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

Josefine Grefve; Karin Söderkvist; Adalsteinn Gunnlaugsson; Kristina Sandgren; Joakim Jonsson; Angsana Keeratijarut Lindberg; Erik Nilsson; Jan Axelsson; Anders Bergh; Björn Zackrisson; Mathieu Moreau; Camilla Thellenberg Karlsson; Lars E Olsson; Anders Widmark; Katrine Riklund; Lennart Blomqvist; Vibeke Berg Loegager; Sara N Strandberg; Tufve Nyholm

doi:10.1016/j.phro.2024.100633

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

Phys Imaging Radiat Oncol. 2024 Aug 22:31:100633. doi: 10.1016/j.phro.2024.100633. eCollection 2024 Jul.

Authors

Josefine Grefve¹, Karin Söderkvist², Adalsteinn Gunnlaugsson³, Kristina Sandgren¹, Joakim Jonsson¹, Angsana Keeratijarut Lindberg¹, Erik Nilsson¹, Jan Axelsson¹, Anders Bergh⁴, Björn Zackrisson², Mathieu Moreau³, Camilla Thellenberg Karlsson², Lars E Olsson⁵, Anders Widmark², Katrine Riklund⁶, Lennart Blomqvist⁶, Vibeke Berg Loegager⁷, Sara N Strandberg⁶, Tufve Nyholm¹

Affiliations

¹ Department of Diagnostics and Intervention, Radiation Physics, Umea University, Umea, Sweden.
² Department of Diagnostics and Intervention, Oncology, Umea University, Umea, Sweden.
³ Department of Hematology, Oncology and Radiation Physics, Skane University Hospital, Lund University, Lund, Sweden.
⁴ Department of Medical Biosciences, Pathology, Umea University, Umea, Sweden.
⁵ Department of Translational Medicine, Medical Radiation Physics, Lund University, Malmo, Sweden.
⁶ Department of Diagnostics and Intervention, Diagnostic Radiology, Umea University, Umea, Sweden.
⁷ Department of Radiology, Copenhagen University Hospital in Herlev, Herlev, Denmark.

Abstract

Background and purpose: 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.

Material and methods: 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.

Results: Median DSC (STAPLE) for different GTVs varied between 0.33 and 0.52. GTV_{PSMA-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.

Conclusion: 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.