Repeat MRI during active surveillance: natural history of prostatic lesions and upgrading rates

Role of MRI in Active Surveillance of Prostate Cancer

Magnetic resonance imaging (MRI) plays an important role in the management of patients with prostate cancer on active surveillance. In this review, we will explore the incorporation of MRI into active surveillance protocols, detailing its impact on clinical decision-making and patient management and discussing how it aligns with current guidelines and practice patterns. The role of MRI in this patient population continues to evolve over time, and we will discuss some of the recent advancements in the field and highlight potential areas for future research endeavors.

2023/2024 update of the national prostate cancer guidelines in Sweden

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MRI and active surveillance: thoughts from across the pond

In the United States (US), urological guidelines recommend active surveillance (AS) for patients with low-risk prostate cancer (PCa) and endorse it as an option for those with favorable intermediate-risk PCa with a > 10-year life expectancy. Multiparametric magnetic resonance imaging (mpMRI) is being increasingly used in the screening, monitoring, and staging of PCa and involves the combination of T2-weighted, diffusion-weighted, and dynamic contrast-enhanced T1-weighted imaging. The American Urological Association (AUA) guidelines provide recommendations about the use of mpMRI in the confirmatory setting for AS patients but do not discuss the timing of follow-up mpMRI in AS. The National Comprehensive Cancer Network (NCCN) discourages using it more frequently than every 12 months. Finally, guidelines state that mpMRI can be used to augment risk stratification but should not replace periodic surveillance biopsy. In this review, we discuss the current literature regarding the use of mpMRI for patients with AS, with a particular focus on the approach in the US. Although AS shows a benefit to the addition of mpMRI to diagnostic, confirmatory, and follow-up biopsy, there is no strong evidence to suggest that mpMRI can safely replace biopsy for most patients and thus it must be incorporated into a multimodal approach. CLINICAL RELEVANCE STATEMENT: According to the US guidelines, regular follow-ups are important for men with prostate cancer on active surveillance, and prostate MRI is a valuable tool that should be utilized, in combination with PSA kinetics and biopsies, for monitoring prostate cancer. KEY POINTS: According to the US guidelines, the addition of MRI improves the detection of clinically significant prostate cancer. Timing interval imaging of patients on active surveillance remains unclear and has not been specifically addressed. MRI should trigger further work-ups, but not replace periodic follow-up biopsies, in men on active surveillance.

Transcript Markers from Urinary Extracellular Vesicles for Predicting Risk Reclassification of Prostate Cancer Patients on Active Surveillance

Serum prostate-specific antigen (PSA), its derivatives, and magnetic resonance tomography (MRI) lack sufficient specificity and sensitivity for the prediction of risk reclassification of prostate cancer (PCa) patients on active surveillance (AS). We investigated selected transcripts in urinary extracellular vesicles (uEV) from PCa patients on AS to predict PCa risk reclassification (defined by ISUP 1 with PSA > 10 ng/mL or ISUP 2-5 with any PSA level) in control biopsy. Before the control biopsy, urine samples were prospectively collected from 72 patients, of whom 43% were reclassified during AS. Following RNA isolation from uEV, multiplexed reverse transcription, and pre-amplification, 29 PCa-associated transcripts were quantified by quantitative PCR. The predictive ability of the transcripts to indicate PCa risk reclassification was assessed by receiver operating characteristic (ROC) curve analyses via calculation of the area under the curve (AUC) and was then compared to clinical parameters followed by multivariate regression analysis. ROC curve analyses revealed a predictive potential for AMACR, HPN, MALAT1, PCA3, and PCAT29 (AUC = 0.614-0.655, p < 0.1). PSA, PSA density, PSA velocity, and MRI maxPI-RADS showed AUC values of 0.681-0.747 (p < 0.05), with accuracies for indicating a PCa risk reclassification of 64-68%. A model including AMACR, MALAT1, PCAT29, PSA density, and MRI maxPI-RADS resulted in an AUC of 0.867 (p < 0.001) with a sensitivity, specificity, and accuracy of 87%, 83%, and 85%, respectively, thus surpassing the predictive power of the individual markers. These findings highlight the potential of uEV transcripts in combination with clinical parameters as monitoring markers during the AS of PCa.

Annual mpMRI surveillance: PI-RADS upgrading and increasing trend correlated with patients who harbor clinically significant disease

INTRODUCTION

Prostate cancer screening has routinely identified men with very low- or low-risk disease, per the National Comprehensive Cancer Network guidelines. Current literature has demonstrated that the most appropriate management strategy for these patients is active surveillance (AS). The mainstay of AS includes periodic biopsies and biannual prostate-specific antigen tests. However, multiparametric magnetic resonance imaging (mpMRI) is uniquely posed to improve patient surveillance. This study aimed to evaluate the utility of an annual mpMRI in patients on AS, focusing on radiologic upgrading and Prostate Imaging-Reporting and Data System (PI-RADS) trends as indicators of clinically significant disease.

METHODS

This prospective, single intuition, study enrolled 208 patients on AS who had at least two biopsies and 1 mpMRI with a median follow-up of 5.03 years. The main outcome variable was time to Gleason grade (GG) reclassification.

RESULTS

After delineating patients on their initial PI-RADS score, men with score 3 and 5 lesions at first MRI had comparable GG reclassification-free survival to their counterparts. Conversely, men with initial PI-RADS 4 lesions showed a lower 5-year GG reclassification-free survival compared to those with PI-RADS score 1-2. The cohort was then subset to 70 patients who obtained ≥2 mpMRIs on protocol. Men experiencing uptrending mpMRI scores had an increased risk of GG reclassification, with a 35.4% difference in 5 year GG reclassification-free survival probability on the Kaplan-Meier curve analysis.

CONCLUSION

In conclusion, this study demonstrates that for men on AS with stable recapitulated disease, an annual MRI may replace repeat biopsies after confirmatory sampling has been obtained. On the other hand, men who initiate AS with PI-RADS 4 and/or who display uptrending mpMRI scores require periodic biopsies along with repeat imaging. This study highlights the utility of integrating an annual MRI into AS protocols, thus promising a more effective approach to management.

Conditional survival of patients with low-risk prostate cancer: Temporal changes in active surveillance permanence over time

PURPOSE

To determine risk categories for patients with prostate cancer (PCa) in active surveillance (AS) and to test the conditional survival (CS) that examined the effect of event-free survival since AS-entrance.

MATERIALS AND METHODS

From January 2012 to December 2020 we analyzed 606 patients with PCa enrolled in our AS program. Kaplan-Meier (KM) plots depicted AS-exit rate. Multivariable Cox regression models (MCRMs) tested for AS-exit rate independent predictors to determine risk categories. CS estimates were used to calculate overall AS-exit rate after event-free survival intervals of 1, 2, 3, and 5 years, and after stratification according to risk categories.

RESULTS

At MCRMs PSAd ≥ 0.15 (HR: 1.43; P-value 0.04), PI-RADS 4-5 (HR: 2.56; P-value <0.001) and number of biopsy positive cores ≥ 2 (HR: 1.75; P-value <0.001) were independent predictors of AS-exit. These variables were used to determine risk categories: low-, intermediate- and high-risk. Overall, according to CS-analyses, 5-year AS-exit free rate increased from 59.7% at baseline, to 67.3%, 74.7%, and 89.4% in patients who remained in AS respectively ≥1, ≥2, ≥3 and ≥5 years. After stratification according to risk categories, in those patients who remained in AS ≥ 5 years, 5-year AS-exit free rates increased from 76.3% to 100% in patients with a low-risk, from 62.7% to 83.7% in patients with an intermediate-risk and from 42.3% to 87.5% in patients with a high-risk.

CONCLUSIONS

CS models showed a direct relationship between event-free survival duration and subsequent AS permanence in overall PCa patients and after stratification according to risk categories.