Histopathology-validated gross tumor volume delineations of intraprostatic lesions using PSMA-positron emission tomography/multiparametric magnetic resonance imaging

• Published in: Physics and imaging in radiation oncology 2024-07, Vol.31, p.100633, Article 100633
• Main Authors: Grefve, Josefine, Söderkvist, Karin, Gunnlaugsson, Adalsteinn, Sandgren, Kristina, Jonsson, Joakim, Keeratijarut Lindberg, Angsana, Nilsson, Erik, Axelsson, Jan, Bergh, Anders, Zackrisson, Björn, Moreau, Mathieu, Thellenberg Karlsson, Camilla, Olsson, Lars.E., Widmark, Anders, Riklund, Katrine, Blomqvist, Lennart, Berg Loegager, Vibeke, Strandberg, Sara N., Nyholm, Tufve
• Format: Article
• Language: English
• Subjects: Medicin och hälsovetenskap; Original
• ISSN: 2405-6316; 2405-6316
• DOI: 10.1016/j.phro.2024.100633

•Volumetric assessments have been performed, comparing PSMA-positron emission tomography and magnetic resonance-based gross tumor volumes for intraprostatic lesions and histopathology.•Combining multiparametric resonance imaging and PSMA-positron emission tomography enhances Dice similarity coefficient compared to other gross tumor volumes based on single modalities with added margins.•Combining modalities is preferred for accurate intraprostatic lesion depiction. Dose escalation in external radiotherapy of prostate cancer shows promising results in terms of biochemical disease-free survival. Boost volume delineation guidelines are sparse which may cause high interobserver variability. The aim of this research was to characterize gross tumor volume (GTV) delineations based on multiparametric magnetic resonance imaging (mpMRI) and prostate specific membrane antigen-positron emission tomography (PSMA-PET) in relation to histopathology-validated Gleason grade 4 and 5 regions. The study participants were examined with [68Ga]PSMA-PET/mpMRI prior to radical prostatectomy. Four radiation oncologists delineated GTVs in 15 study participants, on four different image types; T2-weighted (T2w), diffusion weighted imaging (DWI), dynamic contrast enhanced (DCE) and PSMA-PET scans separately. The simultaneous truth and performance level estimation (STAPLE) algorithm was used to generate combined GTVs. GTVs were subsequently compared to histopathology. We analysed how Dice similarity coefficient (DSC) and lesion coverage are affected by using single versus multiple image types as well as by adding a clinical target volume (CTV) margin. Median DSC (STAPLE) for different GTVs varied between 0.33 and 0.52. GTVPSMA-PET/mpMRI generated the highest median lesion coverage at 0.66. Combining different image types achieved similar lesion coverage as adding a CTV margin to contours from a single image type, while reducing non-malignant tissue inclusion within the target volume. The combined use of mpMRI or PSMA-PET/mpMRI shows promise, achieving higher DSC and lesion coverage while minimizing non-malignant tissue inclusion, in comparison to the use of a single image type with an added CTV margin.