Cyclophosphamide unmasks an antimetastatic effect of local tumor cryoablation

Intratumoural immunotherapy plus focal thermal ablation for localized prostate cancer

Major advances have been made in the use of immunotherapy for the treatment of solid tumours, including the use of intratumourally injected immunotherapy instead of systemically delivered immunotherapy. The success of immunotherapy in prostate cancer treatment has been limited to specific populations with advanced disease, which is thought to be a result of prostate cancer being an immunologically 'cold' cancer. Accordingly, combining intratumoural immunotherapy with other treatments that would increase the immunological heat of prostate cancer is of interest. Thermal ablation therapy is currently one of the main strategies used for the treatment of localized prostate cancer and it causes immunological activation against prostate tissue. The use of intratumoural immunotherapy as an adjunct to thermal ablation offers the potential to elicit a systemic and lasting adaptive immune response to cancer-specific antigens, leading to a synergistic effect of combination therapy. The combination of thermal ablation and immunotherapy is currently in the early stages of investigation for the treatment of multiple solid tumour types, and the potential for this combination therapy to also offer benefit to prostate cancer patients is exciting.

Hydrogel drug delivery systems for minimally invasive local immunotherapy of cancer

Although systemic immunotherapy has achieved durable responses and improved survival for certain patients and cancer types, low response rates and immune system-related systemic toxicities limit its overall impact. Intratumoral (intralesional) delivery of immunotherapy is a promising technique to combat mechanisms of tumor immune suppression within the tumor microenvironment and reduce systemic drug exposure and associated side effects. However, intratumoral injections are prone to variable tumor drug distribution and leakage into surrounding tissues, which can compromise efficacy and contribute to toxicity. Controlled release drug delivery systems such as in situ-forming hydrogels are promising vehicles for addressing these challenges by providing improved spatio-temporal control of locally administered immunotherapies with the goal of promoting systemic tumor-specific immune responses and abscopal effects. In this review we will discuss concepts, applications, and challenges in local delivery of immunotherapy using controlled release drug delivery systems with a focus on intratumorally injected hydrogel-based drug carriers.

Microwave ablation combined with anti-PD-1/CTLA-4 therapy induces an antitumor immune response to renal cell carcinoma in a murine model

The study was designed to evaluate the efficiency of microwave ablation (MWA) in combination with anti-programmed death receptor 1 (anti-PD-1)/cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) in renal cell carcinoma (RCC) treatment. After tumors were established on C57/BL6 mice, MWA treatment and/or immune checkpoint inhibitor (ICI) treatment to the mice were performed. Tumor volume was recorded every 7 days. A rechallenge test was conducted on mice with tumors in the left kidney to explore the systemic establishment of antitumor immunity on day 7. In this study, during the 21-day observation period, tumors were continued to grow in all groups. However, compared with the tumor growth rate in MWA or control group, the rate in the ICI or MWA+ICI groups was decreased. Moreover, the population of CD8+T-cells was increased only in the MWA+ICI group, while that of regulatory T cells was decreased in the MWA, ICI, and MWA+ICI groups. Additionally, the MWA+ICI group had the highest interferon-γ level among all groups. Furthermore, histopathological examination revealed that CTLA-4 expression in distant tumors was reduced in the ICI and MWA + ICI groups. MWA treatment increased PD-L1/PD-1 expression; however, after the combination treatment with ICI, PD-L1/PD-1 expression was decreased. According to the rechallenge test, mice (16.7%) in the MWA group, ICI group (50%), and MWA+ICI group (66.7%) exhibited successful tumor rejection, whereas no mice in the control group exhibited the capability of tumor rejection. Overall, the systemic antitumor immunity induced by MWA was boosted when combined with anti-PD-1/CTLA-4 treatment in an RCC murine model.

Gaseous nitric oxide tumor ablation induces an anti-tumor abscopal effect

BACKGROUND

In-situ tumor ablation provides the immune system with the appropriate antigens to induce anti-tumor immunity. Here, we present an innovative technique for generating anti-tumor immunity by delivering exogenous ultra-high concentration (> 10,000 ppm) gaseous nitric oxide (UHCgNO) intratumorally.

METHODS

The capability of UHCgNO to induce apoptosis was tested in vitro in mouse colon (CT26), breast (4T1) and Lewis lung carcinoma (LLC-1) cancer cell lines. In vivo, UHCgNO was studied by treating CT26 tumor-bearing mice in-situ and assessing the immune response using a Challenge assay.

RESULTS

Exposing CT26, 4T1 and LLC-1 cell lines to UHCgNO for 10 s-2.5 min induced cellular apoptosis 24 h after exposure. Treating CT26 tumors in-situ with UHCgNO followed by surgical resection 14 days later resulted in a significant secondary anti-tumor effect in vivo. 100% of tumor-bearing mice treated with 50,000 ppm UHCgNO and 64% of mice treated with 20,000 ppm UHCgNO rejected a second tumor inoculation, compared to 0% in the naive control for 70 days. Additionally, more dendrocytes infiltrated the tumor 14 days post UHCgNO treatment versus the nitrogen control. Moreover, T-cell penetration into the primary tumor was observed in a dose-dependent manner. Systemic increases in T- and B-cells were seen in UHCgNO-treated mice compared to nitrogen control. Furthermore, polymorphonuclear-myeloid-derived suppressor cells were downregulated in the spleen in the UHCgNO-treated groups.

CONCLUSIONS

Taken together, our data demonstrate that UHCgNO followed by the surgical removal of the primary tumor 14 days later induces a strong and potent anti-tumor response.

Targeting Tumor Acidosis and Regulatory T Cells Unmasks Anti-Metastatic Potential of Local Tumor Ablation in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is an immunologically heterogenous disease that lacks clinically actionable targets and is more likely to progress to metastatic disease than other types of breast cancer. Tumor ablation has been used to increase response rates to checkpoint inhibitors, which remain low for TNBC patients. We hypothesized that tumor ablation could produce an anti-tumor response without using checkpoint inhibitors if immunosuppression (i.e., Tregs, tumor acidosis) was subdued. Tumors were primed with sodium bicarbonate (200 mM p.o.) to reduce tumor acidosis and low-dose cyclophosphamide (100–200 mg/kg i.p.) to deplete regulatory T cells, as has been shown independently in previous studies. A novel injectable ablative was then used to necrose the tumor, release tumor antigens, and initiate an immune event that could create an abscopal effect. This combination of bicarbonate, cyclophosphamide, and ablation, called “BiCyclA”, was tested in three syngeneic models of TNBC: E0771 (C57BL/6), 67NR (BALB/c), and 4T1-Luc (BALB/c). In E0771 and 67NR, BiCyclA therapy significantly reduced tumor growth and cured 5/7 and 6/10 mice 50 days after treatment respectively. In the metastatic 4T1-Luc tumors, for which surgery and checkpoint inhibitors fail, BiCyclA cured 5/10 mice of primary tumors and lung metastases. Notably, CD4+ and CD8+ T cells were found to be crucial for the anti-metastatic response, and cured mice were able to resist tumor rechallenge, suggesting production of immune memory. Reduction of tumor acidity and regulatory T cells with ablation is a simple yet effective therapy for local and systemic tumor control with broad applicability as it is not limited by expensive supplies.

Cytoreductive prostate cryoablation and metronomic cyclophosphamide for metastatic hormone-sensitive prostate cancer

Aim: This study reports the outcomes of cytoreductive prostate cryoablation and metronomic cyclophosphamide for the treatment of metastatic hormone-sensitive prostate cancer (mHSPC). Methods: Patients with mHSPC from the authors' prostate cancer database who had received cytoreductive prostate cryoablation and metronomic cyclophosphamide were identified retrospectively. Results: Eight consecutive patients were enrolled in the study. All the patients tolerated combination therapy. The median metastatic castration-resistant prostate cancer-free survival was 62.5 months. Seven patients (87.5%) had a prostate-specific antigen nadir <0.1 ng/ml. Dysuria and hematuria before prostate cryoablation disappeared within 1 month after cryosurgery, and no incontinence was seen after prostate cryoablation. No local therapy was needed during follow-up. Conclusion: Cytoreductive prostate cryoablation and metronomic cyclophosphamide prove an effective and safe combination therapy for mHSPC.

Boosting immune response with GM-CSF optimizes primary cryotherapy outcomes in the treatment of prostate cancer: a prospective randomized clinical trial

OBJECTIVE

We explored the association of prostate cryotherapy and immunomodulation with granulocyte-macrophage colony-stimulating factor (GMCSF) in the generation of detectable tumor-specific T- and B-cell responses in men with prostate cancer.

MATERIALS AND METHODS

A randomized pilot study of patients assigned to either cryotherapy alone (Control group) or in combination with GMCSF (Treatment group). The impact of therapy on the development of T- and B-cell responses against tumor-related antigens was studied using enzyme-linked immune absorbent spot (ELISpot) and protein microarray panels (Sematrix) assays, respectively. Fold changes in response to treatment were calculated by normalization of post-treatment ELISpot values against the mean pre-cryoablation response. Student t tests between treatment and control groups at 4 weeks and 12 weeks across all the antigens were performed.

RESULTS

A total of 20 patients were randomized to either control or treatment arm. At 4 weeks after cryotherapy, the treatment group demonstrated an average fold change in cancer antigen-related antibodies of 2.8% above their mean baseline values, whereas controls averaged an 18% change below mean baseline (p < 0.05). At 12 weeks, antibody response in treatment group increased to 25% above baseline, while the average of control group patients remained 9% below baseline (p < 0.05). Patients in treatment group displayed, on average, higher ELISPOT readings for the 4- and 12-week times points (527 vs 481 for PSA and 748 vs 562 for PAP).

CONCLUSIONS

GMCSF appeared to broadly elevate antibodies against prostate-specific and nonspecific antigens. Prostate antigen-specific T-cell responses were more enhanced over non-prostate-specific responses, preferentially in the treatment group. Our findings suggest a possible therapeutic effect of adjuvant immunotherapy in association with cryotherapy for the treatment of prostate cancer.

Local Destruction of Tumors and Systemic Immune Effects

Current immune-based therapies signify a major advancement in cancer therapy; yet, they are not effective in the majority of patients. Physically based local destruction techniques have been shown to induce immunologic effects and are increasingly used in order to improve the outcome of immunotherapies. The various local destruction methods have different modes of action and there is considerable variation between the different techniques with respect to the ability and frequency to create a systemic anti-tumor immunologic effect. Since the abscopal effect is considered to be the best indicator of a relevant immunologic effect, the present review focused on the tissue changes associated with this effect in order to find determinants for a strong immunologic response, both when local destruction is used alone and combined with immunotherapy. In addition to the T cell-inflammation that was induced by all methods, the analysis indicated that it was important for an optimal outcome that the released antigens were not destroyed, tumor cell death was necrotic and tumor tissue perfusion was at least partially preserved allowing for antigen presentation, immune cell trafficking and reduction of hypoxia. Local treatment with controlled low level hyperthermia met these requisites and was especially prone to result in abscopal immune activity on its own.

Image-guided Cryotherapy for Musculoskeletal Tumors

BACKGROUND

This article represents a review of the use of image-guided cryotherapy in the treatment of musculoskeletal tumor lesions. Cryotherapy is able to induce a lethal effect on cancer cells through direct and indirect mechanisms. In this manuscript, we combined our experience with that of other authors who have published on this topic in order to provide indications on when to use cryotherapy in musculoskeletal oncology.

DISCUSSION

Image-Guided percutaneous cryotherapy is a therapeutic method now widely accepted in the treatment of patients with musculoskeletal tumors. It can be used both for palliative treatments of metastatic bone lesions and for the curative treatment of benign bone tumors, such as osteoid osteoma or osteoblastoma. In the treatment of bone metastases, cryotherapy plays a major role in alleviating or resolving disease-related pain, but it has also been demonstrated that it can have a role in local disease control. In recent years, the use of cryotherapy has also expanded for the treatment of both benign and malignant soft tissue tumors.

CONCLUSION

Percutaneous cryotherapy can be considered a safe and effective technique in the treatment of benign and malignant musculoskeletal tumors. Cryotherapy can be considered the first option in benign tumor lesions, such as osteoid osteoma, and a valid alternative to radiofrequency ablation. In the treatment of painful bone metastases, it must be considered secondarily to other standard treatments (radiotherapy, bisphosphonate therapy, and chemotherapy) when they are no longer effective in controlling the disease or when they cannot be repeated (for example, radiotherapy).

The future of cryoablation: An abscopal effect

Cryoablation has become a popular modality to treat a variety of malignant tumors in solid organs and soft tissues. In the future, the use of cryoablation should focus on its abscopal effect. The present review discusses the increased immune response triggered by cryoablation alone or by cryoablation combined with immunotherapies, which can improve the immune response and limit immunosuppression. First, cryoablative techniques should be improved to increase the area of necrosis and reduce the area of apoptosis. Second, cryoablation should be combined with immunotherapies, for example, cyclophosphamide, natural killer cells, granulocyte monocyte colony stimulating factor (GM-CSF), cytotoxic T lymphocyte-associated antigen (CTLA)-4, and programmed death receptor 1 (PD)-1 inhibitors. Cryoablation could also be combined with Hydrogen gas molecules, which were shown recently to stimulate peroxisome proliferator activated receptor gamma coactivator (PGC)-1α, thereby promoting mitochondrial function, which might rescue exhausted CD8+ T cells, leading to prolonged progression-free survival and overall survival of patients with advanced colorectal cancer.

Antitumour dendritic cell vaccination in a priming and boosting approach

Mobilizing antitumour immunity through vaccination potentially constitutes a powerful anticancer strategy but has not yet provided robust clinical benefits in large patient populations. Although major hurdles still exist, we believe that currently available strategies for vaccines that target dendritic cells or use them to present antitumour antigens could be integrated into existing clinical practice using prime-boost approaches. In the priming phase, these approaches capitalize on either standard treatment modalities to trigger in situ vaccination and release tumour antigens or vaccination with dendritic cells loaded with tumour lysates or patient-specific neoantigens. In a second boost phase, personalized synthetic vaccines specifically boost T cells that were triggered during the priming phase. This immunotherapy approach has been enabled by the substantial recent improvements in dendritic cell vaccines. In this Perspective, we discuss these improvements, highlight how the prime-boost approach can be translated into clinical practice and provide solutions for various anticipated hurdles.

Antitumor Immunity Augmented by Combining Radiofrequency Ablation with Anti-CTLA-4 Therapy in a Subcutaneous Murine Hepatoma Model

PURPOSE

To evaluate whether antitumor immunity is enhanced by combining radiofrequency (RF) ablation and anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) therapy and to evaluate its effect on untreated tumors.

MATERIALS AND METHODS

First, 40 mice with tumors established in the bilateral flanks were randomly divided into 4 groups: the control group, the RF ablation-alone group, the anti-CTLA-4-alone group, and the RF ablation + anti-CTLA-4 group. In each group, 8 mice were used for untreated tumor evaluation and survival observation, and another 2 mice were killed for histopathologic study. Then, a rechallenge test was performed in another 32 mice to determine whether systemic antitumor immunity was established.

RESULTS

Although the volume of the untreated tumors continued to increase until the end of the observation in all groups, tumor growth rates in the RF ablation + anti-CTLA-4 group were significantly smaller than tumor growth rates in the other 3 groups (all P < .05). The overall survival time of mice in the RF ablation + anti-CTLA-4 group was significantly longer than that of mice in the other 3 groups (all P < .05). Histopathologic studies of the untreated tumors showed more CD4-and CD8+ lymphocyte infiltration in mice from the RF ablation + anti-CTLA-4 group than in mice from the other 3 groups (all P < .05). After a tumor rechallenge, tumor rejection was apparent in 75% of the mice in the RF ablation + anti-CTLA-4 group, in 25% of the mice in the RF ablation group, and in 0% of the mice in the control and anti-CTLA-4 groups.

CONCLUSIONS

This study demonstrated that RF ablation-induced systemic antitumor immunity was enhanced by the combined use of anti-CTLA-4 therapy in a multi-subcutaneous murine hepatoma model.

Cytoreductive treatment strategies for de novo metastatic prostate cancer

In the past decade, a revolution in the treatment of metastatic prostate cancer has occurred with the advent of novel hormonal agents and life-prolonging chemotherapy regimens in combination with standard androgen-deprivation therapy. Notwithstanding, the use of systemic therapy alone can result in a castrate-resistant state; therefore, increasing focus is being placed on the additional survival benefits that could potentially be achieved with local cytoreductive and/or metastasis-directed therapies. Local treatment of the primary tumour with the established modalities of radiotherapy and radical prostatectomy has been explored in this context, and the use of novel minimally invasive ablative therapies has been proposed. In addition, evidence of the potential clinical benefits of metastasis-directed therapy with ionizing radiation (primarily stereotactic ablative radiotherapy) is accumulating. Herein, we summarize the pathobiological rationale for local cytoreduction and the potentially systemic immunological responses to radiotherapy and ablative therapies in patients with metastatic prostate cancer. We also discuss the current evidence base for a cytoreductive strategy, including metastasis-directed therapy, in the current era of sequential multimodal therapy incorporating novel treatments. Finally, we outline further research questions relating to this complex and evolving treatment landscape.

Immunotherapy Plus Cryotherapy: Potential Augmented Abscopal Effect for Advanced Cancers

Since the 1920s the gold standard for treating cancer has been surgery, which is typically preceded or followed with chemotherapy and/or radiation, a process that perhaps contributes to the destruction of a patient’s immune defense system. Cryosurgery ablation of a solid tumor is mechanistically similar to a vaccination where hundreds of unique antigens from a heterogeneous population of tumor cells derived from the invading cancer are released. However, releasing tumor-derived self-antigens into circulation may not be sufficient enough to overcome the checkpoint escape mechanisms some cancers have evolved to avoid immune responses. The potentiated immune response caused by blocking tumor checkpoints designed to prevent programmed cell death may be the optimal treatment method for the immune system to recognize these new circulating cryoablated self-antigens. Preclinical and clinical evidence exists for the complementary roles for Cytotoxic T-lymphocyte-associated protein (CTLA-4) and PD-1 antagonists in regulating adaptive immunity, demonstrating that combination immunotherapy followed by cryosurgery provides a more targeted immune response to distant lesions, a phenomenon known as the abscopal effect. We propose that when the host’s immune system has been “primed” with combined anti-CTLA-4 and anti-PD-1 adjuvants prior to cryosurgery, the preserved cryoablated tumor antigens will be presented and processed by the host’s immune system resulting in a robust cytotoxic CD8⁺ T-cell response. Based on recent investigations and well-described biochemical mechanisms presented herein, a polyvalent autoinoculation of many tumor-specific antigens, derived from a heterogeneous population of tumor cancer cells, would present to an unhindered yet pre-sensitized immune system yielding a superior advantage in locating, recognizing, and destroying tumor cells throughout the body.

Immuno-thermal ablations - boosting the anticancer immune response

The use of immunomodulation to treat malignancies has seen a recent explosion in interest. The therapeutic appeal of these treatments is far reaching, and many new applications continue to evolve. In particular, immune modulating drugs have the potential to enhance the systemic anticancer immune effects induced by locoregional thermal ablation. The immune responses induced by ablation monotherapy are well documented, but independently they tend to be incapable of evoking a robust antitumor response. By adding immunomodulators to traditional ablative techniques, several researchers have sought to amplify the induced immune response and trigger systemic antitumor activity. This paper summarizes the work done in animal models to investigate the immune effects induced by the combination of ablative therapy and immunomodulation. Combination therapy with radiofrequency ablation, cryoablation, and microwave ablation are all reviewed, and special attention has been paid to the addition of checkpoint blockades.

Inhibition of mouse breast adenocarcinoma growth by ablation with intratumoral alpha-irradiation combined with inhibitors of immunosuppression and CpG

It has been demonstrated that aggressive in situ tumor destruction (ablation) could lead to the release of tumor antigens, which can stimulate anti-tumor immune responses. We developed an innovative method of tumor ablation based on intratumoral alpha-irradiation, diffusing alpha-emitters radiation therapy (DaRT), which efficiently ablates local tumors and enhances anti-tumor immunity. In this study, we investigated the anti-tumor potency of a treatment strategy, which combines DaRT tumor ablation with two approaches for the enhancement of anti-tumor reactivity: (1) neutralization of immunosuppressive cells such as regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs) and (2) boost the immune response by the immunoadjuvant CpG. Mice bearing DA3 mammary adenocarcinoma with metastases were treated with DaRT wires in combination with a MDSC inhibitor (sildenafil), Treg inhibitor (cyclophosphamide at low dose), and the immunostimulant, CpG. Combination of all four therapies led to a complete rejection of primary tumors (in 3 out of 20 tumor-bearing mice) and to the elimination of lung metastases. The treatment with DaRT and Treg or MDSC inhibitors (without CpG) also resulted in a significant reduction in tumor size, reduced the lung metastatic burden, and extended survival compared to the corresponding controls. We suggest that the therapy with DaRT combined with the inhibition of immunosuppressive cells and CpG reinforced both local and systemic anti-tumor immune responses and displayed a significant anti-tumor effect in tumor-bearing mice.

Harnessing the immunomodulatory effect of thermal and non-thermal ablative therapies for cancer treatment

Minimally invasive interventional therapies are evolving rapidly and their use for the treatment of solid tumours is becoming more extensive. The in situ destruction of solid tumours by such therapies is thought to release antigens that can prime an antitumour immune response. In this review, we offer an overview of the current evidence for immune response activation associated with the utilisation of the main thermal and non-thermal ablation therapies currently in use today. This is followed by an assessment of the hypothesised mechanisms behind this immune response priming and by a discussion of potential methods of harnessing this specific response, which may subsequently be applicable in the treatment of cancer patients. References were identified through searches of PubMed/MEDLINE and Cochrane databases to identify peer-reviewed original articles, meta-analyses and reviews. Papers were searched from 1850 until October 2014. Articles were also identified through searches of the authors' files. Only papers published in English were reviewed. Thermal and non-thermal therapies have the potential to stimulate antitumour immunity although the current body of evidence is based mostly on murine trials or small-scale phase 1 human trials. The evidence for this immune-modulatory response is currently the strongest in relation to cryotherapy and radiotherapy, although data is accumulating for related ablative treatments such as high-intensity focused ultrasound, radiofrequency ablation and irreversible electroporation. This effect may be greatly enhanced by combining these therapies with other immunostimulatory interventions. Evidence is emerging into the immunomodulatory effect associated with thermal and non-thermal ablative therapies used in cancer treatment in addition to the mechanism behind this effect and how it may be harnessed for therapeutic use. A potential exists for treatment approaches that combine ablation of the primary tumour with control and possible eradication of persistent, locally recurrent and metastatic disease. However, more work is needed into each of these modalities, initially in further animal studies and then subsequently in large-scale prospective human studies.

The FORECAST study - Focal recurrent assessment and salvage treatment for radiorecurrent prostate cancer

BACKGROUND

One-third of men may experience biochemical failure by 8years following radical radiotherapy for localised prostate cancer. Over 90% of men are started on androgen deprivation therapy (ADT) which is non-curative and confers systemic side-effects. Focal salvage therapy (FST) limits collateral tissue damage and may improve therapeutic ratios. In order to deliver FST, distant disease must be ruled-out and intra-prostatic disease must be accurately detected, localised and characterised.

AIM

FORECAST - Focal Recurrent Assessment and Salvage Treatment - is a study designed to evaluate a novel imaging-based diagnostic and therapeutic complex intervention pathway for men who fail radiotherapy.

METHODS

Men with biochemical failure following radical prostate radiotherapy, prior to salvage therapy will be recruited. They will undergo whole-body multi-parametric MRI (WB-MRI), choline PET/CT, bone-scan and pelvic-mpMRI and then MRI transperineal-targeted biopsies (MRI-TB) and Transperineal Template Prostate Mapping Biopsy (TPM). Those suitable for FST will undergo either high intensity focused ultrasound (HIFU) or cryotherapy.

RESULTS

Primary outcome measures: a) the accuracy of WB-MRI to detect distant metastatic disease; b) accuracy of prostate mpMRI in local detection of radiorecurrent prostate cancer; c) detection accuracy of MRI-TB; and d) rate of urinary incontinence following FST.

CONCLUSION

Focal salvage therapy may confer lower rates of morbidity whilst retaining disease control. In order to deliver FST, intra- and extra-prostatic disease must be detected early and localised accurately. Novel diagnostic techniques including WB-MRI and MRI-TB may improve the detection of distant and local disease whilst reducing healthcare burdens compared with current imaging and biopsy strategies.

Focal cryotherapy of localized prostate cancer: a systematic review of the literature

Radical/whole gland treatment for prostate cancer has significant side-effects. Therefore focal treatments such as cryotherapy have been used to treat localized lesions whilst aiming to provide adequate cancer control with minimal side-effects. We performed a systematic review of Pubmed/Medline and Cochrane databases' to yield 9 papers for primary focal prostate cryotherapy and 2 papers for focal salvage treatment (radio-recurrent). The results of 1582 primary patients showed biochemical disease-free survival between 71-93% at 9-70 months follow-up. Incontinence rates were 0-3.6% and ED 0-42%. Recto-urethral fistula occurred in only 2 patients. Salvage focal cryotherapy had biochemical disease-free survival of 50-68% at 3 years. ED occurred in 60-71%. Focal cryotherapy appears to be an effective treatment for primary localized prostate cancer and compares favorably to radical/whole gland treatments in medium-term oncological outcomes and side-effects. Although more studies are needed it is also effective for radio-recurrent cancer with a low complications rates.

Metastatic castration-resistant prostate cancer: new therapies, novel combination strategies and implications for immunotherapy

For the past decade, docetaxel has remained the global standard of care for frontline treatment of metastatic castration-resistant prostate cancer (mCRPC). Until recently, there were limited options for patients with mCRPC following docetaxel failure or resistance, but now the approved treatment choices for these patients have expanded to include abiraterone acetate, cabazitaxel and enzalutamide. Additionally, the radioactive therapeutic agent radium-223 dichloride has been recently approved in patients with CRPC with bone metastases. Although each of these agents has been shown to convey significant survival benefit as a monotherapy, preclinical findings suggest that combining such innovative strategies with traditional treatments may achieve additive or synergistic effects, further augmenting patient benefit. This review will discuss the transformation of the post-docetaxel space in mCRPC, highlighting the spectrum of newly approved agents in this setting in the USA and the European Union, as well as summarizing treatments with non-chemotherapeutic mechanisms of action that have demonstrated promising results in recent phase 3 trials. Lastly, this review will address the potential of combinatorial regimens in mCRPC, including the pairing of novel immunotherapeutic approaches with chemotherapy, radiotherapy or androgen ablation.

Cancer immunotherapy using tumor cryoablation

Cryoablation is increasingly being used as a primary treatment for localized cancers and as a salvage therapy for metastatic cancers. Anecdotal clinical reports and animal experiments have confirmed an induction of systemic antitumor immune response by tumor cryoablation. To capitalize on the stimulatory effects of cryoablation for cancer immunotherapy, this response must be intensified using other immunomodulatory agents. This article reviews the preclinical and clinical evidence and discusses the mechanism of the antitumor immune response generated by cryoablation. The rationale and evidence behind several immunotherapy approaches that can be combined with cryoablation to devise a cryoimmunotherapeutic strategy with a potential to impact the progression of metastatic disease are described.

Cryotherapy with concurrent CpG oligonucleotide treatment controls local tumor recurrence and modulates HER2/neu immunity

Percutaneous cryoablation is a minimally invasive procedure for tumor destruction, which can potentially initiate or amplify antitumor immunity through the release of tumor-associated antigens. However, clinically efficacious immunity is lacking and regional recurrences are a limiting factor relative to surgical excision. To understand the mechanism of immune activation by cryoablation, comprehensive analyses of innate immunity and HER2/neu humoral and cellular immunity following cryoablation with or without peritumoral CpG injection were conducted using two HER2/neu(+) tumor systems in wild-type (WT), neu-tolerant, and SCID mice. Cryoablation of neu(+) TUBO tumor in BALB/c mice resulted in systemic immune priming, but not in neu-tolerant BALB NeuT mice. Cryoablation of human HER2(+) D2F2/E2 tumor enabled the functionality of tumor-induced immunity, but secondary tumors were refractory to antitumor immunity if rechallenge occurred during the resolution phase of the cryoablated tumor. A step-wise increase in local recurrence was observed in WT, neu-tolerant, and SCID mice, indicating a role of adaptive immunity in controlling residual tumor foci. Importantly, local recurrences were eliminated or greatly reduced in WT, neu tolerant, and SCID mice when CpG was incorporated in the cryoablation regimen, showing significant local control by innate immunity. For long-term protection, however, adaptive immunity was required because most SCID mice eventually succumbed to local tumor recurrence even with combined cryoablation and CpG treatment. This improved understanding of the mechanisms by which cryoablation affects innate and adaptive immunity will help guide appropriate combination of therapeutic interventions to improve treatment outcomes.

Effect of renal embolization and cryoablation on regulatory T cells in advanced renal cell carcinoma

The authors of the article "Effect of transcatheter renal arterial embolization combined with cryoablation on regulatory CD4+CD25+ T lymphocytes in the peripheral blood of patients with advanced renal carcinoma" have shown the induction of an immune response by combining renal embolization and cryoablation. This letter to the editor further analyses their findings and provides an alternative explanation for their results.

More than just tumor destruction: immunomodulation by thermal ablation of cancer

Over the past decades, thermoablative techniques for the therapy of localized tumors have gained importance in the treatment of patients not eligible for surgical resection. Anecdotal reports have described spontaneous distant tumor regression after thermal ablation, indicating a possible involvement of the immune system, hence an induction of antitumor immunity after thermoinduced therapy. In recent years, a growing body of evidence for modulation of both adaptive and innate immunity, as well as for the induction of danger signals through thermoablation, has emerged. Induced immune responses, however, are mostly weak and not sufficient for the complete eradication of established tumors or durable prevention of disease progression, and combination therapies with immunomodulating drugs are being evaluated with promising results. This article aims to summarize published findings on immune modulation through radiofrequency ablation, cryoablation, microwave ablation therapy, high-intensity focused ultrasound, and laser-induced thermotherapy.

Potent induction of tumor immunity by combining tumor cryoablation with anti-CTLA-4 therapy

Thermal ablation to destroy tumor tissue may help activate tumor-specific T cells by elevating the presentation of tumor antigens to the immune system. However, the antitumor activity of these T cells may be restrained by their expression of the inhibitory T-cell coreceptor CTLA-4, the target of the recently U.S. Food and Drug Administration-approved antibody drug ipilumimab. By relieving this restraint, CTLA-4-blocking antibodies such as ipilumimab can promote tumor rejection, but the full scope of their most suitable applications has yet to be fully determined. In this study, we offer a preclinical proof-of-concept in the TRAMP C2 mouse model of prostate cancer that CTLA-4 blockade cooperates with cryoablation of a primary tumor to prevent the outgrowth of secondary tumors seeded by challenge at a distant site. Although growth of secondary tumors was unaffected by cryoablation alone, the combination treatment was sufficient to slow growth or trigger rejection. In addition, secondary tumors were highly infiltrated by CD4(+) T cells and CD8(+) T cells, and there was a significant increase in the ratio of intratumoral T effector cells to CD4(+)FoxP3(+) T regulatory cells, compared with monotherapy. These findings documented for the first time an effect of this immunotherapeutic intervention on the intratumoral accumulation and systemic expansion of CD8(+) T cells specific for the TRAMP C2-specific antigen SPAS-1. Although cryoablation is currently used to treat a targeted tumor nodule, our results suggest that combination therapy with CTLA-4 blockade will augment antitumor immunity and rejection of tumor metastases in this setting.

Regulatory T cells are associated with post-cryoablation prognosis in patients with hepatitis B virus-related hepatocellular carcinoma

BACKGROUND

We carried out this study to evaluate the association between regulatory T cells (Treg) and prognosis and progression after cryoablation in patients with hepatitis-B virus-related hepatocellular carcinoma.

METHODS

Peripheral Treg frequency in 111 patients with hepatocellular carcinoma (HCC) was detected by flow cytometry. Treg frequency and function were re-examined during patient follow up. A possible association between Treg and α-fetoprotein (AFP) was also analyzed, and the distribution of resident CD4(+) and CD8(+) T cells and FoxP3(+) T cells in the liver tissue of patients with HCC was examined by immunohistochemistry.

RESULTS

Treg frequency significantly increased with disease progression. Our longitudinal study showed that Treg frequency had significantly decreased in 17 patients with HCC regression following cryoablation, but the frequency had dramatically increased in 14 patients with HCC recurrence or progression. Furthermore, AFP levels varied in a way comparable with Treg frequency in patients with elevated AFP recorded before therapy. Significantly increased suppressive effects of Treg on proliferation and cytokine secretion of CD8(+) and CD4(+) T cells were observed during follow up in patients with tumor progression, but not in patients with tumor response. Moreover, the numbers of CD8(+), CD4(+), and FoxP3(+) cells infiltrating the tumors around the cryotherapeutic zones were significantly decreased after argon-helium cryoablation, and this was associated with a reduction in the FoxP3/CD8 ratio. Importantly,increased quantities of circulating CD4(+)CD25(+)FoxP3(+) Treg and tumor infiltrating FoxP3(+) cells before cryoablation were associated with high recurrence or risk of progression in HCC patients after cryoablation.

CONCLUSIONS

Treg variation is associated with tumor regression or progression in HCC following cryoablation and may be used as a marker to estimate HCC progression.