Some prostate cancers are invisible to magnetic resonance imaging!

Landmarks in the evolution of prostate biopsy

Approaches and techniques used for diagnostic prostate biopsy have undergone considerable evolution over the past few decades: from the original finger-guided techniques to the latest MRI-directed strategies, from aspiration cytology to tissue core sampling, and from transrectal to transperineal approaches. In particular, increased adoption of transperineal biopsy approaches have led to reduced infectious complications and improved antibiotic stewardship. Furthermore, as image fusion has become integral, these novel techniques could be incorporated into prostate biopsy methods in the future, enabling 3D-ultrasonography fusion reconstruction, molecular targeting based on PET imaging and autonomous robotic-assisted biopsy.

Identifying Risk Factors for MRI-Invisible Prostate Cancer in Patients Undergoing Transperineal Saturation Biopsy

Purpose

Prostatic multi-parametric magnetic resonance imaging (mpMRI) has markedly improved the assessment of men with suspected prostate cancer (PCa). Nevertheless, as mpMRI exhibits a high negative predictive value, a negative MRI may represent a diagnostic dilemma. The aim of this study was to evaluate the incidence of positive transperineal saturation biopsy in men who have negative mpMRI and to analyse the factors associated with positive biopsy in this scenario.

Patients and Methods

A retrospective study of men with normal mpMRI and suspicion of PCa who underwent saturation biopsy (≥20 cores) was carried out. A total of 580 patients underwent transperineal MRI/transrectal ultrasound fusion targeted biopsies or saturation prostate biopsies from January 2017 to September 2020. Of them, 73 had a pre-biopsy negative mpMRI (with Prostate Imaging – Reporting and Data System, PI-RADS, ≤2) and were included in this study. Demographics, clinical characteristics, data regarding biopsy results and potential predictive factors of positive saturation biopsy were collected. Univariate and multivariate logistic regression analyses were used to identify independent risk factors for MRI-invisible PCa.

Results

The detection rate of PCa with saturation biopsy in patients with negative MRI was 34/73 (46.58%). Out of 34 MRI-invisible prostate cancers detected, 12 (35.29%) were clinically significant PCa (csPCa) forms. Regarding factors of positive biopsy, in univariate analysis, the use of 5-alpha reductase inhibitors and free:total prostate-specific antigen (PSA) ratio were associated with the result of the saturation biopsy. In multivariate analysis, only an unfavourable free:total PSA ratio remained a risk factor (OR 11.03, CI95% 1.93–63.15, p=0.01). Furthermore, multivariate logistic analysis demonstrated that prostate volume >50mL significantly predicts the absence of csPCa on saturation biopsy (OR 0.11, 95% CI 0.01–0.94, p=0.04).

Conclusion

A free:total PSA ratio <20% is a risk factor for MRI-invisible PCa. Saturation biopsy could be considered in patients with suspected PCa, despite having a negative MRI.

T1 and T2 MR fingerprinting measurements of prostate cancer and prostatitis correlate with deep learning-derived estimates of epithelium, lumen, and stromal composition on corresponding whole mount histopathology

OBJECTIVES

To explore the associations between T1 and T2 magnetic resonance fingerprinting (MRF) measurements and corresponding tissue compartment ratios (TCRs) on whole mount histopathology of prostate cancer (PCa) and prostatitis.

MATERIALS AND METHODS

A retrospective, IRB-approved, HIPAA-compliant cohort consisting of 14 PCa patients who underwent 3 T multiparametric MRI along with T1 and T2 MRF maps prior to radical prostatectomy was used. Correspondences between whole mount specimens and MRI and MRF were manually established. Prostatitis, PCa, and normal peripheral zone (PZ) regions of interest (ROIs) on pathology were segmented for TCRs of epithelium, lumen, and stroma using two U-net deep learning models. Corresponding ROIs were mapped to T2-weighted MRI (T2w), apparent diffusion coefficient (ADC), and T1 and T2 MRF maps. Their correlations with TCRs were computed using Pearson's correlation coefficient (R). Statistically significant differences in means were assessed using one-way ANOVA.

RESULTS

Statistically significant differences (p < 0.01) in means of TCRs and T1 and T2 MRF were observed between PCa, prostatitis, and normal PZ. A negative correlation was observed between T1 and T2 MRF and epithelium (R = - 0.38, - 0.44, p < 0.05) of PCa. T1 MRF was correlated in opposite directions with stroma of PCa and prostatitis (R = 0.35, - 0.44, p < 0.05). T2 MRF was positively correlated with lumen of PCa and prostatitis (R = 0.57, 0.46, p < 0.01). Mean T2 MRF showed significant differences (p < 0.01) between PCa and prostatitis across both transition zone (TZ) and PZ, while mean T1 MRF was significant (p = 0.02) in TZ.

CONCLUSION

Significant associations between MRF (T1 in the TZ and T2 in the PZ) and tissue compartments on corresponding histopathology were observed.

KEY POINTS

• Mean T2 MRF measurements and ADC within cancerous regions of interest dropped with increasing ISUP prognostic groups (IPG). • Mean T1 and T2 MRF measurements were significantly different (p < 0.001) across IPGs, prostatitis, and normal peripheral zone (NPZ). • T2 MRF showed stronger correlations in the peripheral zone, while T1 MRF showed stronger correlations in the transition zone with histopathology for prostate cancer.

Multiparametric Magnetic Resonance Imaging Alone is Insufficient to Detect Grade Reclassification in Active Surveillance for Prostate Cancer

Multiparametric magnetic resonance imaging (mpMRI) has improved the detection of clinically significant prostate cancer. It remains unclear, however, whether mpMRI can safely replace confirmatory or surveillance biopsies in men with low-risk disease managed with active surveillance (AS). Overall, 166 men were upgraded at a median of 29 mo (interquartile range 13-54). The overall negative predictive value (NPV) of mpMRI was 79.5% and ranged from 74.4% to 84.6% for all AS biopsies up to the fourth surveillance biopsy. In men with prostate-specific antigen density ≥0.15 ng/ml/cm³, the overall NPV of mpMRI was 65.5% and ranged from 57.1% to 73.3% across serial mpMRI scans. These findings support the hypothesis that mpMRI is helpful but insufficient to rule out pathological reclassification, especially at confirmatory biopsy or in the presence of other risk factors. PATIENT SUMMARY: Multiparametric magnetic resonance imaging (mpMRI) alone misses a considerable percentage of clinically significant prostate cancers (Gleason grade group ≥2) in men on active surveillance for low-risk prostate cancer. We conclude that mpMRI alone cannot safely replace surveillance prostate biopsies, particularly at confirmatory biopsy or in the presence of other risk factors.

Value of systematic sampling in an mp-MRI targeted prostate biopsy strategy

The clinical utility of systematic prostate biopsy in addition to multi-parametric magnetic resonance imagining (mp-MRI) targeted biopsy pathways remains unclear. Despite radiological advancements in mp-MRI and utilisation of international standardised reporting systems (i.e., PI-RADS, LIKERT), undetected clinically significant prostate cancer (csPCa) on imaging persists. This has prevented the widespread adoption of an exclusively targeted biopsy approach. The current evidence on csPCa cancer detection rates in mp-MRI targeted alone and combined with a non-targeted systematic sampling is presented. Arguments for and against routine limited systematic sampling as an adjunct to an mp-MRI targeted biopsy are discussed. Our review will report the clinical utility of a combined sampling strategy on csPCa detection rate. The available evidence suggests that we are yet to reach a stage where non-targeted systematic prostate biopsy can be routinely omitted in mp-MRI targeted prostate biopsy pathways. Research should focus on improving the accuracy of mp-MRI, prostate biopsy techniques, and in identifying those men that will most benefit from a combined prostate biopsy. Such strategies may help future urologists reduce the burden of non-targeted cores in modern mp-MRI prostate biopsy pathways.

Can Focal Therapy Replace Radical Therapy for Prostate Cancer? Against Focal Therapy

Until prospective data demonstrate the oncologic efficacy of focal therapy for clinically significant, localized prostate cancer, it should be considered as experimental and only performed within the confines of a clinical trial.

Targeted Prostate Biopsy in the Era of Active Surveillance

Targeted prostate biopsy using magnetic resonance imaging (MRI) guidance is improving the accuracy of prostate cancer (CaP) diagnosis. This new biopsy technology is especially important for men undergoing active surveillance, improving patient selection for enrollment and enabling precise longitudinal monitoring. Magnetic resonance imaging/ultrasound fusion biopsy allows for 3 functions not previously possible with US-guided biopsy: targeting of suspicious regions, template-mapping for systematic sampling, and tracking of cancer foci over time. This article reviews the evolving role of the new biopsy methods in active surveillance, including the UCLA Active Surveillance pathway, which has incorporated magnetic resonance imaging/ultrasound fusion biopsy from program inception as a possible model.

Future Perspectives and Challenges of Prostate MR Imaging

MR imaging is an important part of prostate cancer diagnosis. Variations in quality and skill in general practice mean results are not as impressive as they were in academic centers. This observation provides an impetus to improve the method. Improved quality assurance will likely result in better outcomes. Improved characterization of clinically significant prostate cancer may assist in making MR imaging more useful. Improved methods of registering MR imaging with transrectal ultrasound imaging and robotic arms controlling the biopsy can reduce the impact of inexperienced operators and make the entire system of MR imaging-guided biopsies more robust.