Prostate cancer detection with magnetic resonance-ultrasound fusion biopsy: The role of systematic and targeted biopsies

Abstract

Background: The current study was conducted to evaluate the performance of magnetic resonance (MR)-ultrasound-guided fusion biopsy in diagnosing clinically significant prostate cancer (csCaP).

Methods: A total of 1042 men underwent multiparametric MR imaging (mpMRI) and fusion biopsy consecutively in a prospective trial (2009-2014). An expert reader graded mpMRI regions of interest (ROIs) as 1 to 5 using published protocols. The fusion biopsy device was used to obtain targeted cores from ROIs (when present) followed by a fusion image-guided, 12-core systematic biopsy in all men, even if no suspicious ROI was noted. The primary endpoint of the study was the detection of csCaP (ie, Gleason score ≥ 7).

Results: Among 825 men with ≥ 1 suspicious ROI of ≥ grade 3, 289 (35%) were found to have csCaP. Powerful predictors of csCaP were ROI grade (grade 5 vs grade 3: odds ratio, 6.5 [P<.01]) and prostate-specific antigen density (each increase of 0.05 ng/mL/cc: odds ratio, 1.4 [P<.01]). Combining systematic and targeted biopsies resulted in the detection of more patients with csCaP (289 patients) than targeting (229 patients) or systematic (199 patients) biopsy alone. Among patients with no suspicious ROI, 35 (16%) were found to have csCaP on systematic biopsy.

Conclusions: In this prospective trial, MR-ultrasound fusion biopsy allowed for the detection of csCaP, with a direct relationship noted with ROI grade and prostate-specific antigen density. The combination of targeted and systematic biopsy detected more csCaP than either modality alone; systematic biopsies revealed csCaP in 16% of men with no suspicious MRI target. The advantages of this new biopsy method are apparent, but issues of cost, training, and reliability await resolution before its widespread adoption.

Keywords: biopsy; cancer staging; diagnostic imaging; magnetic resonance imaging; prostate cancer.

Figure 1

Pathway for performance of MR-US fusion biopsy in a sample patient. From the mpMRI, a region of interest (ROI (arrows) is identified on 3 sequences: T2 (A), DWI (B), and DCE (C). MR images are co-registered with real-time transrectal ultrasound in the image-fusion device (Artemis, Eigen) (D). Biopsies (tan lines) are performed on a 3-dimensional reconstruction of the prostate made by the fusion device; the model incorporates the ROI (in blue) as an anterior target; targeted and systematic cores are obtained (E). The radical prostatectomy specimen processed with whole-mount sectioning shows the index tumor corresponding to the ROI (large arrow) (F). Small arrow points to a secondary lesion. Men with no suspicious ROIs on mpMRI had systematic biopsies taken via a 12-point scalable grid, performed with the fusion biopsy device (systematic grid, coronal view).

Figure 2

Diagnostic performance of systematic biopsy, targeted biopsy, and combined approach among patients, whose mpMRI revealed at least one ROI of grade ≥3 (n=825). Number of patients diagnosed with CaP (vertical axis) vs biopsy strategy is shown. Combining targeted and systematic biopsies resulted in detection of 60 clinically-significant cancers undetected by either alone (light gray, p<0.001 vs systematic and targeted alone), and an additional 15 high-risk cases (black, p<0.001 vs systematic and targeted approach).

Figure 3

Relationship between ROI grade and presence of cancer. This figure shows the proportion of patients with ≥ 1 ROI on MRI (n=825) with a diagnosis of csCaP (n=289, 35%) (y-axis) stratified by ROI grade (x-axis). Combination biopsy (black checked bars) outperformed systematic biopsy (dark diagonal bars) and targeted biopsy (light hatched bars) across all ROI grades (p<0.001). Overall, 80% of patients with a grade 5 ROI had csCaP (vs 24% grade 3 ROI, OR 9.05, 95% CI 4.96 – 16.50).