The detection and delineation of the intraprostatic tumor burden plays a crucial role in the personalized treatment of primary prostate cancer. The current gold standard multiparametric magnetic resonance imaging (mpMRI) is used to guide targeted prostate biopsies for initial diagnostic work up and for definitive focal dose-escalated radiotherapy in intermediate and high-risk prostate cancer patients.
However, mpMRI might underestimate the tumor volume and manual gross tumor volume delineation based on mpMRI underlies significant interobserver variability. Thus, novel imaging modalities are warranted to increase the detection rate and/or decrease the interobserver variability during tumor delineation.
This study will prospectively compare two promising advanced medical imaging methods: MRI-RSI and PSMA PET with the current gold-standard mpMRI for tumor detection and delineation in primary prostate cancer patients.
Newly diagnosed and histologically confirmed primary prostate cancer
NCCNv4.2024 risk groups: unfavorable intermediate risk, high-risk and very high-risk
Males, age ≥ 18 years
ECOG performance status 0-2
Contraindications for MRI imaging
No visible tumor on PSMA PET and mpMRI (defined by PIRADs v2.1 ≤2 lesion)
TUR-P of the prostate <1 year ago
Initial PSA >100 ng/ml
Single group
MRI
Diagnostic testMRI-RSI imaging of the prostate (non-invasive)
18F-PSMA1007 PET-CT
Diagnostic testPET scan according to standard protocol
MR-guided TRUS Prostate biopsy
Diagnostic testBiopsy according to standard protocol
Sensitivity
Sensitivity for PSMA PET, conventional mpMRI, MRI-RSI and combined modalities will be calculated on a prostate segment (n=6) level. The prostate cancer distribution in targeted biopsy cores will serve as the ground truth, calculated with the ratio of true positives to the total number of segments with the disease (true positives + false negatives).
Absolute GTV volumes
Conventional mpMRI, MRI-RSI and PSMA-PET derived absolute GTV volumes in ml
Specificity
Specificity for PSMA PET, conventional mpMRI, MRI-RSI and combined modalities will be calculated on a prostate segment (n=6) level. The prostate cancer distribution in targeted biopsy cores will serve as the ground truth, calculated with the ratio of true negatives to the total number of segments without the disease (true negatives + false positives).
ROC-AUC
ROC-AUC for PSMA PET, conventional mpMRI, MRI-RSI and combined modalities on a segment level in comparison with prostate cancer distribution in targeted biopsy cores on a 6 segment level (ground truth). It will be calculated by integrating the area under the TPR (Sensitivity) vs FPR (1-Specificity) curve
Dice Sorensen Coefficient (DSC)
The DSC is defined as followed: twice the size of the intersection of two sets, divided by the sum of the sizes of the two sets. The DSC will be used to compare different GTVs and likewise analyse the geometric overlap and the interobserver variance.
Dose volume histogram parameters in volume (ml) in relation to Gray
Comparison of planning parameters and DVH metrics after PSMA PET and/or MRI-RSI based radiotherapy for target volumes and organs at risk.
Correlation coefficient (Spearman or Pearson)
Quantitative imaging parameters from PSMA-PET, MRI-RSI and mpMRI images will be extracted and cross correlated with the ArteraAI MMAI test score (if available), Prolaris, the Ki-67 staining, the ISUP grade, serum PSA levels and the cTstage
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