The Additional Value of PET for MRI Guided Transrectal Prostate Biopsies - Morand Piert

(Length of lecture - 12 minutes)
In this presentation Dr. Piert discusses the random aspects of standard extended-sextant ultrasound-guided biopsy and the study that was designed to assess targeted vs standard biopsy and the 2 approaches combined for the diagnosis of intermediate- to high-risk prostate cancer.   These trial results are published in JAMA, "Comparison of MR/ultrasound fusion-guided biopsy with ultrasound-guided biopsy for the diagnosis of prostate cancer" [1] and they demonstrate that among men undergoing biopsy for suspected prostate cancer, targeted MR/ultrasound fusion biopsy, compared with standard extended-sextant ultrasound-guided biopsy, was associated with increased detection of high-risk prostate cancer and decreased detection of low-risk prostate cancer.  Several studies have reported superior identification of significant prostate cancer using image-guided (targeted) prostate biopsies compared with nontargeted standard biopsies.  He continues that there was a need to better risk-stratify intermediate- and low-risk targets identified on mpMRI. They viewed one potential area of opportunity is in using PET/MRI, in which the multiparametric advantages of MRI can be combined with the functional advantages of PET. The introduction of hybrid PET/MRI scanners promises optimal spatial and temporal registration of PET and MRI data with the added benefit of functional imaging. He describes the interim analysis for the study that was published in the Journal Nuclear Medicine, 18F-Choline PET/MRI: The Additional Value of PET for MRI-Guided Transrectal Prostate Biopsies. [2]  Dr. Piert descibes cases from this prospective trial where they assessed the value of fusion 18F-fluoromethylcholine ((18)F-choline) PET/MRI for image-guided (targeted) prostate biopsies to detect significant prostate cancer (Gleason ≥ 3 + 4) compared with standard (systematic 12-core) biopsies.  18F-choline PET/CT and multiparametric 3T MRI (mpMRI) of the pelvis were performed in 36 subjects with a rising prostate-specific antigen for known (n = 15) or suspected (n = 21) prostate cancer before a prostate biopsy procedure. PET and T2-weighted MR volumes of the prostate were spatially registered using commercially available software. Biopsy targets were selected on the basis of visual appearance on MRI and graded as low, intermediate, or high risk for significant disease. Volumes of interest were defined for MR-identified lesions. 18F-choline uptake measures were obtained from the MR target and a mirrored background volume of interest. The biopsy procedure was performed after registration of real-time transrectal ultrasound with T2-weighted MR and included image-guided cores plus standard cores. Histologic results were determined from standard and targeted biopsy cores as well as prostatectomy specimens (n = 10). The results show that fifteen subjects were ultimately identified with Gleason ≥ 3 + 4 prostate cancer, of which targeted biopsy identified significantly more (n = 12) than standard biopsies (n = 5; P = 0.002). He shows the imaging studies in patients comparing the visible differences.  A total of 52 lesions were identified by mpMRI (19 low, 18 intermediate, 15 high risk), and mpMRI-assigned risk was a strong predictor of final pathology (area under the curve = 0.81; P < 0.001). When the mean 18F-choline target-to-background ratio was used, the addition of 18F-choline to mpMRI significantly improved the prediction of Gleason ≥ 3 + 4 cancers over mpMRI alone (area under the curve = 0.92; P < 0.001). In this study as Dr. Piert presents it where he is an investigator, they conclude that fusion PET/MRI transrectal ultrasound image registration for targeted prostate biopsies is clinically feasible and accurate. The addition of 18F-choline PET to mpMRI improves the identification of significant prostate cancer.   Chlorine PET/CT without MRI is inadequate for characterization of significant prostate cancer. Further, improvements to the imaging increase confidence regarding further patient treatment, reduces frequency of future biopsies and may even be cost effective.  

References: 

1. Siddiqui MM, Rais-Bahrami S, Turkbey B, George AK, Rothwax J, Shakir N, Okoro C, Raskolnikov D, Parnes HL, Linehan WM, Merino MJ, Simon RM, Choyke PL, Wood BJ, Pinto PA. Comparison of MR/Ultrasound Fusion–Guided Biopsy With Ultrasound-Guided Biopsy for the Diagnosis of Prostate Cancer. JAMA. 2015;313(4):390–397. doi:10.1001/jama.2014.17942

Biography:
Dr. Morand Piert is a radiologist at the University of Michigan Hospitals and Health Centers in Ann Arbor, Michigan, with a clinical focus on molecular imaging in oncology. Dr. Piert graduated from the University of Cologne Medical School in 1984 and is board certified in nuclear medicine. 

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