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Updated: May 15, 2026
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A Cognitive Fusion-guided Prostate Biopsy Using Multiparametric Magnetic Resonance Imaging and Transrectal Ultrasound
Published on: March 21, 2025
Interobserver variability in dominant intraprostatic lesion delineation using 68Ga-PSMA PET/CT for localized prostate
Bennur Zeynan Devran1, Ilknur Alsan Cetin1, Feyza Cagliyan2
1Department of Radiation Oncology, Faculty of Medicine, Marmara University, Istanbul, Türkiye.
Summary
Interobserver agreement for prostate cancer lesion delineation using 68Ga-PSMA PET/CT was nearly perfect. However, factors like prostate size and lesion characteristics increased variability, necessitating standardized contouring guidelines.
Area of Science:
- Radiology and Nuclear Medicine
- Oncology
- Medical Imaging Analysis
Background:
- Prostate cancer treatment planning relies on accurate delineation of the dominant intraprostatic lesion (DIL).
- Gallium-68 labeled prostate-specific membrane antigen ligand (68Ga-PSMA) PET/CT is increasingly used for visualizing these lesions.
Purpose of the Study:
- To evaluate interobserver variability in DIL delineation using 68Ga-PSMA PET/CT.
- To analyze the impact of patient and tumor characteristics on this delineation variability.
Main Methods:
- Retrospective analysis of 20 localized prostate cancer patients undergoing radiotherapy.
- Independent DIL volume delineation by three nuclear medicine specialists and one radiation oncologist.
- Assessment of interobserver agreement using intraclass correlation coefficients (ICC) and analysis of influencing factors.
Main Results:
- Almost perfect interobserver agreement (ICC = 0.83) was observed among the four experts.
- DIL volumes were smaller when delineated with access to multiparametric MRI (mpMRI) or by a radiation oncologist compared to nuclear medicine specialists without mpMRI.
- Agreement decreased in patients with larger prostates (>40 cc), longer lesions (>15 mm), higher SUVmax (>10), or extraprostatic extension.
Conclusions:
- While 68Ga-PSMA PET/CT shows high interobserver agreement for DIL delineation, variability exists.
- Factors such as prostate volume, lesion size, SUVmax, and extraprostatic extension influence delineation consistency.
- Development of consensus-based contouring guidelines is crucial for standardizing prostate cancer treatment planning.
