Comparison of ⁶⁸Ga-HBED-CC PSMA-PET/CT and multiparametric MRI for gross tumour volume detection in patients with primary prostate cancer based on slice by slice comparison with histopathology

Abstract

Purpose: The exact detection and delineation of the intraprostatic tumour burden is crucial for treatment planning in primary prostate cancer (PCa). We compared 68 Ga-HBED-CC-PSMA PET/CT with multiparametric MRI (mpMRI) for diagnosis and tumour delineation in patients with primary PCa based on slice by slice correlation with histopathological reference material. Methodology: Seven patients with histopathologically proven primary PCa underwent 68 Ga-HBED-CC-PSMA PET/CT and MRI followed by radical prostatectomy. Resected prostates were scanned by ex-vivo CT in a special localizer and prepared for histopathology. Invasive PCa was delineated on a HE stained histologic tissue slide and matched to ex-vivo CT to obtain gross tumor volume (GTV-)histo. Ex-vivo CT including GTV-histo and MRI data were matched to in-vivo CT(PET). Consensus contours based on MRI (GTV-MRI), PSMA PET (GTV-PET) or the combination of both (GTV-union/-intersection) were created. In each in-vivo CT slice the prostate was separated into 4 equal segments and sensitivity and specificity for PSMA PET and mpMRI were assessed by comparison with histological reference material. Furthermore, the spatial overlap between GTV-histo and GTV-PET/-MRI and the Sørensen-Dice coefficient (DSC) were calculated. In the case of multifocal PCa (4/7 patients), SUV values (PSMA PET) and ADC-values (diffusion weighted MRI) were obtained for each lesion. Results: PSMA PET and mpMRI detected PCa in all patients. GTV-histo was detected in 225 of 340 segments (66.2%). Sensitivity and specificity for GTV-PET, GTV-MRI, GTV-union and GTV-intersection were 75% and 87%, 70% and 82%, 82% and 67%, 55% and 99%, respectively. GTV-histo had on average the highest overlap with GTV-union (57±22%), which was significantly higher than overlap with GTV-MRI (p=0.016) and GTV-PET (p=0.016), respectively. The mean DSC for GTV-union, GTV-PET and GTV-MRI was 0.51 (±0.18), 0.45 (±0.17) and 0.48 (±0.19), Ivyspring International PublisherTheranostics 2017, Vol. 7, Issue 1 http://www.thno.org 229 respectively. In every patient with multifocal PCa there was one lesion which had both the highest SUV and the lowest ADC-value (mean and max). Conclusion: In a slice by slice analysis with histopathology, 68 Ga-HBED-CC-PSMA PET/CT and mpMRI showed high sensitivity and specificity in detection of primary PCa. A combination of both methods performed even better in terms of sensitivity (GTV-union) and specificity (GTV-intersection). A moderate to good spatial overlap with GTV-histo was observed for PSMA PET/CT and mpMRI alone which was significantly improved by GTV-union. Further studies are warranted to analyse the impact of these preliminary findings for diagnostic (multimodal guided TRUS biopsy) and therapeutic (focal therapy) strategies in primary PCa.

Positron‐emission tomography imaging in urological oncology: Current aspects and developments

“…Here, 68 Ga‐PSMA PET/MRI significantly outperformed multiparametric MRI or 68 Ga‐PSMA PET with a sensitivity and specificity for tumor localization on a sextant base of 76% and 97% (58% and 82% for multiparametric MRI, 64% and 94% for 68 Ga‐PSMA PET, respectively) . Furthermore, several studies assessing intraprostatic tumor localization in correlation to histopathology by 68 Ga‐PSMA PET/CT showed significantly higher 68 Ga‐PSMA uptake in positive segments compared with negative segments (SUV max 11.8 vs 4.9 and 11.0 vs 2.7, respectively, P < 0.001 each) …”

Prostate-Specific Membrane Antigen Ligands for Imaging and Therapy

“…Increasing numbers of studies have investigated the potential of 68 Ga-PSMA-11 for intraprostatic tumor localization (97)(98)(99)(100)(101)(102). For example, on the basis of a 6-segment model per slice, histopathologically positive segments (n 5 100 in 21 patients) had significantly higher 68 Ga-PSMA-11 uptake than negative segments (SUV max , 11.8 vs. 4.9), suggesting an SUV max of 6.5 as an optimal discriminator (sensitivity of 67% and specificity of 92% for the detection of tumor-involved segments) (97).…”

PSMA Ligands for PET Imaging of Prostate Cancer

“…With regard to intraprostatic tumor localization by 68 Ga-PSMA-11 PET/CT, imaging findings were correlated with histopathology using segment-or voxel-based approaches in several studies (50)(51)(52). These studies demonstrated relatively similar results, with a significantly higher 68 Ga-PSMA-11 uptake in positive segments than in negative segments (SUV max of 11.8 vs. 4.9 and 11.0 vs. 2.7, respectively, P , 0.001 each) (50,51).…”