Emerging and anticipated innovations in prostate cancer MRI and their impact on patient care

Prostate cancer (PCa) remains the leading malignancy affecting men, with over 3 million men living with the disease in the US, and an estimated 288,000 new cases and almost 35,000 deaths in 2023 in the United States alone. Over the last few decades, imaging has been a cornerstone in PCa care, with a crucial role in the detection, staging, and assessment of PCa recurrence or by guiding diagnostic or therapeutic interventions. To improve diagnostic accuracy and outcomes in PCa care, remarkable advancements have been made to different imaging modalities in recent years. This paper focuses on reviewing the main innovations in the field of PCa magnetic resonance imaging, including MRI protocols, MRI-guided procedural interventions, artificial intelligence algorithms and positron emission tomography, which may impact PCa care in the future.

Functional outcomes and safety of focal therapy for prostate cancer: a systematic review on results and patient-reported outcome measures (PROMs)

INTRODUCTION

Focal therapy (FT) is a promising alternative with curative intent for Low- to Intermediate-risk localized Prostate Cancer (PCa), claiming better functional outcomes and safety profile than standard whole-gland treatments. Ten different FT modalities have been described in the literature. The objective of our narrative review is to evaluate the safety profile and functional outcomes of these different modalities and the current most used tools of assessment for those outcomes.

MATERIAL AND METHODS

Literature search was performed on 21st February 2023 using PubMed, EMBASE, and Scopus, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement (PRISMA). Articles reporting whole-gland treatments were excluded. All articles reporting functional outcomes were included.

RESULTS

One-hundred-seven studies, reporting data on 6933 patients, were included (26 on High Intensity Focal Ultrasound, 22 on Focal Cryotherapy, 14 on Irreversible Electroporation, 11 on Focal brachytherapy, 10 on Focal Laser Ablation, 8 on Photodynamic Therapy, 3 on Microwave ablation, 3 on Robotic Partial Prostatectomy, 2 on bipolar Radio Frequency Ablation, 1 on Prostatic Artery Embolization, and 7 studies comparing different FTs). Post-operative pad-free rate ranged between 92.3-100%. Greater heterogeneity exists considering the Change in Erectile Function, with Changing in Erectile function- rates ranging between 0-94.4% (Cryotherapy). The most used Patient-Reported Outcome Measures (PROMs) were the International Prostate Symptom Score and the International Index of Erectile Function for incontinence/urinary function and potency, respectively. The most common reported complications were hematuria, infections, and urethral strictures, with rates widely ranging among different treatments. The Clavien-Dindo Classification was the most used (40/88 papers) to describe adverse events.

CONCLUSION

FT is a promising treatment for localized PCa, achieving excellent results in terms of safety and functional outcomes. There is a wide heterogeneity in the definition of PROMS and time of collection between studies. High quality comparative studies with standard treatments are needed to reinforce these findings.

Focal Therapy for Prostate Cancer: The Impact on Sexual Function

Focal therapy (FT) has emerged as a potential treatment for localized prostate cancer (PCa) with encouraging functional outcomes. According to the compelling evidence based on meta-analyses and recent trials, erectile function (EF) is mostly retained at 6 and 12 months after FT when compared to baseline. These findings are consistent across different energy sources reported to date. However, overall, quality of life, including impotence, was not the endpoint for most studies. Additionally, impotency has not been consistently reported in most of the recent literature. Furthermore, confounding factors such as baseline potency and usage of phosphodiesterase 5 inhibitors (PDE5-I) were also frequently undisclosed. Long-term functional outcomes are awaited. To fully comprehend how FT affects EF, more extensive long-term randomized clinical trials using EF as a primary outcome are needed.

Estimation of porcine pancreas optical properties in the 600-1100 nm wavelength range for light-based therapies

This work reports the optical properties of porcine pancreatic tissue in the broad wavelength range of 600–1100 nm. Absorption and reduced scattering coefficients (µ_a and µ_s′) of the ex vivo pancreas were obtained by means of Time-domain Diffuse Optical Spectroscopy. We have investigated different experimental conditions—including compression, repositioning, spatial sampling, temporal stability—the effect of the freezing procedure (fresh vs frozen-thawed pancreas), and finally inter-sample variability. Good repeatability under different experimental conditions was obtained (median coefficient of variation less than 8% and ~ 16% for µ_a and µ_s′, respectively). Freezing–thawing the samples caused an irreversible threefold reduction of µ_s′ and no effect on µ_a. The absorption and reduced scattering spectra averaged over different samples were in the range of 0.12–0.74 cm⁻¹ and 12–21 cm⁻¹ with an inter-sample variation of ~ 10% and ~ 40% for µ_a and µ_s′, respectively. The calculated effective transport coefficient (µ_eff) for fresh pancreatic tissue shows that regions between 800–900 nm and 1050–1100 nm are similar and offer the lowest tissue attenuation in the considered range (i.e., µ_eff ranging from 2.4 to 2.7 cm⁻¹). These data, describing specific light-pancreas interactions in the therapeutic optical window for the first time, provide pivotal information for planning of light-based thermotherapies (e.g., laser ablation) and instruction of light transport models for biophotonic applications involving this organ.

Laser technology in urologic oncology

Laser technology has been used in Urology since the 80s with a lot of different applications in endoscopic and open surgery. With the developments of the technology and the introduction of new active medium and source of laser energy, this technology have become the gold standard not only in stone surgery but even in benign prostate enlargement (BPE) surgical treatment. Regarding urologic oncology, laser energy has now reached an important role in focal therapy and in conservative treatment. The possibility of having better functional outcomes without any relevant impact on oncological results led to an increased use of laser in penile surgery, with a significant mention in urological guidelines for this option. In urothelial cancers as well, both in conservative management of upper tract tumors that in the treatment of non muscle invasive bladder cancer, a clear role of these relatively new source of energy have been demonstrated. Finally, both in prostate that in renal cancer the strategy of focal therapy may take advantage from this precise and fine technology. In this review we analyzed and described the applications of laser energy in urological cancers with a specific focus on penile, urothelial and prostate cancer.

Focal prostate cancer therapy in the era of multiparametric MRI: a review of options and outcomes

BACKGROUND

The goal of prostate cancer focal therapy is to achieve oncologic control while reducing the rate of adverse events associated with whole-gland treatments. Numerous focal therapy modalities are currently available with early data demonstrating highly variable rates of cancer control and preservation of sexual/urinary function.

METHODS

All English language clinical trial publications evaluating various focal therapies for localized prostate cancer were reviewed. The literature search was limited to studies from the modern era of MRI-guided treatment, as MRI is hypothesized to improve tumor localization and targeting. Primary outcomes were post-treatment cancer-free rates, in-field/out-of-field recurrence rates, and rates of conversion to radical therapy. Secondary outcomes were related to functional status and adverse events.

RESULTS

Numerous focal therapies were identified with clinical data including high-intensity focused ultrasound, transurethral ultrasound ablation, focal laser ablation, focal cryotherapy, irreversible electroporation, and photodynamic therapy. Recurrence rates among all technologies were low to moderate (0-51%) and rates of freedom from radical treatment were highly variable (46-98%). Rates of erectile dysfunction and incontinence generally ranged from 0 to 44% and 0 to 12%, respectively, with variability between focal therapy modalities. Caution should be exercised when comparing studies as outcomes are strongly associated with patient selection. No individual focal therapy is currently recommended by society guidelines. Randomized controlled trials are ongoing in search of a standard of care.

CONCLUSION

For localized MRI-visible prostate cancer, early clinical trial data demonstrate that focal therapy can provide good to moderate cancer control while having preferable side effect profiles compared to whole-gland treatments. While current studies do not make head-to-head comparisons between technologies, early data suggest a potential for these technologies to provide adequate cancer control in a well-selected patient population. The oncologic outcomes of some focal therapies appear promising; however, longer-term follow-up data are needed to assess the durability of early outcomes.

Current evidence for focal laser ablation and vascular-targeted photodynamic therapy for localized prostate cancer: review of literature published in the last 2 years

PURPOSE OF REVIEW

Currently, a significant number of patients are diagnosed with unilateral and apparently unifocal low or intermediate-risk prostate cancer (PCa). These patients are suitable for focal therapy, thus preventing radical treatment side effects without affecting cancer control. Among focal therapy energy sources, laser-based technologies have shown promising outcomes. We aimed to summarize recent data on focal laser ablation (FLA) and vascular-targeted photodynamic therapy (VTP) for PCa.

RECENT FINDINGS

We selected eight studies reporting data on 1155 patients with PCa who underwent laser-based focal therapy. Five studies were on FLA and three on VTP (six prospective and two retrospective series); four reported both oncologic and functional outcomes whereas in three only oncologic and one only functional outcomes were discussed. Follow-up protocols and durations varied widely among the studies. PCa recurrence rates ranged between 20 and 56%. Urinary and erectile function were preserved after treatment, and complications were mild and transient. A lack of high-quality data on long-term oncological outcomes still remains, thus further highlighting the need for prospective controlled studies.

SUMMARY

FLA and VTP are well tolerated procedures with excellent functional outcomes. However, both procedures showed a significant rate of PCa recurrence, thus demonstrating a certain grade of oncologic control failure of the procedure and/or nonoptimal patients' selection.

MR Imaging in Real Time Guiding of Therapies in Prostate Cancer

Magnetic resonance imaging (MRI)-guided therapy for prostate cancer (PCa) aims to reduce the treatment-associated comorbidity of existing radical treatment, including radical prostatectomy and radiotherapy. Although active surveillance has been used as a conservative method to reduce overtreatment, there is a growing demand for less morbidity and personalized (focal) treatment. The development of multiparametric MRI was of real importance in improving the detection, localization and staging of PCa. Moreover, MRI has been useful for lesion targeting within the prostate, as it is used in the guidance of prostate biopsies, by means of cognitive registration, MRI-ultrasound fusion guidance or direct in-bore MRI-guidance. With regard to PCa therapies, MRI is used for precise probe placement into the lesion and to accurately monitor the treatment in real-time. Moreover, advances in MR-compatible thermal ablation allow for noninvasive real-time temperature mapping during treatment. In this review, we present an overview of the current status of MRI-guided therapies in PCa, focusing on cryoablation, focal laser ablation, high intensity focused ultrasound and transurethral ultrasound ablation. We explain the important role of MRI in the evaluation of the completeness of the ablation and during follow-up. Finally, we will discuss the challenges and future development inherent to these new technologies.

Preclinical evaluation of a clinical prototype transrectal diffuse optical tomography system for monitoring photothermal therapy of focal prostate cancer

SIGNIFICANCE

Our work demonstrates in preclinical models that continuous-wave transrectal diffuse optical tomography (TRDOT) can be used to accurately monitor photothermal therapy (PTT) and, in particular, the progression of the photocoagulation boundary toward the rectum. When used in patients, this should prevent rectal damage during PTT, thereby achieving maximum treatment efficacy while ensuring safety, using a technology platform suitable for wide dissemination.

AIM

We aim to validate that TRDOT measurements analyzed using a shape-based image-reconstruction algorithm (SBDOT) allow localization of the photocoagulation boundary during PTT within ±1  mm toward the rectum in the transverse plane.

APPROACH

TRDOT measurements were performed in tissue-simulating phantoms, ex vivo tissues, and an in vivo canine prostate model. The accuracy and sensitivity of reconstructing the size and location of the coagulation zone were determined, based on changes in the tissue absorption and reduced scattering coefficients upon photocoagulation. The reconstruction also yields the native and coagulated tissue optical properties.

RESULTS

The TRDOT measurements and SBDOT reconstruction algorithm were confirmed to perform sufficiently well for clinical translation in PTT monitoring, recovering the location of the coagulation boundary within ±1  mm compared to the true value as determined by direct visualization postexcision and/or MRI.

CONCLUSIONS

Implementing previously described TRDOT instrumentation and SBDOT image reconstruction in different tissue models confirms the potential for clinincal translation, including required refinements of the system and reconstruction algorithm.

Detailing Sexual Outcomes After Focal Therapy for Localised Prostate Cancer: A Systematic Review and Meta-analysis

CONTEXT

Focal therapy has emerged as a promising option to treat well-selected men with localised prostate cancer while preserving healthy prostate tissue and key structures, such as the urethral sphincter and neurovascular bundles. However, how this tissue preservation may translate into improved outcomes, particularly into improved sexual outcomes, is still an active research field.

OBJECTIVE

We conducted a systematic review and meta-analysis of the literature to summarise the existing evidence, in order to provide patients with updated data on what to expect after treatment and help identify gaps in current knowledge that may warrant future research.

EVIDENCE ACQUISITION

A systematic literature search was conducted on Medline, EMBASE, Scopus, and Web of Science. The search strategy was defined using the "litsearchr" function in R based on a preliminary "naïve" search using the following terms on Medline: (("focal therapy" OR "focal treatment") AND ("prostate cancer") AND ("sexual function" OR "erectile function")). A total of 42 studies, comprising 3117 patients treated and 2352 with available sexual outcomes, were included in the qualitative data synthesis and 26 in a random-effect meta-analysis.

EVIDENCE SYNTHESIS

The five-item International Index of Erectile Function (IIEF-5) was the most frequently used questionnaire (30/42 studies), with completion rates ranging from 24% to 100% at 18-24 mo. A decrease was noted at 3 mo (IIEF-5 decrease estimate -3.70 [95% confidence interval -4.43, -2.96]), with improvements at 6 mo (-2.18 [-2.91, -1.46]) and 12 mo (-2.14 [-2.96, -1.32]). Studies in which patients had an altered baseline sexual function were more likely to report a significant and durable postoperative decrease in erectile function scores. The patient-reported outcome questionnaires used were not designed for a diverse population. Functional outcomes were not the primary endpoint and have not been reported consistently in most studies considered.

CONCLUSIONS

Focal therapy led to changes in erectile function in most cases under the significance threshold of the patient-reported outcome questionnaires used. However, patients should be counselled according to their baseline erectile function. More research is warranted to detail aspects other than erectile function, such as ejaculation or orgasm. The early postoperative period appears key to study sexual changes after focal therapy, while only a moderate decrease is expected at 12 mo.

PATIENT SUMMARY

We reviewed the published literature detailing the sexual consequences of focal therapy for localised prostate cancer using patient-reported outcome questionnaires. Patients were likely to describe a significant decrease in their erectile function at 3 mo, with improvements noted at 6 and 12 mo. The results obtained may not be reproducible in a more diverse population, and further research is warranted to better study aspects other than erectile function, such as ejaculation or orgasm.

An Updated Systematic Review on Focal Therapy in Localized Prostate Cancer: What Has Changed over the Past 5 Years?

CONTEXT

Focal therapy is a promising, minimally invasive strategy to selectively treat localized prostate cancer. A previous systematic review indicated that there is growing evidence for favorable functional outcomes, but that oncological effectiveness was yet to be defined.

OBJECTIVE

To assess the effectiveness of focal therapy in patients with localized prostate cancer in terms of functional and oncological outcomes.

EVIDENCE ACQUISITION

PubMed, Embase, and The Cochrane Library were searched for studies between October 2015 and December 31, 2020. In addition, the research stages were acquired according to the Idea, Development, Exploration, Assessment, Long-term study (IDEAL) recommendations. Ongoing studies were identified through clinical trial registries.

EVIDENCE SYNTHESIS

Seventy-two studies were identified exploring eight different sources of energy to deliver focal therapy in 5827 patients. Twenty-seven studies reported on high-intensity focused ultrasound (HIFU), nine studies on irreversible electroporation, 11 on cryoablation, eight on focal laser ablation and focal brachytherapy, seven on photodynamic therapy (PDT), two on radiofrequency ablation, and one on prostatic artery embolization. The majority of studies were prospective development stage 2a studies (n = 35). PDT and HIFU, both in stage 3, showed promising results. Overall, HIFU studies reported a median of 95% pad-free patients and a median of 85% patients with no clinically significant cancer (CSC) in the treated area. For PDT, no changes in continence were reported and a median of 90% of patients were without CSC. Both treatments were well tolerated.

CONCLUSIONS

Over the past 5 yr, focal therapy has been studied for eight different energy sources, mostly in single-arm stage 2 studies. Although a first randomized controlled trial in focal therapy has been performed, more high-quality evaluations are needed, preferably via multicenter randomized controlled trials with long-term follow-up and predefined assessment of oncological and functional outcomes and health-related quality-of-life measures.

PATIENT SUMMARY

Focal treatment (FT) of prostate cancer has potential, considering that it has less impact on continence and potency than radical treatment. Our systematic review indicates that despite the method being studied extensively over the past half decade, the majority of studies remain in an early research stage. The techniques high-intensity focused ultrasound and photodynamic therapy have shown most progression toward advanced research stages and show favorable results. However, more high-quality evidence is required before FT can become available as a standard treatment.

Focal therapy for primary and salvage prostate cancer treatment: a narrative review

Despite innovations in surgical technology and advancements in radiation therapy, radical treatments for clinically localized prostate cancer are associated with significant patient morbidity, including both urinary and sexual dysfunction. This has created a vital need for therapies and management strategies that provide an acceptable degree of oncologic efficacy while mitigating these undesirable side effects. Successful developments in screening approaches and advances in prostate imaging have allowed clinicians to identify, localize, and more precisely target early cancers. This has afforded urologists with an important opportunity to develop and employ focal ablation techniques that selectively destroy tumors while preserving the remainder of the gland, thus avoiding detrimental treatment effects to surrounding sensitive structures. A lack of high-level evidence supporting such an approach had previously hindered widespread adoption of focal treatments, but there are now numerous published clinical trials which have sought to establish benchmarks for safety and efficacy. As the clinical evidence supporting a potential role in prostate cancer treatment begins to accumulate, there has been a growing acceptance of focal therapy in the urologic oncology community. In this narrative review article, we describe the techniques, advantages, and side effect profiles of the most commonly utilized focal ablative techniques and analyze published clinical trial data supporting their evolving role in the prostate cancer treatment paradigm.

Current evidence for focal therapy and partial gland ablation for organ-confined prostate cancer: systematic review of literature published in the last 2 years

PURPOSE OF REVIEW

The shift in the diagnostic algorithm for prostate cancer to early imaging with mpMRI has resulted in many patients being diagnosed with small volume, apparently unilateral, clinically significant cancers. In these patients, a minimally invasive, nonmorbid intervention is appealing. The aim of this study was to review data reported within the last 2 years on focal therapy and partial gland ablation for organ-confined prostate cancer.

RECENT FINDINGS

High-intensity focal ultrasound, focal cryotherapy, photodynamic therapy, irreversible electroporation and focal laser ablation, have been used as treatment modalities for localized prostate cancer treatment. The reported oncologic outcomes vary widely and makes comparisons challenging. All the focal therapies report low rates of complications, and high rates of continence and erectile function preservation. The most common adverse events are hematuria, urinary retention and urinary tract infections. During this period, the initial results of several new technologies including MRI-guided transurethral ultrasound ablation were published.

SUMMARY

Focal therapy and partial gland ablation for organ-confined prostate cancer is an option for patients with intermediate-risk disease because of its low complication profile and preservation of QOL. Trials comparing the outcome of different focal therapy technologies have not been carried out, and the existing evidence does not point to one approach being clearly superior to others. Long-term oncologic outcome is lacking. Despite this, for men with unilateral intermediate-risk prostate cancer whose disease is often relatively indolent, focal therapy is an appealing option.

PI-RADS: what is new and how to use it

The prostate imaging reporting and data system (PI-RADS) has revolutionized the use of magnetic resonance imaging (MRI) for the management of prostate cancer (PCa). The most recent version 2.1, PI-RADS v2.1, provides specific refinements in the performance, relaxing some recommendations which were not found to be helpful, while reinforcing and clarifying others. The interpretation of T2-weighted imaging (T2WI) in the transition zone (TZ), and the overall assessment of TZ nodules, now allows for a clearer distinction between those which are clearly benign and those which might warrant tissue sampling. Additional changes also resolve discrepancies in T2WI and diffusion-weighted imaging (DWI) of the peripheral zone (PZ). PI-RADS v2.1 is a simpler, more straightforward, and more reproducible method to better communicate between physicians regarding findings on prostate MRI.