Transrectal high-intensity focused ultrasound (HIFU) treatment of localized prostate cancer: review of technical incidents and morbidity after 5 years of use

Oncological and Functional Outcomes of Whole-Gland HIFU as the Primary Treatment for Localized Prostate Cancer: A Systematic Review

INTRODUCTION

High-intensity focused ultrasound (HIFU) is regarded as a promising alternative treatment option for localized prostate cancer (PCa) as it has been proposed to offer similar oncologic control to the standard of care, but with significantly reduced treatment-related side effects. This systematic literature review assesses the available evidence of whole-gland HIFU as primary treatment for localized PCa.

METHODS

MEDLINE (PubMed) was searched for studies investigating oncological and functional outcomes following whole-gland HIFU as primary treatment for localized PCa. Our primary outcomes for the review were biochemical disease-free survival rates (BDFS), overall and PCa-specific survival rates as well as negative biopsy rates. Our secondary outcomes were functional results and complications of the treatment.

RESULTS

A total of 375 articles were identified, of which 35 were included in the present review. All 35 articles were prospective or retrospective case series. Mean/median duration of follow-up across studies was 10.9 to 94 months, and 6618 patients were included in the review. The BDFS rate varied greatly across studies from 21.7% to 89.2% during follow-up. The 10-year PCa-specific survival rate following HIFU was 90%, 99%, and 100% in 3 studies. Negative biopsy rates post-HIFU ranged from 20% to 92.7% across studies. Common side effects to HIFU included urinary incontinence (grade 1: 0%-22.7%), erectile dysfunction (11.6%-77.1%), urinary tract infections (1.5%-47.9%), and bladder outlet obstruction mainly as urethral strictures (7%-41.2%).

CONCLUSION

Great variation in oncological and functional outcomes was seen across studies. More prospective trials are needed before whole-gland HIFU can be considered as a treatment option for localized PCa.

Tissue Ablation: Applications and Perspectives

Tissue ablation techniques have emerged as a critical component of modern medical practice and biomedical research, offering versatile solutions for treating various diseases and disorders. Percutaneous ablation is minimally invasive and offers numerous advantages over traditional surgery, such as shorter recovery times, reduced hospital stays, and decreased healthcare costs. Intra-procedural imaging during ablation also allows precise visualization of the treated tissue while minimizing injury to the surrounding normal tissues, reducing the risk of complications. Here, the mechanisms of tissue ablation and innovative energy delivery systems are explored, highlighting recent advancements that have reshaped the landscape of clinical practice. Current clinical challenges related to tissue ablation are also discussed, underlining unmet clinical needs for more advanced material-based approaches to improve the delivery of energy and pharmacology-based therapeutics.

Advances in Image-Guided Ablation Therapies for Solid Tumors

Image-guided solid tumor ablation methods have significantly advanced in their capability to target primary and metastatic tumors. These techniques involve noninvasive or percutaneous insertion of applicators to induce thermal, electrochemical, or mechanical stress on malignant tissue to cause tissue destruction and apoptosis of the tumor margins. Ablation offers substantially lower risks compared to traditional methods. Benefits include shorter recovery periods, reduced bleeding, and greater preservation of organ parenchyma compared to surgical intervention. Due to the reduced morbidity and mortality, image-guided tumor ablation offers new opportunities for treatment in cancer patients who are not candidates for resection. Currently, image-guided ablation techniques are utilized for treating primary and metastatic tumors in various organs with both curative and palliative intent, including the liver, pancreas, kidneys, thyroid, parathyroid, prostate, lung, breast, bone, and soft tissue. The invention of new equipment and techniques is expanding the criteria of eligible patients for therapy, as now larger and more high-risk tumors near critical structures can be ablated. This article provides an overview of the different imaging modalities, noninvasive, and percutaneous ablation techniques available and discusses their applications and associated complications across various organs.

High-intensity focused ultrasound for prostate cancer

High-intensity focused ultrasound (HIFU) is a noninvasive procedure that has shown promising results in a wide range of malignant and nonmalignant conditions, including localized prostate cancer (PCa). This review aims to describe the application of HIFU in the management of patients with PCa, explaining its basic therapeutic principles, going through the main phases during aHIFU session, and providing an overview of the main available pieces of evidence from literature. HIFU treatment for prostate cancer is increasingly performed with high success and safety. MR guidance (MR-guided HIFU) has the advantage of real-time intraprocedural thermometric feedback that ensures that the whole region of interest has been covered by critical thermal damage (and that all surrounding healthy tissues have been spared). The absence of comparative long-term trials prevents HIFU from being considered as afirst choice for the treatment of patients with PCa.

An Introduction to High Intensity Focused Ultrasound: Systematic Review on Principles, Devices, and Clinical Applications

Ultrasound can penetrate deep into tissues and interact with human tissue via thermal and mechanical mechanisms. The ability to focus an ultrasound beam and its energy onto millimeter-size targets was a significant milestone in the development of therapeutic applications of focused ultrasound. Focused ultrasound can be used as a non-invasive thermal ablation technique for tumor treatment and is being developed as an option to standard oncologic therapies. High-intensity focused ultrasound has now been used for clinical treatment of a variety of solid malignant tumors, including those in the pancreas, liver, kidney, bone, prostate, and breast, as well as uterine fibroids and soft-tissue sarcomas. Magnetic resonance imaging and Ultrasound imaging can be combined with high intensity focused ultrasound to provide real-time imaging during ablation. Magnetic resonance guided focused ultrasound represents a novel non-invasive method of treatment that may play an important role as an alternative to open neurosurgical procedures for treatment of a number of brain disorders. This paper briefly reviews the underlying principles of HIFU and presents current applications, outcomes, and complications after treatment. Recent applications of Focused ultrasound for tumor treatment, drug delivery, vessel occlusion, histotripsy, movement disorders, and vascular, oncologic, and psychiatric applications are reviewed, along with clinical challenges and potential future clinical applications of HIFU.

Thermal Excitation of Gadolinium-Based Contrast Agents Using Spin Resonance

Theoretical and experimental investigations into the thermal excitation of liquid paramagnetic contrast agents using the spin resonance relaxation mechanism are presented. The electronic spin-lattice relaxation time τ1e of gadolinium-based contrast agents, which is estimated at 0.1 ns, is ten orders of magnitude faster than the relaxation time of protons in water. The shorter relaxation time is found to significantly increase the rate of thermal energy deposition. To the authors' knowledge this is the first study of gadolinium based contrast agents in a liquid state used as thermal agents. Analysis shows that when τ1e and other experimental parameters are optimally selected, a maximum theoretical heating rate of 29.4 °C.s-1 could be achieved which would suffice for clinical thermal ablation of neoplasms. The experimental results show a statistically significant thermal response for two out of the four contrast agents tested. The results are compared to the simulated estimates via analysis of a detailed model of the system. While these experimentally determined temperature rises are small and thus of no clinical utility, their presence supports the theoretical analysis and strongly suggests that the chemical structure of the selected compounds plays an important role in this mechanism of heat deposition. There exists an opportunity for the development of alternative gadolinium-based compounds with an order of magnitude longer τ1e in a diluted form to be used as an efficient hyperthermia agent for clinical use.

The Effects of Focal Therapy for Prostate Cancer on Sexual Function: A Combined Analysis of Three Prospective Trials

BACKGROUND

Tissue preservation by means of focal therapy offers some men with clinically significant prostate cancer an alternative to standard care that appears to confer favourable genito-urinary outcomes. The precise estimates of these outcomes have so far been based on small series.

OBJECTIVE

This analysis pools the sexual domain related patient reported outcomes from three prospective, registered studies that represent a range of inclusion criteria.

DESIGN, SETTING, AND PARTICIPANTS

One-hundred and eighteen men with localised prostate cancer (prostate specific antigen ≤ 15ng/ml, Gleason ≤ 4+3, stage ≤ T3aN0M0) treated in a tissue-preserving manner using high intensity focused ultrasound from three registered studies were included. Data on International Index of Erectile Function (IIEF-5) scores and use of phosphodiesterase-5-inhibitors were collected at baseline, and 1 mo, 3 mo, 6 mo, 9 mo, and 12 mo postoperatively. The IIEF-15 total and individual domain scores were used to assess overall sexual function. Urinary function was assessed with the International Prostate Symptom Score (IPSS), IPSS quality-of-life, and UCLA-Expanded Prostate Cancer Index Composite continence questionnaires. General health status was derived by means of the Charlson score. Multiple linear regression was used to assess whether age, grade, stage, qualitative scores (IIEF, IPSS, Expanded Prostate Cancer Index Composite, Charlson), or focal therapy type duration were associated with IIEF-5 and IIEF-15 scores at 12 mo.

RESULTS AND LIMITATIONS

Median age was 63 yr (interquartile range [IQR] 52-70 yr). Median IIEF-erectile score at baseline was 23 (IQR 11-28). This declined significantly to 9 (IQR 3-22, p<0.01) at 1 mo, but improved to 20 (IQR 9-29, p=0.30) at 1 yr posttreatment. Changes in total IIEF and other IIEF domains were only significantly different from preoperative values at 1 mo and 3 mo postoperatively. In the same period, the proportion of men using phosphodiesterase-5-inhibitors was 10% preoperatively, reaching 43% and 42% at 6 mo and 9 months before declining to 37% at 1 yr. The only baseline determinants of postoperative erectile function were total IIEF and IIEF-erectile function scores (p=0.002). The primary limitation of our study is the relatively short follow-up of 1 yr.

CONCLUSION

Men who received a range of tissue preserving therapies from the three pertinent studies experienced small decreases in total IIEF, erectile, and individual sexual domain scores that are not significantly different to those recorded at baseline. The only determinant of erectile dysfunction after tissue preserving therapy was preoperative erectile dysfunction status. Tissue preservation confers a high probability of maintaining erectile function that appears independent of all perioperative factors with the exception of baseline status.

PATIENT SUMMARY

In this report, the largest prospectively collected and published set of patients with erectile dysfunction outcomes post-focal therapy for prostate cancer, we have found a return to baseline International Index of Erectile Function-erectile and total International Index of Erectile Function scores by 6 mo post-focal therapy which was maintained at 1 yr, with the majority of patients not on any form of medical treatment for their erectile dysfunction at that point. Focal therapy may represent a suitable alternative for men of any age or comorbidity wishing to maintain erectile function.

Urethral strictures and the cancer survivor

PURPOSE OF REVIEW

Urethral stricture disease is poorly understood in prostate cancer survivors who have undergone radiation or ablative treatments. We review the cause and incidence of urethral strictures (excluding bladder neck contracture) in this setting, as well as risk factors and treatment options.

RECENT FINDINGS

Stricture rates differ for various modalities of radiation therapy, with the highest rate in high-dose-rate brachytherapy. Risk factors include higher dose of radiation delivered to prostate apex, radiation delivered per treatment, and prior transurethral resection of prostate. Cryoablation and high-intensity focused ultrasound of the prostate also carry high risk of urethral stricture formation, particularly in the salvage setting. Dilation or direct vision incision of the urethra can be utilized as a temporizing technique, with frequent recurrence. Urethral stenting is also an option; however, this is associated with a high rate of incontinence. Urethroplasty has durable outcomes for radiation-induced strictures, with a preference for excision and primary anastomosis because of the bulbomembranous location and relatively short length of these strictures. Salvage radical prostatectomy has been described in a small series as treatment for posterior urethral strictures and bladder neck contractures resulting from ablative therapies.

SUMMARY

Prostate cancer survivors treated with radiation or ablative therapies are at risk for urethral stricture formation. Urethroplasty is a feasible and durable treatment option and should be considered in the appropriate patient.

Urodynamic evaluation after high-intensity focused ultrasound for patients with prostate cancer

This prospective study assesses the impact of high-intensity focused ultrasound (HIFU) on lower urinary tract by comparing pre- and postoperative symptoms and urodynamic changes. Thirty consecutive patients with clinically organ-confined prostate cancer underwent urodynamic study before HIFU and then at 3–6 months after surgery. Continence status and symptoms were analyzed by means of International Prostate Symptoms Score IPSS and International Index Erectile Function IIEF5. As a result, there were a significant improvement in bladder outlet, maximum flow at uroflowmetry, and reduction in postvoid residual PVR at 6-month follow-up and a concomitant significant reduction of detrusor pressure at opening and at maximum flow. De novo overactive bladder and impaired bladder compliance were detected in 10% of patients at 3 months, with progressive improvement at longer follow-up. Baseline prostate volume and length of the procedure were predictors of 6-month IPSS score and continence status. In conclusion, following HIFU detrusor overactivity, decreased bladder compliance and urge incontinence represent de novo dysfunction due to prostate and bladder neck injury during surgery. However, urodynamic study shows a progressive improvement in all storage and voiding patterns at 6-month follow-up. Patients with high prostate volume and long procedure length suffered from irritative symptoms even at long term.

[Focused ultrasound therapy: current status and potential applications in neurosurgery]

High Intensity Focused Ultrasound (HIFU) therapy is an innovative approach for tissue ablation, based on high intensity focused ultrasound beams. At the focus, HIFU induces a temperature elevation and the tissue can be thermally destroyed. In fact, this approach has been tested in a number of clinical studies for the treatment of several tumors, primarily the prostate, uterine, breast, bone, liver, kidney and pancreas. For transcranial brain therapy, the skull bone is a major limitation, however, new adaptive techniques of phase correction for focusing ultrasound through the skull have recently been implemented by research systems, paving the way for HIFU therapy to become an interesting alternative to brain surgery and radiotherapy.

A Rectourethral Fistula due to Transrectal High-Intensity Focused Ultrasound Treatment: Diagnosis and Management

Colovesical fistula (CVF) is an abnormal connection between the enteric and the urinary systems. The rectourethral fistula (RUF) is a possible but extremely rare complication of treatment of prostate cancer with "transrectal High-Intensity Focused Ultrasound (HIFU) treatment." We present a case of CVF due to HIFU treatment of recurrent prostate cancer. The case was assessed with cystography completed with a pelvic CT scan-with MPR, MIP, and VR reconstruction-before emptying the bladder. Since the CT scan confirmed that the fistula involved solely the urethra and excluded even a minimal involvement of the bladder, it was possible to employ a conservative treatment by positioning a Foley catheter of monthly duration, in order to allow the urethra to rest. Still today, after 6 months, the patient is in a good clinical condition and has not shown yet signs of a recurrence of the fistula.

Clinical and future applications of high intensity focused ultrasound in cancer

High intensity focused ultrasound (HIFU) or focused ultrasound (FUS) is a promising modality to treat tumors in a complete, non invasive fashion where online image guidance and therapy control can be achieved by magnetic resonance imaging (MRI) or diagnostic ultrasound (US). In the last 10 years, the feasibility and the safety of HIFU have been tested in a growing number of clinical studies on several benign and malignant tumors of the prostate, breast, uterine, liver, kidney, pancreas, bone, and brain. For certain indications this new treatment principle is on its verge to become a serious alternative or adjunct to the standard treatment options of surgery, radiotherapy, gene therapy and chemotherapy in oncology. In addition to the now clinically available thermal ablation, in the future, focused ultrasound at much lower intensities may have the potential to become a major instrument to mediate drug and gene delivery for localized cancer treatment. We introduce the technology of MRI guided and ultrasound guided HIFU and present a critical overview of the clinical applications and results along with a discussion of future HIFU developments.

3-D photoacoustic and pulse echo imaging of prostate tumor progression in the mouse window chamber

Understanding the tumor microenvironment is critical to characterizing how cancers operate and predicting their response to treatment. We describe a novel, high-resolution coregistered photoacoustic (PA) and pulse echo (PE) ultrasound system used to image the tumor microenvironment. Compared to traditional optical systems, the platform provides complementary contrast and important depth information. Three mice are implanted with a dorsal skin flap window chamber and injected with PC-3 prostate tumor cells transfected with green fluorescent protein. The ensuing tumor invasion is mapped during three weeks or more using simultaneous PA and PE imaging at 25 MHz, combined with optical and fluorescent techniques. Pulse echo imaging provides details of tumor structure and the surrounding environment with 100-μm(3) resolution. Tumor size increases dramatically with an average volumetric growth rate of 5.35 mm(3)/day, correlating well with 2-D fluorescent imaging (R = 0.97, p < 0.01). Photoacoustic imaging is able to track the underlying vascular network and identify hemorrhaging, while PA spectroscopy helps classify blood vessels according to their optical absorption spectrum, suggesting variation in blood oxygen saturation. Photoacoustic and PE imaging are safe, translational modalities that provide enhanced depth resolution and complementary contrast to track the tumor microenvironment, evaluate new cancer therapies, and develop molecular contrast agents in vivo.