Targeted prostate cancer ablation: energy options

Real-Time and Delayed Imaging of Tissue and Effects of Prostate Tissue Ablation

PURPOSE OF REVIEW

Prostate ablation is increasingly being utilized for the management of localized prostate cancer. There are several energy modalities with varying mechanism of actions which are currently used for prostate ablation. Prostate ablations, whether focal or whole gland, are performed under ultrasound and/or MRI guidance for appropriate treatment plan execution and monitoring. A familiarity with different intraoperative imaging findings and expected tissue response to these ablative modalities is paramount. In this review, we discuss the intraoperative, early, and delayed imaging findings in prostate from the effects of prostate ablation.

RECENT FINDINGS

The monitoring of ablation both during and after the therapy became increasingly important due to the precise targeting of the target tissue. Recent findings suggest that real-time imaging techniques such as MRI or ultrasound can provide anatomical and functional information, allowing for precise ablation of the targeted tissue and increasing the effectiveness and precision of prostate cancer treatment. While intraprocedural imaging findings are variable, the follow-up imaging demonstrates similar findings across various energy modalities. MRI and ultrasound are two of the frequently used imaging techniques for intraoperative monitoring and temperature mapping of important surrounding structures. Follow-up imaging can provide valuable information about ablated tissue, including the success of the ablation, presence of residual cancer or recurrence after the ablation. It is critical and helpful to understand the imaging findings during the procedure and at different follow-up time periods to evaluate the procedure and its outcome.

Clinical application of the therapeutic ultrasound in urologic disease: Part II of the therapeutic ultrasound in urology

This article aimed to review the clinical application and evidence of the therapeutic ultrasound in detail for urological diseases such as prostate cancer, kidney tumor, erectile dysfunction, and urolithiasis. We searched for articles about high-intensity focused ultrasound (HIFU), extracorporeal shock wave therapy, ultrasound lithotripsy, and extracorporeal shockwave lithotripsy (ESWL) in the MEDLINE and Embase. HIFU may be indicated as a primary treatment for low- or intermediate-risk prostate cancer, and salvage therapy for local recurrence as a promising way to address the limitations of current standard therapies. The application of HIFU in treating kidney tumors has scarcely been reported with unsatisfactory results. Evidence indicates that low-intensity shockwave therapy improves subjective and objective erectile function in patients with erectile dysfunction. Regarding the application of ultrasound in stone management, the novel combination of ultrasound lithotripsy and other energy sources in a single probe promises to be a game-changer in efficiently disintegrating large kidney stones in percutaneous nephrolithotomy. ESWL is losing its role in managing upper urinary tract calculi worldwide. The burst-wave lithotripsy and ultrasound propulsion could be the new hope to regain its position in the lithotripsy field. According to our investigations and reviews, cavitation bubbles of the therapeutic ultrasound are actively being used in the field of urology. Although clinical evidence has been accumulated in urological diseases such as prostate cancer, kidney tumor, erectile dysfunction, and lithotripsy, further development is needed to be a game-changer in treating these diseases.

Oncologic outcome of salvage high-intensity focused ultrasound (HIFU) in radiorecurrent prostate cancer. A systematic review

INTRODUCTION

External Beam Radiation Therapy (EBRT) is one of the option available for the treatment of clinically localized prostate cancer. In patients with radiorecurrent localized prostate cancer, Androgen Deprivation Therapy (ADT) is one of the most common therapeutic strategies. However, in the last decades, other salvage treatment options have been investigated, such as brachytherapy, cryoablation and High Intensity Focused Ultrasound (Hifu).

MATERIAL AND METHODS

The oncologic outcome of Hifu in a salvage setting after EBRT failure was investigated. We reviewed the literature from 2005 to 2020 in order to report the oncologic outcome of the technique.

RESULTS

A total of 1241 patients were analyzed, with a mean age of 68.6 years and a PSA value of 5.87 ng/mL before treatment. Mean follow-up was 24.3 months after treatment, ranging from 3 to 168 months.

CONCLUSION

Our review of the literature revealed that salvage Hifu is effective in the treatment of radiorecurrent clinically localized prostate cancer, with an overall survival of 85.2% at 5 years.

Oncologic outcome, side effects and comorbidity of high-intensity focused ultrasound (HIFU) for localized prostate cancer. A review

Introduction

Prostate cancer is considered one of the most important health problems. Due to the increased number of diagnosed patients and the inability to distinguish aggressive tumors, minimally-invasive procedures have become increasingly interesting. High-intensity focused ultrasound (HIFU) is an alternative option to radical surgery to treat prostate cancer. To date, however, data on side effects and comorbidities of this technique are still not conclusive.

Methods and results

We reviewed the literature to concentrate on side effects and comorbidities of HIFU treatment of prostate cancer with the following key words: hifu, high intensity focused ultrasound, ultrasonic therapy, transrectal hifu, prostate ablation, side effects, comorbidities. MedLine and Embase via Ovid database were searched. Selection criteria were: English language, articles published between 2001 and 2015, case series including at least 100 participants and reported data on side effects and comorbidities. Sixteen uncontrolled studies were identified. No randomized controlled trials (RCT) were found in the literature comparing side effects and comorbidities of HIFU to other routine approaches to prostate cancer treatment.

Conclusion

HIFU seems to be a promising minimally-invasive treatment for low- and intermediate-risk prostate cancer, especially for patients who are unfit for radical surgery. Prospective studies with longer follow-up periods and RCT are required to properly assess the impact of side effects and comobidities related to the HIFU technique in comparison with other therapies to treat prostate cancer.

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HIFU is a promising minimally-invasive treatment for prostate cancer, especially in patients with low- and intermediate-risk disease.

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To date, the most proper indication to HIFU is for patients who are not fit for, or are unwilling to undergo, radical surgery.

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The most common complications are impotence, urinary incontinence, acute urinary retention and urethral fistula.

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High-intensity focused ultrasound is a safe and effective procedure.

Contrast-Enhanced Transrectal Ultrasound in Focal Therapy for Prostate Cancer

PURPOSE OF REVIEW

Contrast-enhanced transrectal ultrasound (CeTRUS) is an emerging imaging technique in prostate cancer (PCa) diagnosis and treatment. We review the utility and implications of CeTRUS in PCa focal therapy (FT).

RECENT FINDINGS

CeTRUS utilizes intravenous injection of ultrasound-enhancing agents followed by high-resolution ultrasound to evaluate tissue microvasculature and differentiate between benign tissue and PCa, with the latter demonstrating increased enhancement. The potential utility of CeTRUS in FT for PCa extends to pre-, intra- and post-operative settings. CeTRUS may detect PCa, facilitate targeted biopsy and aid surgical planning prior to FT. During FT, the treated area can be visualized as a well-demarcated non-enhancing zone and continuous real-time assessment allows immediate re-treatment if necessary. Following FT, the changes on CeTRUS are immediate and consistent, thus facilitating repeat imaging for comparison during follow-up. Areas suspicious for recurrence may be detected and target-biopsied. Enhancement can be quantified using time-intensity curves allowing objective assessment and comparison. Based on encouraging early outcomes, CeTRUS may become an alternative imaging modality in prostate cancer FT. Further study with larger cohorts and longer follow-up are needed.

Focal therapy for prostate cancer: concepts and future directions

PURPOSE OF REVIEW

To present a perspective on the current status and future directions of focal therapy for prostate cancer (PCa).

RECENT FINDINGS

Focal therapy for localized PCa is a rapidly evolving field. Various recent concepts - the index lesion driving prognosis, the enhanced detection of clinically significant PCa using multiparametric MRI and targeted biopsy, improved risk-stratification using novel blood/tissue biomarkers, the recognition that reducing radical treatment-related morbidity (along with reducing pathologic progression) is a clinically meaningful end-point - have all led to a growing interest in focal therapy. Novel focal therapy modalities are being investigated, mostly in phase 1 and 2 studies. Recently, level I prospective randomized data comparing partial gland ablation with a standard-of-care treatment became available from one study. Recent developments in imaging, including 7-T MRI, functional imaging, radiomics and contrast-enhanced ultrasound show early promise. We also discuss emerging concepts in patient selection for focal therapy.

SUMMARY

PCa focal therapy has evolved considerably in the recent few years. Overall, these novel focal therapy treatments demonstrate safety and feasibility, low treatment-related toxicity and acceptable short-term and in some cases medium-term oncologic outcomes. As imaging techniques evolve, patient selection, detection of clinically significant PCa and noninvasive assessment of therapeutic efficacy will be further optimized. The aspirational goal of achieving oncologic control while reducing radical treatment-related morbidity will drive further innovation in the field.

Which technology to select for primary focal treatment of prostate cancer?-European Section of Urotechnology (ESUT) position statement

BACKGROUND

With growing interest in focal therapy (FT) of prostate cancer (PCa) there is an increasing armamentarium of treatment modalities including high-intensity focused ultrasound (HIFU), cryotherapy, focal laser ablation (FLA), irreversible electroporation (IRE), vascular targeted photodynamic therapy (VTP), focal brachytherapy (FBT) and stereotactic ablative radiotherapy (SABR). Currently there are no clear recommendations as to which of these technologies are appropriate for individual patient characteristics. Our intention was to review the literature for special aspects of the different technologies that might be of advantage depending on individual patient and tumour characteristics.

METHODS

The current literature on FT was screened for the following factors: morbidity, repeatability, tumour risk category, tumour location, tumour size and prostate volume and anatomical issues. The ESUT expert panel arrived at consensus regarding a position statement on a structured pathway for available FT technologies based on a combination of the literature and expert opinion.

RESULTS

Side effects were low across different studies and FT modalities with urinary continence rates of 90-100% and erectile dysfunction between 5 and 52%. Short to medium cancer control based on post-treatment biopsies were variable between ablative modalities. Expert consensus suggested that posterior lesions are better amenable to FT using HIFU. Cryotherapy provides best possible outcomes for anterior tumours. Apical lesions, when treated with FBT, may yield the least urethral morbidity.

CONCLUSIONS

Further prospective trials are required to assess medium to long term disease control of different ablative modalities for FT. Amongst different available FT modalities our ESUT expert consensus suggests that some may be better for diffe`rent tumour locations. Tumour risk, tumour size, tumour location, and prostate volume are all important factors to consider and might aid in designing future FT trials.

"Super-active surveillance": MRI ultrasound fusion biopsy and ablation for less invasive management of prostate cancer

Multiparametric magnetic resonance imaging (mpMRI) of the prostate has allowed clinicians to better visualize and target suspicious lesions during biopsy. Targeted prostate biopsies give a more accurate representation of the true cancer volume and stage so that appropriate treatment or active surveillance can be selected. Advances in technology have led to the development of MRI and ultrasound fusion platforms used for targeted biopsies, monitoring cancer progression, and more recently for the application of focal therapy. Lesions visualized on mpMRI can be targeted for ablation with a variety of energy sources employed under both local and general anesthesia. Focal ablation may offer an alternative option for treating prostate cancer as compared to the well-established interventions of whole-gland radiation or prostatectomy. Focal ablation may also be an option for patients on active surveillance who wish to be even more "active" in their surveillance. In this review, we describe the advancements and development of fusion biopsies, the rationale behind focal therapy, and introduce focal ablative techniques for indolent prostate cancers ("super-active surveillance"), including cryoablation and focal laser ablation (FLA) and the subsequent MRI/biopsy surveillance.

Radiofrequency heat-enhanced direct intratumoral chemotherapy for prostate cancer

A novel, minimally invasive interventional technique, radiofrequency heat (RFH), has been suggested to improve the efficacy of chemotherapy for solid organ tumors. However, the treatment for prostate cancer has not been completely characterized. The aim of the present study was to investigate the in vitro and in vivo efficiency of chemotherapy in combination with RFH for the treatment of prostate cancer. The following four treatment groups were included: i) No treatment (control); ii) RFH-only; iii) chemotherapy (docetaxel)-only; and iv) combination therapy of docetaxel and RFH in human prostate cancer (HPC) cell lines and mice with HPC xenografts. In the in vitro experiments, a heating guidewire was attached under the bottom of the last chamber of the four-chamber cell culture slide, and was then connected to a radiofrequency (RF) generator. In the in vivo experiments, a tumor model was generated by subcutaneously injecting human prostate cancer cells into 24 male nu/nu mice. RFH was conducted by inserting the 0.022-inch heating-guidewire into the tumor. The follow-up magnetic resonance imaging demonstrated a significant reduction in the average tumor size in animals treated with combination therapy compared with those receiving RFH-only and chemotherapy-only. The number of apoptotic cells and the average apoptotic index of the combination therapy group were significantly higher compared with those of the other three treatment groups. In conclusion, the results of the present study suggested that RFH is able to increase the therapeutic efficiency of docetaxel in prostate cancer, and this study serves as a foundation for the future development of an interventional molecular image-guided local treatment strategy for prostate cancer that integrates RF technology, interventional oncology and direct intratumoral chemotherapy, as a replacement for systemic chemotherapy.

MRI-guided focal therapy of prostate cancer

With the advent of focal therapy as a recognized treatment option for men with prostate cancer, there are a host of emerging interventions that take advantage of MRI for image guidance. Focal therapy affords a middleground option for patients with low- to intermediate-grade prostate cancer by providing a means of keeping their cancer at bay while avoiding the negative consequences of radical therapies. However, the practice of focal treatment is far from straightforward, with some believing focal treatment errs on the side of overtreatment among patients with low-grade cancer; others worry it is undertreatment in potentially significant multifocal disease. Further research is necessary, both relating to focal therapy in general and to the utility of each MRI-guided focal treatment discussed.

Nonthermal Ablation by Using Intravascular Oxygen Radical Generation with WST11: Dynamic Tissue Effects and Implications for Focal Therapy

Purpose To examine the hypothesis that vascular-targeted photodynamic therapy (VTP) with WST11 and clinically relevant parameters can be used to ablate target tissues in a non-tumor-bearing large-animal model while selectively sparing blood vessels and collagen. Materials and Methods By using an institutional animal care and use committee-approved protocol, 68 ablations were performed in the kidneys (cortex and medulla) and livers of 27 adult pigs. Posttreatment evaluation was conducted with contrast material-enhanced computed tomography in the live animals at 24 hours. Immunohistochemistry was evaluated and histologic examination with hematoxylin-eosin staining was performed at 4 hours, 24 hours, and 7 days. Intravenous infusion of WST11 (4 mg per kilogram of body weight) was followed by using near-infrared illumination (753 nm for 20 minutes) through optical fibers prepositioned in target tissues by using a fixed template. Treated areas were scanned, measured, and statistically analyzed by using the Student t test and two-way analysis of variance. Results Focal WST11 VTP treatment in the liver and kidney by using a single optical fiber resulted in well-demarcated cylindrical zones of nonthermal necrosis concentrically oriented around the light-emitting diffuser, with no intervening viable parenchymal cells. The radius of ablated tissue increased from approximately 5 mm at 150 mW to approximately 7 mm at 415 mW (P < .01). Illumination through fiber triads at 1-cm separation resulted in confluent homogeneous necrosis. Patterns of acute injury within 24 hours were consistent with microcirculatory flow arrest and collagen preservation (demonstrated with trichrome staining). In the peripheral ablation zone, blood vessels at least 40 μm in diameter were selectively preserved and remained functional at 7 days. Ablated tissues exhibited progressive fibrosis and chronic inflammatory cell infiltrates. No histologic changes consistent with thermal injury were observed in blood vessels or collagen. The renal hilum and collecting system did not show treatment effect, despite treatment proximity. Conclusion WST11 VTP induces nonthermal tissue ablation in target tissue while preserving critical organ structures and bystander blood vessels within solid organs. (©) RSNA, 2016 Online supplemental material is available for this article.

Radiofrequency heat-enhanced chemotherapy for breast cancer: towards interventional molecular image-guided chemotherapy

Breast cancer is the most common malignancy in women worldwide. Recent developments in minimally invasive interventional radiology techniques have significantly improved breast cancer treatment. This study aimed to develop a novel technique for the local management of breast cancers using radiofrequency heat (RFH). We performed both in vitro experiments using human breast cancer cells and in vivo validation in xenograft animal models with magnetic resonance imaging (MRI) and pathological correlation to investigate the feasibility of our approach. Four treatment groups, including (1) no treatment (control), (2) RFH-only, (3) chemo (doxorubicin)-only, and (4) combination therapy with both doxorubicin and RFH, were conducted in each experiment. In vitro combination therapy significantly decreased breast cancer cell proliferation while increased their apoptosis index compared to the other three groups. MRI demonstrated a significant tumor size reduction in animals treated with combination therapy compared to those receiving other treatments in vivo. Such result was further confirmed by pathological examination. In conclusion, our findings suggests that RFH can enhance the therapeutic efficiency of doxorubicin on breast cancers, thus establishing the basis for future development of interventional molecular image-guided local chemotherapy for breast malignancies.