Emerging minimally invasive procedures for focal treatment of organ-confined prostate cancer

Ultrasound-mediated drug-free theranostics for treatment of prostate cancer

Lipid-shelled nanobubbles (NBs) can be visualized and activated using noninvasive ultrasound (US) stimulation, leading to significant bioeffects. Prior work demonstrates that active targeting of NBs to prostate-specific membrane antigen (PSMA) overexpressed in prostate cancer (PCa) results in enhanced cellular internalization and prolongs NB retention with persistent, cancer-cell specific acoustic activity. In this work, we hypothesized that tumor-accumulated PSMA-NBs combined with low frequency unfocused therapeutic US (TUS) will lead to selective damage and induce a specific therapeutic effect in PSMA-expressing tumors compared to PSMA-negative tumors. We observed that the internalized NBs and cellular compartments were disrupted after the PSMA-NB + TUS (targeted NB therapy or TNT) application, yet treated cells remained intact and viable. In vivo, PSMA-expressing tumors in mice receiving TNT treatment demonstrated a significantly greater extent of apoptosis (78.4 ± 9.3 %, p < 0.01) compared to controls. TNT treatment significantly inhibited the PSMA expressing tumor growth and increased median survival time by 103 %, p < 0.001). A significant reduction in tumor progression compared to untreated control was also seen in an orthotopic rabbit PCa model. Results demonstrate that cavitation of PSMA-NBs internalized via receptor-mediated endocytosis into target PCa cells using unfocused ultrasound results in significant, tumor-specific bioeffects. The effects, while not lethal to PSMA-expressing cancer cells in vitro, result in significant in vivo reduction in tumor progression in two models of PCa. While the mechanism of action of these effects is yet unclear, it is likely related to a locally-induced immune response, opening the door to future investigations in this area.

Ultrasound-mediated drug-free theranostics for treatment of prostate cancer

Rationale

Lipid-shelled nanobubbles (NBs) can be visualized and activated using noninvasive ultrasound (US) stimulation, leading to significant bioeffects. We have previously shown that active targeting of NBs to prostate-specific membrane antigen (PSMA) overexpressed in prostate cancer (PCa) enhances the cellular internalization and prolongs retention of NBs with persistent acoustic activity (~hrs.). In this work, we hypothesized that tumor-accumulated PSMA-NBs combined with low frequency therapeutic US (TUS) will lead to selective damage and induce a therapeutic effect in PSMA-expressing tumors compared to PSMA-negative tumors.

Methods

PSMA-targeted NBs were formulated by following our previously established protocol. Cellular internalization of fluorescent PSMA-NBs was evaluated by confocal imaging using late endosome/lysosome staining pre- and post-TUS application. Two animal models were used to assess the technique. Mice with dual tumors (PSMA expressing and PSMA negative) received PSMA-NB injection via the tail vein followed by TUS 1 hr. post injection (termed, targeted NB therapy or TNT). Twenty-four hours after treatment mice were euthanized and tumor cell apoptosis evaluated via TUNEL staining. Mice with single tumors (either PSMA + or -) were used for survival studies. Tumor size was measured for 80 days after four consecutive TNT treatments (every 3 days). To test the approach in a larger model, immunosuppressed rabbits with orthotopic human PSMA expressing tumors received PSMA-NB injection via the tail vein followed by TUS 30 min after injection. Tumor progression was assessed via US imaging and at the end point apoptosis was measured via TUNEL staining.

Results

In vitro TNT studies using confocal microscopy showed that the internalized NBs and cellular compartments were disrupted after the TUS application, yet treated cells remained intact and viable. In vivo, PSMA-expressing tumors in mice receiving TNT treatment demonstrated a significantly greater extent of apoptosis (78.45 ± 9.3%, p < 0.01) compared to the other groups. TNT treatment significantly inhibited the PSMA (+) tumor growth and overall survival significantly improved (median survival time increase by 103%, p < 0.001). A significant reduction in tumor progression compared to untreated control was also seen in the rabbit model in intraprostatic (90%) and in extraprostatic lesions (94%) (p = 0.069 and 0.003, respectively).

Conclusion

We demonstrate for the first time the effect of PSMA-targeted nanobubble intracellular cavitation on cancer cell viability and tumor progression in two animal models. Data demonstrate that the targeted nanobubble therapy (TNT) approach relies primarily on mechanical disruption of intracellular vesicles and the resulting bioeffects appear to be more specific to target cancer cells expressing the PSMA receptor. The effect, while not lethal in vitro, resulted in significant tumor apoptosis in vivo in both a mouse and a rabbit model of PCa. While the mechanism of action of these effects is yet unclear, it is likely related to a locally-induced immune response, opening the door to future investigations in this area.

Current Landscape of Sonodynamic Therapy for Treating Cancer

Simple Summary

Recently, ultrasound has advanced in its treatment opportunities. One example is sonodynamic therapy, a minimally invasive anti-cancer therapy involving a chemical sonosensitizer and focused ultrasound. The combination of the ultrasound and chemical sonosensitizer amplifies the drug’s ability to target cancer cells. Combining multiple chemical sonosensitizers with ultrasound can create a synergistic effect that could effectively disrupt tumorigenic growth, induce cell death, and elicit an immune response. This review provides an oversight of the application of this treatment to various types of cancer, including prostate cancer, glioma, and pancreatic ductal adenocarcinoma tumors.

Abstract

Recent advancements have tangibly changed the cancer treatment landscape. However, curative therapy for this dreadful disease remains an unmet need. Sonodynamic therapy (SDT) is a minimally invasive anti-cancer therapy involving a chemical sonosensitizer and focused ultrasound. A high-intensity focused ultrasound (HIFU) beam is used to destroy or denature targeted cancer tissues. Some SDTs are based on unfocused ultrasound (US). In some SDTs, HIFU is combined with a drug, known as a chemical sonosensitizer, to amplify the drug’s ability to damage cancer cells preferentially. The mechanism by which US interferes with cancer cell function is further amplified by applying acoustic sensitizers. Combining multiple chemical sonosensitizers with US creates a substantial synergistic effect that could effectively disrupt tumorigenic growth, induce cell death, and elicit an immune response. Therefore, the minimally invasive SDT treatment is currently attracting attention. It can be combined with targeted therapy (double-targeting cancer therapy) and immunotherapy in the future and is expected to be a boon for treating previously incurable cancers. In this paper, we will consider the current state of this therapy and discuss parts of our research.

Histotripsy: The Next Generation of High-Intensity Focused Ultrasound for Focal Prostate Cancer Therapy

This article reviews the most current methods and technological aspects of high-intensity focused ultrasound (HIFU), which is termed histotripsy. The rationale for focal therapy for prostate carcinoma rather than prostatectomy, which is being used extensively throughout Europe and Asia, is presented, and an argument for why HIFU is the modality of choice for primary therapy and recurrent disease is offered. The article presents a review of the technical advances including higher ultrasound beam energy than current thermal HIFU which allows for more accurate tissue targeting, less collateral tissue damage, and faster treatment times. Finally, the article presents a discussion about the advantage of ultrasound guidance for histotripsy in preference to magnetic resonance imaging guidance primarily based on cost, ease of application, and portability.

Moderately hypofractionated prostate external-beam radiotherapy: an emerging standard

Research over recent years has demonstrated that curative external-beam radiotherapy can be safely and efficaciously delivered with roughly half the number of treatments which was previously considered standard. We review the data supporting this change in practice, methods for implementation, as well as emerging future directions.

Effects of Focal vs Total Cryotherapy and Minimum Tumor Temperature on Patient-reported Quality of Life Compared With Active Surveillance in Patients With Prostate Cancer

OBJECTIVE

To investigate the effects of focal (hemiablation) or total cryotherapy and minimum tumor temperature on patient-reported quality of life (QoL) in patients with prostate cancer.

METHODS

An Institutional Review Board-approved database was reviewed for patients who underwent cryotherapy or active surveillance (AS). QoL questionnaire responses were collected and scores were analyzed for differences between focal and total cryotherapy and between very cold (<-76°C) and moderate-cold (≥-76°C) minimum tumor temperatures.

RESULTS

A total of 197 patients responded to a total of 547 questionnaires. Focal and total cryotherapy patients had initially lower sexual function scores relative to AS (year 1 mean difference focal: -31.7, P <.001; total: -48.1, P <.001). Focal cryotherapy was associated with a more rapid improvement in sexual function. Both focal and total cryotherapy sexual function scores were not statistically significantly different from the AS cohort by postprocedural year 4. Very cold and moderate-cold temperatures led to initially lower sexual function scores relative to AS (year 1 very cold: -38.1, P <.001; moderate-cold: -30.7, P <.001). Moderate-cold temperature scores improved more rapidly than those of very cold temperature. Neither very cold nor moderate-cold temperatures had a statistically significant difference in sexual function scores relative to AS by postprocedural year 4. Urinary function and bowel habits were not significantly different between focal and total cryotherapy and between very cold and moderate-cold temperature groups.

CONCLUSION

Focal cryotherapy and moderate-cold (≥-76°C) temperature were associated with favorable sexual function relative to total cryotherapy and very cold temperature, respectively. No significant differences in urinary function or bowel habits were observed between groups.

Patient-reported quality of life progression in men with prostate cancer following primary cryotherapy, cyberknife, or active holistic surveillance

BACKGROUND

Technological advancements have led to the success of minimally invasive treatment modalities for prostate cancer such as CyberKnife and Cryotherapy. Here, we investigate patient-reported urinary function, bowel habits, and sexual function in patients following CyberKnife (CK) or Cryotherapy treatment, and compare them with active holistic surveillance (AHS) patients.

METHODS

An IRB-approved institutional database was retrospectively reviewed for patients who underwent CK, Cryotherapy, or AHS. Quality of life (QoL) survey responses were collected every three months and the mean function scores were analyzed in yearly intervals over the 4 years post-treatment.

RESULTS

279 patients (767 survey sets) were included in the study. There was no difference among groups in urinary function scores. The CyberKnife group had significantly lower bowel habit scores in the early years following treatment (year 2 mean difference: -5.4, P < 0.01) but returned to AHS level scores by year 4. Cryotherapy patients exhibited initially lower, but not statistically significant, bowel function scores, which then improved and approached those of AHS. Both CyberKnife (year 1 mean difference: -26.7, P < 0.001) and Cryotherapy groups (-35.4, P < 0.001) had early lower sexual function scores relative to AHS, but then gradually improved and were not significantly different from AHS by the third year post-treatment. A history of hormonal therapy was associated with a lower sexual function scores relative to those patients who did not receive hormones in both CyberKnife (-18.45, P < 0.01) and Cryotherapy patients (-14.6, P < 0.05).

CONCLUSIONS

After initial lower bowel habits and sexual function scores, CyberKnife or Cryotherapy-treated patients had no significant difference in QoL relative to AHS patients. These results highlight the benefit of CyberKnife and Cryotherapy in the management of organ-confined prostate cancer.

PSA kinetics following primary focal cryotherapy (hemiablation) in organ-confined prostate cancer patients

PURPOSE

We aim to evaluate prostate-specific antigen (PSA) trends in post-primary focal cryotherapy (PFC) patients.

MATERIALS AND METHODS

This was an institutional review board-approved retrospective study of PFC patients from 2010 to 2015. Patients with at least one post-PFC PSA were included in the study. Biochemical recurrence (BCR) was determined using the Phoenix criteria. PSA bounce was also assessed. We analyzed rates of change of PSA over time of post-PFC between BCR and no BCR groups. PSA-derived variables were analyzed as potential predictors of BCR.

RESULTS

A total of 104 PFC patients were included in our analysis. Median (range) age and follow-up time were 66 (48-82) years and 19 (6.3-38.6) months, respectively. Four (3.8%) patients experienced PSA bounce. The median percent drop in first post-PFC PSA of 80.0% was not associated with BCR (p = 0.256) and may indicate elimination of the index lesion. The rate of increase of PSA in BCR patients was significantly higher compared to patients who did not recur (median PSA velocity (PSAV): 0.15 vs 0.04 ng/ml/month, p = 0.001). Similar to PSAV (HR 9.570, 95% CI 3.725-24.592, p < 0.0001), PSA nadir ≥ 2 ng/ml [HR (hazard ratio) 1.251, 95% CI 1.100-1.422, p = 0.001] was independently associated with BCR.

CONCLUSION

A significant drop in post-PFC PSA may indicate elimination of the index lesion. Patients who are likely to recur biochemically have a significantly higher PSAV compared to those who do not recur. Nadir PSA of less than 2 ng/ml may be considered the new normal PSA in focal cryotherapy (hemiablation) follow-up.

3-T multiparametric MRI characteristics of prostate cancer patients suspicious for biochemical recurrence after primary focal cryosurgery (hemiablation)

INTRODUCTION

We aimed to report on multiparametric MRI (mpMRI) characteristics of post-primary focal cryosurgery (PFC) patients suspected of biochemical recurrence (BCR) by the Phoenix criteria.

METHODS

We retrospectively reviewed all patients at our institution who had undergone PFC. Prostate-specific antigen nadir was determined using 2 or more post-PFC values. Suspicion of BCR was determined using the Phoenix criteria (nadir + 2 ng/ml). At the discretion of the physician, pre-and post-PFC 3-T mpMRIs were obtained and in a few cases biopsies were performed.

RESULTS

Ninety (58.4%) of 154 consecutive patients who underwent PFC were included in our analysis and had a median (range) age and prostate volume of 66.5 (48-82) years and 40.5 (16-175) ml, respectively. Of those suspected of BCR (37/90, 41.1%), with a median time to BCR of 19.9 (7.0-38.5) months, 27 patients (73.0%) underwent a post-PFC mpMRI. Twenty-two (81.5%) of these mpMRIs were found with 24 suspicious lesions. A considerable number (9/24, 37.5%) of these lesions were located in the central gland of the prostate. Seven of 24 lesions exhibited adverse mpMRI characteristic; 4 (16.7%) had capsular contact, 2 (8.2%) showed frank extracapsular extension, and 1 (4.2%) showed seminal vesicle invasion. Five (45.5%) of 11 patients with positive post-PFC mpMRIs were positive on biopsy (4/5, 80% were clinically significant prostate cancer).

CONCLUSION

Post-PFC mpMRI, at Phoenix suspicion of BCR, may help identify a significant number of patients failing post-PFC.

Predictors of biochemical recurrence after primary focal cryosurgery (hemiablation) for localized prostate cancer: A multi-institutional analytic comparison of Phoenix and Stuttgart criteria

BACKGROUND

The Phoenix definition (PD) and Stuttgart definition (SD) designed to determine biochemical recurrence (BCR) in patients with postradiotherapy and high-intensity focused ultrasound organ-confined prostate cancer are being applied to follow patients after cryosurgery. We sought to identify predictors of BCR using the PD and SD criteria in patients who underwent primary focal cryosurgery (PFC).

MATERIALS AND METHODS

We performed a retrospective review of patients who underwent PFC (hemiablation) at 2 referral centers from 2000 to 2014. Patients were followed up with serial prostate-specific antigen (PSA). PSA levels, pre- and post-PFC biopsy, Gleason scores, number of positive cores, and BCR (PD = [PSA nadir+2ng/ml]; SD = [PSA nadir+1.2ng/ml]) were recorded. Patients who experienced BCR were biopsied, monitored carefully or treated at the discretion of the treating urologist. Cox regression and survival analyses were performed to assess time to BCR using PD and SD.

RESULTS

A total of 163 patients were included with a median follow-up of 36.6 (interquartile range: 18.9-56.4) months. In all, 64 (39.5%) and 98 (60.5%) experienced BCR based on PD and SD, respectively. On multivariable Cox regression, the number of positive pre-PFC biopsy cores was an independent predictor of both PD (hazard ratio [HR] = 1.4, P = 0.001) and SD (HR = 1.3, P = 0.006) BCRs. Post-PFC PSA nadir was an independent predictor of BCR using the PD (HR = 2.2, P = 0.024) but not SD (HR = 1.4, P = 0.181). Survival analysis demonstrated a 3-year BCR-free survival rate of 56% and 36% for PD and SD, respectively. Of those biopsied after BCR, 14/26 (53.8%) using the PD and 18/35 (51.4%) using the SD were found to have residual/recurrent cancer. Of those with prostate cancer on post-PFC biopsy, 57.1% of those with BCR by the PD and 66.7% of those with BCR by the SD were found to have a Gleason score ≥7.

CONCLUSION

Both the PD and the SD may be used to determine BCR in post-PFC patients. However, the ideal definition of BCR after PFC remains to be elucidated.

Cryosurgery, an alternative treatment option for organ-confined prostate cancer: current beliefs and practice patterns of urologists

PURPOSE

We aim to evaluate the current beliefs and practice patterns of urologists in regard to use of cryosurgery for management of PCa.

METHODS

An anonymous 13-point survey was designed and sent out to members of the Society of Urologic Oncology (SUO), Endourological Society (ES) and American College of Cryosurgery (ACC). Descriptive statistics and univariate analyses were used to determine variables associated with the use of cryosurgery.

RESULTS

Of the 206 responses received [81 (39.2 %) SUO; 106 (51.5 %) ES; 19 (9.2 %) ACC], 83 (40.3 %) performed cryosurgery. The majority of respondents who utilize cryosurgery do so in unilateral (80.3 %) and bilateral (77.6 %) intermediate-risk PCa. Also, users of this technology indicated significant use in primary treatment (>72 %), salvage treatment (>83 %), in patients who prefer cryosurgery (89.9 %) have a life expectancy ≥10 years (65.8 %) and poor erections (74.7 %). The main reason for not utilizing cryosurgery was the lack of technical expertise (56.7 %). A urologist in a non-academic practice setting was 3.2 times more likely to perform cryosurgery compared to a urologist in an academic setting, p = 0.0001.

CONCLUSION

Cryosurgery is increasingly being accepted among urologists. However, the need for large-scale studies as well as randomized clinical trials to further delineate the benefits of cryosurgery and convince the non-users and institutions cannot be overemphasized.