Theranostics 2017; 7(1):228-237. doi:10.7150/thno.16638

Research Paper

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

Constantinos Zamboglou1✉, Vanessa Drendel2, Cordula A. Jilg3, Hans C. Rischke1, Teresa I. Beck4, Wolfgang Schultze-Seemann3, Tobias Krauss5, Michael Mix4, Florian Schiller4, Ulrich Wetterauer3, Martin Werner2, Mathias Langer5, Michael Bock5, Philipp T. Meyer4, Anca L. Grosu1

1. Department of Radiation Oncology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany; German Cancer Consortium (DKTK), Partner Site Freiburg, Germany;
2. Department of Pathology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany; German Cancer Consortium (DKTK), Partner Site Freiburg, Germany;
3. Department of Urology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany; German Cancer Consortium (DKTK), Partner Site Freiburg, Germany;
4. Department of Nuclear Medicine, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany; German Cancer Consortium (DKTK), Partner Site Freiburg, Germany;
5. Department of Radiology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany; German Cancer Consortium (DKTK), Partner Site Freiburg, Germany.

Abstract

Purpose: The exact detection and delineation of the intraprostatic tumour burden is crucial for treatment planning in primary prostate cancer (PCa). We compared 68Ga-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 68Ga-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), 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, 68Ga-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.

Keywords: Prostate cancer, PSMA PET/CT, multiparametric MRI, histopathology.

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How to cite this article:
Zamboglou C, Drendel V, Jilg CA, Rischke HC, Beck TI, Schultze-Seemann W, Krauss T, Mix M, Schiller F, Wetterauer U, Werner M, Langer M, Bock M, Meyer PT, Grosu AL. 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. Theranostics 2017; 7(1):228-237. doi:10.7150/thno.16638. Available from http://www.thno.org/v07p0228.htm