Current imaging techniques may not detect all prostate cancer (PCa) lesions.
To evaluate positron emission tomography (PET)/computed tomography (CT) using the radiolabeled GRPR antagonist probe BAY86-7548 (68Ga-RM2) for localization of newly diagnosed PCa in comparison with multiparametric magnetic resonance imaging (mpMRI), histopathology, and immunohistochemistry (IHC).
This was a prospective study of 16 men with biopsy-proven PCa (2 low, 8 intermediate, and 6 high risk). 68Ga-RM2 PET/CT was performed within 4 wk after mpMRI and within 2 wk before radical prostatectomy and extended bilateral pelvic lymph node dissection.
The presence of cancer was evaluated by blinded specialists using a 5-point Likert scale, with lesions scoring 4 or 5 considered positive, on 68Ga-RM2 PET/CT, mpMRI, and 68Ga-RM2 PET/CT-mpMRI fused images for each of 12 anatomic areas of the prostate. Whole-mount, step-section pathology served as the reference standard. Expression of GRPR and prostate-specific membrane antigen (PSMA) was analyzed via IHC of tumor paraffin sections.
Of 192 areas analyzed, 128 contained cancer. The sensitivity, specificity, and accuracy of 68Ga-RM2 PET/CT imaging and mpMRI did not differ significantly; fusing the images maximized the sensitivity and accuracy (85.2% and 83.9%, respectively) and averaged the specificity (81.3%). The area under the receiver operating characteristic curve was 0.76 for PET visual analysis, 0.72 for PET quantitative analysis, 0.76 for mpMRI, and 0.85 for combined PET/CT and mpMRI analysis. 68Ga-RM2 uptake did not correlate with Gleason score. IHC analysis revealed weaker staining for GRPR than for PSMA, and the expression of these markers was not correlated (r=0.3882). The major limitation is the small sample size.
68Ga-RM2 PET/CT is promising for detection and localization of primary PCa, and complements mpMRI. GRPR expression appears to be independent from PSMA expression, suggesting that GRPR- and PSMA-targeted PET imaging may be complementary.
This pilot prospective study shows that a positron emission tomography probe that binds to a marker of prostate cancer, GRPR, improves the ability of magnetic resonance imaging to detect prostate cancer.
European urology oncology. 2018 Sep 22 [Epub]
Karim A Touijer, Laure Michaud, Herbert A Vargas Alvarez, Anuradha Gopalan, Susanne Kossatz, Mithat Gonen, Bradley Beattie, Israel Sandler, Serge Lyaschenko, James A Eastham, Peter T Scardino, Hedvig Hricak, Wolfgang A Weber
Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY, USA. Electronic address: ., Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, USA., Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, NY, USA., Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, New York, NY, USA., Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA., Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY, USA.