segmentation based on [18F] PSMA-1007 PET results in more and larger GTVs compared to mpMRI. This influences focal RT target volumes and cT stage definition, but not the NCCN risk group.

Frontiers in oncology. 2022 Jul 14*** epublish ***

Ioana M Marinescu, Simon K B Spohn, Selina Kiefer, Peter Bronsert, Lara Ceci, Julius Holzschuh, August Sigle, Cordula A Jilg, Alexander Rühle, Tanja Sprave, Nils H Nicolay, Robert Winzer, Jana Rehm, Jörg Kotzerke, Tobias Hölscher, Anca L Grosu, Juri Ruf, Matthias Benndorf, Constantinos Zamboglou

Department of Radiation Oncology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany., Institute for Surgical Pathology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany., Department of Urology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany., Department of Nuclear Medicine, Faculty of Medicine, University of Dresden, Dresden, Germany., German Cancer Consortium (DKTK), Partner Site Dresden, Dresden, Germany., Department of Nuclear Medicine, Medical Center-University of Freiburg, University of Freiburg, Faculty of Medicine, Freiburg im Breisgau, Germany., Department of Radiology, Medical Center-University of Freiburg, University of Freiburg, Faculty of Medicine, Freiburg im Breisgau, Germany.

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