MR-guided biopsy and focal therapy: new options for prostate cancer management

The learning curve for robotic-assisted transperineal MRI/US fusion-guided prostate biopsy

Transperineal fusion prostate biopsy has a considerable learning curve (LC). Robotic-assisted transperineal MRI/Ultrasound fusion-guided biopsy (RA-TP-FBx) may have an easier LC due to automatization. We aimed to assess the LC of RA-TP-FBx and analyze its most difficult steps. We prospectively analyzed cases randomized to a biopsy-naïve urology resident, the chief resident, and an expert urologist in RA-TP-FBx (controls). We also analyzed consecutive cases in the LC of the expert. The LC was defined by procedure time, PCa detection rate (including stratification by PI-RADS), entrustable professional activities (EPA) assessment scores, and the NASA task load index. We collectively performed 246 RA-TP-FBx with the Mona Lisa device. Procedure time for residents decreased steeply from maximum 53 min to minimum 10 min, while the mean procedure time for the expert was 9 min (range 17-5 min). PCa detection for PI-RADS-4 lesions was 57% for the naïve resident, 61% for the chief resident and 62% for the expert. There was also no difference in Pca detection for PI-RADS-4 lesions when comparing the first and second half of the experts' biopsies (p = 0.8). Maximum EPA score was registered after 22 cases. Workload steeply declined. Proficient RA-TP-FBx performance appears feasible after 22 cases regardless of previous experience.

Canadian Association of Radiologists Prostate MRI White Paper

Prostate cancer is the most common malignancy and the third most common cause of death in Canadian men. In light of evolving diagnostic pathways for prostate cancer and the increased use of MRI, which now includes its use in men prior to biopsy, the Canadian Association of Radiologists established a Prostate MRI Working Group to produce a white paper to provide recommendations on establishing and maintaining a Prostate MRI Programme in the context of the Canadian healthcare system. The recommendations, which are based on available scientific evidence and/or expert consensus, are intended to maintain quality in image acquisition, interpretation, reporting and targeted biopsy to ensure optimal patient care. The paper covers technique, reporting, quality assurance and targeted biopsy considerations and includes appendices detailing suggested reporting templates, quality assessment tools and sample image acquisition protocols relevant to the Canadian healthcare context.

Voxel-level Classification of Prostate Cancer on Magnetic Resonance Imaging: Improving Accuracy Using Four-Compartment Restriction Spectrum Imaging

BACKGROUND

Diffusion magnetic resonance imaging (MRI) is integral to detection of prostate cancer (PCa), but conventional apparent diffusion coefficient (ADC) cannot capture the complexity of prostate tissues and tends to yield noisy images that do not distinctly highlight cancer. A four-compartment restriction spectrum imaging (RSI₄ ) model was recently found to optimally characterize pelvic diffusion signals, and the model coefficient for the slowest diffusion compartment, RSI₄ -C₁ , yielded greatest tumor conspicuity.

PURPOSE

To evaluate the slowest diffusion compartment of a four-compartment spectrum imaging model (RSI₄ -C₁ ) as a quantitative voxel-level classifier of PCa.

STUDY TYPE

Retrospective.

SUBJECTS

Forty-six men who underwent an extended MRI acquisition protocol for suspected PCa. Twenty-three men had benign prostates, and the other 23 men had PCa.

FIELD STRENGTH/SEQUENCE

A 3 T, multishell diffusion-weighted and axial T2-weighted sequences.

ASSESSMENT

High-confidence cancer voxels were delineated by expert consensus, using imaging data and biopsy results. The entire prostate was considered benign in patients with no detectable cancer. Diffusion images were used to calculate RSI₄ -C₁ and conventional ADC. Classifier images were also generated.

STATISTICAL TESTS

Voxel-level discrimination of PCa from benign prostate tissue was assessed via receiver operating characteristic (ROC) curves generated by bootstrapping with patient-level case resampling. RSI₄ -C₁ was compared to conventional ADC for two metrics: area under the ROC curve (AUC) and false-positive rate for a sensitivity of 90% (FPR₉₀ ). Statistical significance was assessed using bootstrap difference with two-sided α = 0.05.

RESULTS

RSI₄ -C₁ outperformed conventional ADC, with greater AUC (mean 0.977 [95% CI: 0.951-0.991] vs. 0.922 [0.878-0.948]) and lower FPR₉₀ (0.032 [0.009-0.082] vs. 0.201 [0.132-0.290]). These improvements were statistically significant (P < 0.05).

DATA CONCLUSION

RSI₄ -C₁ yielded a quantitative, voxel-level classifier of PCa that was superior to conventional ADC. RSI classifier images with a low false-positive rate might improve PCa detection and facilitate clinical applications like targeted biopsy and treatment planning.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 2.

Histotripsy: The Next Generation of High-Intensity Focused Ultrasound for Focal Prostate Cancer Therapy

This article reviews the most current methods and technological aspects of high-intensity focused ultrasound (HIFU), which is termed histotripsy. The rationale for focal therapy for prostate carcinoma rather than prostatectomy, which is being used extensively throughout Europe and Asia, is presented, and an argument for why HIFU is the modality of choice for primary therapy and recurrent disease is offered. The article presents a review of the technical advances including higher ultrasound beam energy than current thermal HIFU which allows for more accurate tissue targeting, less collateral tissue damage, and faster treatment times. Finally, the article presents a discussion about the advantage of ultrasound guidance for histotripsy in preference to magnetic resonance imaging guidance primarily based on cost, ease of application, and portability.

Targeted and systematic cognitive freehand-guided transperineal biopsy: is there still a role for systematic biopsy?

OBJECTIVES

To assess whether targeted cognitive freehand-assisted transperineal biopsies using a Precisionpoint^TM device still require additional systematic biopsies to avoid missing clinically significant prostate cancer, and to investigate the benefit of a quadrant-only biopsy approach to analyse whether a quadrant or extended target of the quadrant containing the target only would have been equivalent to systematic biopsy.

PATIENTS AND METHODS

Patients underwent combined systematic mapping and targeted transperineal prostate biopsies at a single institution. Biopsies were performed using the Precisionpoint device (Perineologic, Cumberland, MD, USA) under either local anaesthetic (58%, 163/282), i.v. sedation (12%, 34/282) or general anaesthetic (30%, 85/282). A mean (range) of 24 (5-42) systematic and 4.2 (1-11) target cores were obtained. Magnetic resonance imaging (MRI) scans were reported using the Likert scale. Clinically significant cancer was defined as Gleason 7 or above. Histopathological results were correlated with the presence of an MRI abnormality within a spatial quadrant and the other adjoining or non-adjoining (opposite) quadrants. Histological concordance with radical prostatectomy specimens was analysed.

RESULTS

A total of 282 patients were included in this study. Their mean (range) age was 66.8 (36-80) years, median (range) prostate-specific antigen level 7.4 (0.91-116) ng/mL and mean prostate volume 45.8 (13-150) mL. In this cohort, 82% of cases (230/282) were primary biopsies and 18% (52/282) were patients on surveillance. In all, 69% of biopsies (195/282) were identified to have clinically significant disease (Gleason ≥3 + 4). Any cancer (Gleason ≥3 + 3) was found in 84% (237/282) of patients. Of patients with clinically significant disease, the target biopsies alone picked up 88% (171/195), with systematic biopsy picking up the additional 12% (24/195) that the target biopsies missed. This altered with Likert score; 73% of Likert score 3 disease was detected by target biopsy, 92% of Likert score 4 and 100% of Likert score 5. Target biopsies with additional same-quadrant-only systematic cores picked up 75% (18/24) of significant cancer that was missed on target only, found in the same quadrant as the target.

CONCLUSION

Systematic biopsy is still an important tool when evaluating all patients referred for prostate biopsy, but the need is decreased with increasing suspicion on MRI. Patients with very high suspicion of prostate cancer (Likert score 5) may not require systematic cores, unless representative surrounding biopsies are required for other specific treatments (e.g. focal therapy, or operative planning). More prospective studies are needed to evaluate this in full.

Association Between Tumor Multifocality on Multi-parametric MRI and Detection of Clinically-Significant Prostate Cancer in Lesions with Prostate Imaging Reporting and Data System (PI-RADS) Score 4

OBJECTIVE

To investigate whether presence of multifocality on multi-parametric magnetic resonance imaging would increase the likelihood of detecting clinically-significant prostate cancer in a PI-RADS 4 lesion.

METHODS

We identified patients with at least 1 PI-RADS 4 lesion who underwent multi-parametric magnetic resonance imaging-ultrasound fusion prostate biopsy. Patients were grouped into 1 of 4 cohorts-cohort 1 (a PI-RADS 4 index lesion and an additional PI-RADS 2 or 3 lesion), cohort 2 (single lesion with PI-RADS 4), cohort 3 (2 or more PI-RADS 4 lesions), or cohort 4 (a PI-RADS 4 lesion and an index lesion with PI-RADS 5). We compared the rate of grade group (GG) ≥ 2 pathology on targeted biopsy of PI-RADS 4 lesions between cohorts and evaluated clinical and radiological factors associated with cancer detection.

RESULTS

The overall rate of GG ≥ 2 pathology in the PI-RADS 4 lesions was 35.2%. The rate of GG ≥ 2 pathology in the cohorts 1, 2, 3, and 4 was 21.7%, 36.3%, 49.1%, and 42.7%, respectively (P< .001). On multivariable analysis, age (OR1.06, P < .001), clinical stage T2 (OR1.59, P= .03), prostate-specific antigen density (OR1.43, P < .001), peripheral zone lesion (OR1.62, P = .04), and study cohort (cohort 2 vs 1, OR1.93, P = .006; and cohort 3 vs 1, OR3.28, P < .001) were significantly associated with the risk of GG ≥ 2 in the PI-RADS 4 lesion.

CONCLUSION

On targeted biopsy of the PI-RADS 4 lesions, the proportion of GG ≥ 2 pathology is approximately 35%. Rate of GG ≥ 2 detection in PI-RADS 4 lesions might differ based on their location, multifocality, and PI-RADS classifications of other lesions identified.

Optimizing prostate biopsy techniques

PURPOSE OF REVIEW

Prostate cancer (PCa) diagnostics have undergone a number of changes as a result of efforts to reduce the detection rate of indolent prostate cancer and to increase the hit rate for clinically significant prostate cancer (csPCa). Here, we look at those studies that have shifted our knowledge and the impact these have had on clinical practice.

RECENT FINDINGS

The introduction of multiparametric MRI (mpMRI) and approaches to active surveillance have changed the landscape in prostate cancer diagnostics, reducing the number of men that need biopsy, but increasing the need for accuracy in mapping the extent of prostate cancer. As mpMRI reporting has become more accurate at predicting PCa, biopsy techniques have also evolved towards lesion (PI-RADS score 3-5) targeted biopsies. Uncertainty remains regarding the preferred approach to targeted biopsy, the need for systematic biopsies, and the place of software ultrasound/MRI fusion or in-bore MRI biopsy techniques versus 'cognitive' fusion techniques.

SUMMARY

Prostate biopsies remain essential for the diagnosis of PCa. But how best to do this? Latest guidelines advocate performing both targeted and systematic biopsies. Traditionally, prostate biopsies have been performed transrectally (TRUS) with hospital readmission rates of around 3% mainly because of infection. Additionally, TRUS prostate biopsies can miss anterior prostatic lesions. The transperineal approach addresses both these issues, but has historically required general anaesthetic such that adoption for front-line diagnostics is very difficult. Recent techniques to undertake transperineal biopsy under local anaesthetic have fundamentally changed this paradigm offering the genuine possibility that in 5 years' time, all front-line diagnostic biopsies will be performed as LATP.