Comparison of MR/ultrasound fusion-guided biopsy with ultrasound-guided biopsy for the diagnosis of prostate cancer

Abstract

Importance: Targeted magnetic resonance (MR)/ultrasound fusion prostate biopsy has been shown to detect prostate cancer. The implications of targeted biopsy alone vs standard extended-sextant biopsy or the 2 modalities combined are not well understood.

Objective: To assess targeted vs standard biopsy and the 2 approaches combined for the diagnosis of intermediate- to high-risk prostate cancer.

Design, setting, and participants: Prospective cohort study of 1003 men undergoing both targeted and standard biopsy concurrently from 2007 through 2014 at the National Cancer Institute in the United States. Patients were referred for elevated level of prostate-specific antigen (PSA) or abnormal digital rectal examination results, often with prior negative biopsy results. Risk categorization was compared among targeted and standard biopsy and, when available, whole-gland pathology after prostatectomy as the "gold standard."

Interventions: Patients underwent multiparametric prostate magnetic resonance imaging to identify regions of prostate cancer suspicion followed by targeted MR/ultrasound fusion biopsy and concurrent standard biopsy.

Main outcomes and measures: The primary objective was to compare targeted and standard biopsy approaches for detection of high-risk prostate cancer (Gleason score ≥ 4 + 3); secondary end points focused on detection of low-risk prostate cancer (Gleason score 3 + 3 or low-volume 3 + 4) and the biopsy ability to predict whole-gland pathology at prostatectomy.

Results: Targeted MR/ultrasound fusion biopsy diagnosed 461 prostate cancer cases, and standard biopsy diagnosed 469 cases. There was exact agreement between targeted and standard biopsy in 690 men (69%) undergoing biopsy. Targeted biopsy diagnosed 30% more high-risk cancers vs standard biopsy (173 vs 122 cases, P < .001) and 17% fewer low-risk cancers (213 vs 258 cases, P < .001). When standard biopsy cores were combined with the targeted approach, an additional 103 cases (22%) of mostly low-risk prostate cancer were diagnosed (83% low risk, 12% intermediate risk, and 5% high risk). The predictive ability of targeted biopsy for differentiating low-risk from intermediate- and high-risk disease in 170 men with whole-gland pathology after prostatectomy was greater than that of standard biopsy or the 2 approaches combined (area under the curve, 0.73, 0.59, and 0.67, respectively; P < .05 for all comparisons).

Conclusions and relevance: 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. Future studies will be needed to assess the ultimate clinical implications of targeted biopsy.

Trial registration: clinicaltrials.gov Identifier: NCT00102544.

Figure 1. Steps for Magnetic Resonance/Ultrasound Fusion–Guided Biopsy

A, Prebiopsy multiparametric magnetic resonance imaging (MP-MRI) that includes anatomical (T2-weighted) and functional (dynamic contrast-enhanced and apparent diffusion coefficient) imaging is obtained and reviewed by a radiologist. Axial images all demonstrate a lesion suspicious for prostate cancer (yellow arrowheads). This lesion would be marked by a radiologist in preparation for fusion biopsy. B, At the time of MR/ultrasound fusion biopsy, a real-time axial transrectal ultrasound is performed to assist with needle guidance. The MR/ultrasound fusion platform overlays the outline of the lesion suspicious for prostate cancer (green line) and contour of the prostate (red line). The platform also synchronizes the transrectal ultrasound image with a location in the prostate and recreates an axial MRI based on the T2-weighted image to correlate with the location of the ultrasound image. A dotted red line demonstrates the path of the needle, and when a biopsy is performed, the location can be recorded as shown here with the yellow line. C, At the conclusion of the biopsy, a 3-dimensional map from the data above is generated, demonstrating the contour of the prostate (red), the location of the tumor lesion (green), the location of the standard extended-sextant biopsies (purple cores), and the location of the targeted MR/ultrasound fusion biopsies (yellow cores).

Figure 2. Flowchart for Study Inclusion Among Men Undergoing Both Targeted and Standard Biopsy

MP-MRI indicates multiparametric magnetic resonance imaging.

Figure 3. Comparison of Pathology From Standard Extended-Sextant Biopsy and Targeted MR/Ultrasound Fusion Biopsy for Prostate Cancer

Pathologic outcomes per individual of targeted magnetic resonance (MR)/ultrasound fusion biopsies compared with standard extended-sextant biopsies for total cohort of 1003 men. Orange shading indicates patients in whom targeted MR/ultrasound fusion biopsy upgraded prostate cancer risk category in relation to standard extended-sextant biopsy. Dark orange indicates cases in which the upgrade was to an intermediate- or high-risk category, Blue shading indicates patients in whom standard extended-sextant biopsy upgraded prostate cancer risk category in relation to targeted MR/ultrasound fusion biopsy. Dark blue indicates cases in which the upgrade was to an intermediate- or high-risk category.

Figure 4. Comparison of Whole-Mount Prostatectomy Pathology Outcome With Targeted Magnetic Resonance (MR)/Ultrasound Fusion Biopsy and Standard Extended-Sextant Biopsy Pathology for Prostate Cancer

Pathologic outcomes of the standard and targeted prostate biopsy as well as the subsequent pathology from the prostatectomy specimen for all 170 men in the study who underwent the surgery. The table can be read by examining the whole-mount pathology of interest on the top, the targeted biopsy pathology of interest on the side, and then the standard biopsy pathology of interest within each cell. For example, the shaded row is the distribution of patients not diagnosed with cancer on targeted biopsy but were ultimately found to have cancer on standard biopsy and prostatectomy.