How Would MRI-targeted Prostate Biopsy Alter Radiation Therapy Approaches in Treating Prostate Cancer?

Risk stratification for early biochemical recurrence of prostate cancer in the era of multiparametric magnetic resonance imagining-targeted biopsy

BACKGROUND

Multiparametric magnetic resonance imaging (MRI) and MRI-targeted biopsy are nowadays recommended in the prostate cancer (PCa) diagnostic pathway. Ploussard and Mazzone have integrated these tools into novel risk classification systems predicting the risk of early biochemical recurrence (eBCR) in PCa patients who underwent radical prostatectomy (RP). We aimed to assess available risk classification systems and to define the best-performing.

METHODS

Data on 1371 patients diagnosed by MRI-targeted biopsy and treated by RP between 2014 and 2022 at eight European tertiary referral centers were analyzed. Risk classifications systems included were the European Association of Urology (EAU) and National Comprehensive Cancer Network (NCCN) risk groups, the Cancer of the Prostate Risk Assessment (CAPRA) score, the International Staging Collaboration for Cancer of the Prostate (STAR-CAP) classification, the Ploussard and Mazzone models, and ISUP grade group. Kaplan-Meier analyses were used to compare eBCR among risk classification systems. Performance was assessed in terms of discrimination quantified using Harrell's c-index, calibration, and decision curve analysis (DCA).

RESULTS

Overall, 152 (11%) patients had eBCR at a median follow-up of 31 months (interquartile range: 19-45). The 3-year eBCR-free survival rate was 91% (95% confidence interval [CI]: 89-93). For each risk classification system, a significant difference among survival probabilities was observed (log-rank test p < 0.05) except for NCCN classification (p = 0.06). The highest discrimination was obtained with the STAR-CAP classification (c-index 66%) compared to CAPRA score (63% vs. 66%, p = 0.2), ISUP grade group (62% vs. 66, p = 0.07), Ploussard (61% vs. 66%, p = 0.003) and Mazzone models (59% vs. 66%, p = 0.02), and EAU (57% vs. 66%, p < 0.001) and NCCN (57% vs. 66%, p < 0.001) risk groups. Risk classification systems demonstrated good calibration characteristics. At DCA, the CAPRA score showed the highest net benefit at a probability threshold of 9%-15%.

CONCLUSIONS

The performance of risk classification systems using MRI and MRI-targeted information was less optimistic when tested in a contemporary set of patients. CAPRA score and STAR-CAP classification were the best-performing and should be preferred for treatment decision-making.

Magnetic Resonance Imaging-Targeted Biopsy and Pretherapeutic Prostate Cancer Risk Assessment: a Systematic Review: Biopsie ciblée par Imagerie par résonance magnétique et évaluation pré-thérapeutique du risque de cancer de la prostate : revue systématique

INTRODUCTION

Multiparametric magnetic resonance imaging (MRI) has been included in prostate cancer (PCa) diagnostic pathway and may improve disease characterization. The aim of this systematic review is to assess the added value of MRI-targeted biopsy (TB) in pre-therapeutic risk assessment models over existing tools based on systematic biopsy (SB) for localized PCa.

EVIDENCE ACQUISITION

A systematic search was conducted using Pubmed (Medline), Scopus and ScienceDirect databases according to Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement. We included studies through October 2021 reporting on TB in pretherapeutic risk assessment models.

EVIDENCE SYNTHESIS

We identified 24 eligible studies including 24'237 patients for the systematic review. All included studies were retrospective and conducted in patients undergoing radical prostatectomy. Nine studies reported on the risk of extraprostatic extension, seven on the risk of lymph node invasion, three on the risk of biochemical recurrence and nine on the improvement of PCa risk stratification. Overall, the combination of TB with imaging, clinical and biochemical parameters outperformed current pretherapeutic risk assessment models. External validation studies are lacking for certain endpoints and the absence of standardization among TB protocols, including number of TB cores and fusion systems, may limit the generalizability of the results.

CONCLUSION

TB should be incorporated in pretherapeutic risk assessment models to improve clinical decision making. Further high-quality studies are required to determine models' generalizability while there is an urgent need to reach consensus on a standardized TB protocol. Long-term outcomes after treatment are also awaited to confirm the superiority of such models over classical risk classifications only based on SB. © 2022 Elsevier Masson SAS. All rights reserved.

The prognostic value of high-grade prostate cancer pattern on MRI-targeted biopsies: predictors for downgrading and importance of concomitant systematic biopsies

PURPOSE

To assess the proportion and risk factors for downgrading and reclassification to favorable disease in patients having high-grade (HG) prostate cancer (PCa) pattern on magnetic resonance imaging (MRI)-targeted-biopsy (TB).

METHODS

From a radical prostatectomy (RP) cohort, we included patients with pre-biopsy positive MRI and HG [defined by Grade Group (GG) ≥ 3] PCa on MRI-TB. All patients also underwent concomitant systematic biopsy (SB). The main endpoints were the rates of downgrading to GG2, overall downgrading, favorable disease (pT2 and GG2) on RP specimens, and biochemical recurrence-free-survival (RFS). We studied the correlations between HG on concomitant SB, final pathological outcomes and biochemical RFS curves.

RESULTS

Overall downgrading, downgrading to GG2 disease and favorable disease were noted in 36.2%, 24.1%, and 15.4% respectively. HG on concomitant SB was correlated with pT3-4 disease (p < 0.001), pN1 disease (p < 0.001), positive surgical margins (p = 0.043), PSA recurrence (p = 0.003). In multivariable analysis, the presence of GG4-5 on TB (p = 0.013; OR 0.263) and the presence of HG on concomitant SB (p = 0.010; OR 0.269) were negatively and independently correlated with the risk of downgrading to GG2. The presence of HG on concomitant SB independently predicted RFS with a hazard ratio of 2.173 (p = 0.049; 95% CI 1.005-4.697).

CONCLUSIONS

Our data shows that a limited HG restricted to TB can often be associated with a favorable grade in almost a quarter of the cases and downgraded in almost half of the cases. Detailed SB features, mainly the presence of HG on concomitant SB, was associated with a more accurate pathology and oncologic outcomes prediction, pleading for the maintenance of SB in MRI-positive patients.

Decreased accuracy of the prostate cancer EAU risk group classification in the era of imaging-guided diagnostic pathway: proposal for a new classification based on MRI-targeted biopsies and early oncologic outcomes after surgery

PURPOSE

To assess the performance of EAU risk classification in PCa patients according to the biopsy pathway (standard versus MRI guided) and to develop a new, more accurate, targeted biopsy (TB)-based classification.

MATERIALS AND METHODS

We included 1345 patients consecutively operated by radical prostatectomy (RP) since 2014, when MRI and TB were introduced in the diagnostic pathway. Patients underwent systematic biopsy (SB) only (n = 819) or SB and TB (n = 526) prior to RP during the same time period. Pathological and biochemical outcomes were compared between PCa men undergoing SB (SB cohort) and a combination of TB and SB (TB cohort). Kaplan-Meier and Cox regression models were used to assess biochemical recurrence-free survival (RFS).

RESULTS

Both cohorts were comparable regarding final pathology and RFS (p = 0.538). The EAU risk classification accurately predicted outcomes in SB cohort, but did not significantly separate low from intermediate risk in TB cohort (p = 0.791). In TB cohort, the new proposed three-group risk classification significantly improved the recurrence risk prediction compared with the EAU risk classification: HR 4 (versus HR 1.2, p = 0.009) for intermediate, and HR 15 (versus HR 6.5, p < 0.001) in high-risk groups, respectively. A fourth group defining very high-risk cases (≥ T2c clinical stage or grade group 5) was also proposed.

CONCLUSIONS

The new classification integrating TB findings we propose meaningfully improves the recurrence prediction after surgery in patients undergoing a TB-based diagnostic pathway, compared with standard EAU risk classification which is still relevant for patients undergoing only SB. External validation is needed.

Quantitative 3T multiparametric MRI of benign and malignant prostatic tissue in patients with and without local recurrent prostate cancer after external-beam radiation therapy

Background

Post‐radiotherapy locally recurrent prostate cancer (PCa) patients are candidates for focal salvage treatment. Multiparametric MRI (mp‐MRI) is attractive for tumor localization. However, radiotherapy‐induced tissue changes complicate image interpretation. To develop focal salvage strategies, accurate tumor localization and distinction from benign tissue is necessary.

Purpose

To quantitatively characterize radio‐recurrent tumor and benign radiation‐induced changes using mp‐MRI, and investigate which sequences optimize the distinction between tumor and benign surroundings.

Study Type

Prospective case–control.

Subjects

Thirty‐three patients with biochemical failure after external‐beam radiotherapy (cases), 35 patients without post‐radiotherapy recurrent disease (controls), and 13 patients with primary PCa (untreated).

Field Strength/Sequences

3T; quantitative mp‐MRI: T₂‐mapping, ADC, and K^trans and k_ep maps.

Assessment

Quantitative image‐analysis of prostatic regions, within and between cases, controls, and untreated patients.

Statistical Tests

Within‐groups: nonparametric Friedman analysis of variance with post‐hoc Wilcoxon signed‐rank tests; between‐groups: Mann–Whitney tests. All with Bonferroni corrections. Generalized linear mixed modeling to ascertain the contribution of each map and location to tumor likelihood.

Results

Benign imaging values were comparable between cases and controls (P = 0.15 for ADC in the central gland up to 0.91 for k_ep in the peripheral zone), both with similarly high peri‐urethral K^trans and k_ep values (min⁻¹) (median [range]: K^trans = 0.22 [0.14–0.43] and 0.22 [0.14–0.36], P = 0.60, k_ep = 0.43 [0.24–0.57] and 0.48 [0.32–0.67], P = 0.05). After radiotherapy, benign central gland values were significantly decreased for all maps (P ≤ 0.001) as well as T₂, K^trans, and k_ep of benign peripheral zone (all with P ≤ 0.002). All imaging maps distinguished recurrent tumor from benign peripheral zone, but only ADC, K^trans, and k_ep were able to distinguish it from benign central gland. Recurrent tumor and peri‐urethral K^trans values were not significantly different (P = 0.81), but k_ep values were (P < 0.001). Combining all quantitative maps and voxel location resulted in an optimal distinction between tumor and benign voxels.

Data Conclusion

Mp‐MRI can distinguish recurrent tumor from benign tissue.

Level of Evidence: 2

Technical Efficacy Stage: 2

J. Magn. Reson. Imaging 2019;50:269–278.