Treatment of retroperitoneal sarcoma results in improved outcomes

OBJECTIVE

To report the clinical characteristics, treatments, and outcomes in a cohort of dogs with histologically confirmed retroperitoneal sarcoma (RPS) and to identify potential variables of prognostic significance.

ANIMALS

46 client-owned dogs from 10 clinics with histopathologic diagnosis of a sarcoma originating from the retroperitoneal space.

METHODS

Medical records were retrospectively reviewed to obtain information regarding clinical characteristics, treatments, and outcomes. Recorded variables were analyzed to report descriptive data for all cases and overall survival time. Multivariate analysis was utilized to evaluate prognostic factors for overall survival.

RESULTS

Hemangiosarcoma was the most common histologic subtype diagnosed (76.1%). Cytoreductive and curative intent surgical excision of the RPS was attempted in 12 and 22 dogs, respectively; 12 dogs underwent no surgery or had an exploratory laparotomy with incisional biopsy only. Nineteen dogs received adjuvant chemotherapy, either injectable or metronomic, and 1 dog received adjuvant radiation therapy. Fourteen of the 34 (41.2%) surgically treated dogs developed evidence of local recurrence, but there was no difference in local recurrence when comparing dogs categorized as curative intent versus cytoreductive surgery. The median overall survival time was 238 days. On multivariable analysis, treatment approach was associated with survival with surgical excision (vs palliative treatment) and adjuvant chemotherapy following surgery being protective against death. A diagnosis of hemangiosarcoma was associated with a greater hazard of death.

CLINICAL RELEVANCE

This study demonstrates a substantially greater survival time than previously published and suggests a survival benefit from surgical excision and adjuvant chemotherapy.

Investigating cell death responses associated with histotripsy ablation of canine osteosarcoma

BACKGROUND

Osteosarcoma (OS) is the most frequently occurring primary bone tumor in dogs and people and innovative treatment options are profoundly needed. Histotripsy is an emerging tumor ablation modality, and it is essential for the clinical translation of histotripsy to gain knowledge about the outcome of nonablated tumor cells that could remain postablation. The objective of this study was to characterize the cell death genetic signature and proliferation response of canine OS cells post a near complete histotripsy ablation (96% ± 1.5) and to evaluate genetic cell death signatures associated with histotripsy ablation and OS in vivo.

METHODS

In the current study, we ablated three canine OS cell lines with a histotripsy dose that resulted in near complete ablation to allow for a viable tumor cell population for downstream analyses. To assess the in vivo cell death genetic signature, we characterized cell death genetic signature in histotripsy-ablated canine OS tumors collected 24-h postablation.

RESULTS

Differential gene expression changes observed in the 4% viable D17 and D418 cells, and histotripsy-ablated OS tumor samples, but not in Abrams cells, were associated with immunogenic cell death (ICD). The 4% viable OS cells demonstrated significantly reduced proliferation, compared to control OS cells, in vitro.

CONCLUSION

Histotripsy ablation of OS cell lines leads to direct and potentially indirect cell death as evident by, reduced proliferation in remaining viable OS cells and cell death genetic signatures suggestive of ICD both in vitro and in vivo.

A review of the development of histotripsy for extremity tumor ablation with a canine comparative oncology model to inform human treatments

Cancer is a devasting disease resulting in millions of deaths worldwide in both humans and companion animals, including dogs. Treatment of cancer is complex and challenging and therefore often multifaceted, as in the case of osteosarcoma (OS) and soft tissue sarcoma (STS). OS predominantly involves the appendicular skeleton and STS commonly develops in the extremities, resulting in treatment challenges due to the need to balance wide-margin resections to achieve local oncological control against the functional outcomes for the patient. To achieve wide tumor resection, invasive limb salvage surgery is often required, and the patient is at risk for numerous complications which can ultimately lead to impaired limb function and mobility. The advent of tumor ablation techniques offers the exciting potential of developing noninvasive or minimally invasive treatment options for extremity tumors. One promising innovative tumor ablation technique with strong potential to serve as a noninvasive limb salvage treatment for extremity tumor patients is histotripsy. Histotripsy is a novel, noninvasive, non-thermal, and non-ionizing focused ultrasound technique which uses controlled acoustic cavitation to mechanically disintegrate tissue with high precision. In this review, we present the ongoing development of histotripsy as a non-surgical alternative for extremity tumors and highlight the value of spontaneously occurring OS and STS in the pet dog as a comparative oncology research model to advance this field of histotripsy research.

Mechanical High-Intensity Focused Ultrasound (Histotripsy) in Dogs With Spontaneously Occurring Soft Tissue Sarcomas

INTRODUCTION

Histotripsy is a non-invasive focused ultrasound therapy that uses controlled acoustic cavitation to mechanically disintegrate tissue. To date, there are no reports investigating histotripsy for the treatment of soft tissue sarcoma (STS).

OBJECTIVE

This study aimed to investigate the in vivo feasibility of ablating STS with histotripsy and to characterize the impact of partial histotripsy ablation on the acute immunologic response in canine patients with spontaneous STS.

METHODS

A custom 500 kHz histotripsy system was used to treat ten dogs with naturally occurring STS. Four to six days after histotripsy, tumors were surgically resected. Safety was determined by monitoring vital signs during treatment and post-treatment physical examinations, routine lab work, and owners' reports. Ablation was characterized using radiologic and histopathologic analyses. Systemic immunological impact was evaluated by measuring changes in cytokine concentrations, and tumor microenvironment changes were evaluated by characterizing changes in infiltration with tumor-associated macrophages (TAMs) and tumor-infiltrating lymphocytes (TILs) using multiplex immunohistochemistry and differential gene expression.

RESULTS

Results showed histotripsy ablation was achievable and well-tolerated in all ten dogs. Immunological results showed histotripsy induced pro-inflammatory changes in the tumor microenvironment. Conclusion & Significance: Overall, this study demonstrates histotripsy's potential as a precise, non-invasive treatment for STS.

High intensity focused ultrasound for the treatment of solid tumors: a pilot study in canine cancer patients

PURPOSE

To investigate the safety, feasibility, and outcomes of High-Intensity Focused Ultrasound (HIFU) for the treatment of solid tumors in a spontaneous canine cancer model.

METHODS

Dogs diagnosed with subcutaneous solid tumors were recruited, staged and pretreatment biopsies were obtained. A single HIFU treatment was delivered to result in partial tumor ablation using a commercially available HIFU unit. Tumors were resected 3-6 days post HIFU and samples obtained for histopathology and immunohistochemistry. Total RNA was isolated from paired pre and post treated FFPE tumor samples, and quantitative gene expression analysis was performed using the nCounter Canine IO Panel.

RESULTS

A total of 20 dogs diagnosed with solid tumors were recruited and treated in the study. Tumors treated included Soft Tissue Sarcoma (n = 15), Mast Cell Tumor (n = 3), Osteosarcoma (n = 1), and Thyroid Carcinoma (n = 1). HIFU was well tolerated with only 1 dog experiencing a clinically significant adverse event. Pathology confirmed the presence of complete tissue ablation at the HIFU targeted site and immunohistochemistry indicated immune cell infiltration at the treated/untreated tumor border. Quantitative gene expression analysis indicated that 28 genes associated with T-cell activation were differentially expressed post-HIFU.

CONCLUSIONS

HIFU appears to be safe and feasible for the treatment of subcutaneous canine solid tumors, resulting in ablation of the targeted tissue. HIFU induced immunostimulatory changes, highlighting the canine cancer patient as an attractive model for studying the effects of focal ablation therapies on the tumor microenvironment.

Retroperitoneal myxosarcoma in a cat

This report details a retroperitoneal myxosarcoma in a cat that exhibited extremely aggressive biological behavior. An exploratory midline celiotomy revealed a left‐sided retroperitoneal mass firmly adhered to the hypaxial musculature. Histopathological evaluation identified the mass as a myxosarcoma. Following surgical excision, the mass rapidly recurred within 6 weeks after surgery.

Cholesterol Granuloma of the Cranial Mediastinum in a Dog

A 10 yr old female spayed Pomeranian presented with a history of dyspnea and coughing and was diagnosed with a cranial mediastinal mass presumed to be a thymoma. Surgical removal was elected and occurred without intraoperative complications. Histopathology revealed the lesion to be a cholesterol granuloma. The patient developed a brief period of increased respiratory difficulty 3 days postoperatively. Thoracic radiographs showed mild pleural effusion and the patient improved with supportive care. Five months postoperatively, repeat thoracic radiographs revealed no evidence of recurrence or respiratory pathology. This case report describes a cholesterol granuloma in a unique location and reviews the pathogenesis/pathophysiology of this type of mass.

Histotripsy Ablation in Preclinical Animal Models of Cancer and Spontaneous Tumors in Veterinary Patients: A Review

New therapeutic strategies are direly needed in the fight against cancer. Over the last decade, several tumor ablation strategies have emerged as stand-alone or combination therapies. Histotripsy is the first completely noninvasive, nonthermal, and nonionizing tumor ablation method. Histotripsy can produce consistent and rapid ablations, even near critical structures. Additional benefits include real-time image guidance, high precision, and the ability to treat tumors of any predetermined size and shape. Unfortunately, the lack of clinically and physiologically relevant preclinical cancer models is often a significant limitation with all focal tumor ablation strategies. The majority of studies testing histotripsy for cancer treatment have focused on small animal models, which have been critical in moving this field forward and will continue to be essential for providing mechanistic insight. While these small animal models have notable translational value, there are significant limitations in terms of scale and anatomical relevance. To address these limitations, a diverse range of large animal models and spontaneous tumor studies in veterinary patients have emerged to complement existing rodent models. These models and veterinary patients are excellent at providing realistic avenues for developing and testing histotripsy devices and techniques designed for future use in human patients. Here, we provide a review of animal models used in preclinical histotripsy studies and compare histotripsy ablation in these models using a series of original case reports across a broad spectrum of preclinical animal models and spontaneous tumors in veterinary patients.

Histotripsy Ablation of Bone Tumors: Feasibility Study in Excised Canine Osteosarcoma Tumors

Osteosarcoma (OS) is a primary bone tumor affecting both dogs and humans. Histotripsy is a non-thermal, non-invasive focused ultrasound method using controlled acoustic cavitation to mechanically disintegrate tissue. In this study, we investigated the feasibility of treating primary OS tumors with histotripsy using a 500-kHz transducer on excised canine OS samples harvested after surgery at the Veterinary Teaching Hospital at Virginia Tech. Samples were embedded in gelatin tissue phantoms and treated with the 500-kHz histotripsy system using one- or two-cycle pulses at a pulse repetition frequency of 250 Hz and a dosage of 4000 pulses/point. Separate experiments also assessed histotripsy effects on normal canine bone and nerve using the same pulsing parameters. After treatment, histopathological evaluation of the samples was completed. To determine the feasibility of treating OS through intact skin/soft tissue, additional histotripsy experiments assessed OS with overlying tissues. Generation of bubble clouds was achieved at the focus in all tumor samples at peak negative pressures of 26.2 ± 4.5 MPa. Histopathology revealed effective cell ablation in treated areas for OS tumors, with no evidence of cell death or tissue damage in normal tissues. Treatment through tissue/skin resulted in generation of well-confined bubble clouds and ablation zones inside OS tumors. Results illustrate the feasibility of treating OS tumors with histotripsy.

Focused ultrasound tumour ablation in small animal oncology

The cancer incidence rates for humans and animals remain high, and efforts to improve cancer treatment are crucial. Cancer treatment for solid tumours includes both treatment of the primary tumour and of metastasis. Surgery is commonly employed to resect primary and metastatic tumours, but is invasive, and is not always the optimal treatment modality. Prevention and treatment of metastatic disease often utilizes a multimodal approach, but metastasis remains a major cause of death for both human and veterinary cancer patients. Focused ultrasound (FUS) tumour ablation techniques represent a novel non-invasive approach to treating cancer. FUS ablation is precise, thus sparing adjacent critical structures while ablating the tumour. FUS ablation can occur in a thermal or non-thermal fashion. Thermal FUS ablation, also known as high intensity focused ultrasound (HIFU) ablation, destroys tumour cells via heat, whereas non-thermal FUS, known as histotripsy, ablates tumour cells via mechanical disintegration of tissue. Not only can HIFU and histotripsy ablate tumours, they also demonstrate potential to upregulate the host immune system towards an anti-tumour response. The aim of this report is provide a description of HIFU and histotripsy tumour ablation, with a focus on the basic principles of their ablation mechanisms and their clinical applicability in the field of veterinary oncology.

Non-Thermal Histotripsy Ablation of Osteosarcoma Causes a Local Acute Immune Response

While surgery, chemotherapy, and radiotherapy are available as treatments for osteosarcoma, there is only a 60% 5 year overall survival rate. To address this need, novel therapies are being developed and investigated. Histotripsy is a non-invasive, non-thermal focused-ultrasound ablation therapy that uses acoustic cavitation to mechanically lyse targeted cells. Recent evidence suggests that it is immunomodulatory, and can shift the tumor microenvironment to being more pro-inflammatory. However, given histotripsy’s mechanical mechanism, it is not established to be able to treat stronger tissues such as osteosarcomas at a dose that will allow for the preservation of immune stimulating molecules. In this study, mice with subcutaneous osteosarcoma DLM8 tumors were treated with histotripsy and acute changes to the local tumor immune response were analyzed 72 hours later. Using partial ablation to avoid off-target damage, a 40% average reduction in tumor size was achieved with targeted tissues being fully ablated. Through rtPCR, the levels of various cytokines associated with wound healing were significantly increased in the treated tumors following histotripsy treatment, with the greatest fold change observed in the concentrations for IL-6 and IL-13 over a given period of time. An increase in fold change for CD274, also known as PD-L1, was also observed, implicating the potential to pair histotripsy with checkpoint inhibitors for osteosarcoma therapy. The overall results of the study suggest that histotripsy is able to shift the tumor microenvironment following partial-ablation treatment. Thus, upon activation of the immune system, wound and tissue repair mechanisms are subsequently activated and responses are regulated.

Improving Cancer Drug Discovery by Studying Cancer across the Tree of Life

Despite a considerable expenditure of time and resources and significant advances in experimental models of disease, cancer research continues to suffer from extremely low success rates in translating preclinical discoveries into clinical practice. The continued failure of cancer drug development, particularly late in the course of human testing, not only impacts patient outcomes, but also drives up the cost for those therapies that do succeed. It is clear that a paradigm shift is necessary if improvements in this process are to occur. One promising direction for increasing translational success is comparative oncology-the study of cancer across species, often involving veterinary patients that develop naturally-occurring cancers. Comparative oncology leverages the power of cross-species analyses to understand the fundamental drivers of cancer protective mechanisms, as well as factors contributing to cancer initiation and progression. Clinical trials in veterinary patients with cancer provide an opportunity to evaluate novel therapeutics in a setting that recapitulates many of the key features of human cancers, including genomic aberrations that underly tumor development, response and resistance to treatment, and the presence of comorbidities that can affect outcomes. With a concerted effort from basic scientists, human physicians and veterinarians, comparative oncology has the potential to enhance the cost-effectiveness and efficiency of pipelines for cancer drug discovery and other cancer treatments.

Lower urinary tract transitional cell carcinoma in cats: Clinical findings, treatments, and outcomes in 118 cases

Background

Lower urinary tract transitional cell carcinoma (TCC) is an important but rarely described disease of cats.

Objectives

To report the clinical characteristics, treatments, and outcomes in a cohort of cats with lower urinary tract TCC and to test identified variables for prognostic relevance.

Animals

One‐hundred eighteen client‐owned cats with lower urinary tract carcinoma.

Methods

Medical records were retrospectively reviewed to obtain information regarding clinical characteristics, treatments, and outcomes. Recorded variables were analyzed statistically.

Results

Median age of affected cats was 15 years (range, 5.0‐20.8 years) and median duration of clinical signs was 30 days (range, 0‐730 days). The trigone was the most common tumor location (32/118; 27.1%) as assessed by ultrasound examination, cystoscopy, or both. Treatment was carried out in 73 of 118 (61.9%) cats. Metastatic disease was documented in 25 of 118 (21.2%) cats. Median progression‐free survival and survival time for all cats were 113 days (95% confidence interval [CI], 69‐153) and 155 days (95% CI, 110‐222), respectively. Survival increased significantly (P < .001) when comparing cats across the ordered treatment groups: no treatment, treatment without partial cystectomy, and treatment with partial cystectomy. Partial cystectomy (hazard ratio [HR], 0.31; 95% CI, 0.17‐0.87) and treatment with nonsteroidal anti‐inflammatory drugs (HR, 0.55; 95% CI, 0.33‐0.93) were significantly associated with longer survival times.

Conclusions and Clinical Importance

The results support treatment using partial cystectomy and NSAIDs in cats with TCC.

Serial transvaginal ultrasonography following McDonald cerclage and repeat suture insertion

The aim of this study was to explore the hypothesis that serial transvaginal ultrasonography identifies early evidence of suture failure and that repeat cerclage delays delivery. We undertook a review of our policy of transvaginal ultrasonographic cervical surveillance after McDonald cerclage and of repeat suture insertion if persistent cervical effacement developed. Data from 26 pregnancies in 26 women are analyzed. The women had had a total of 57 mid-trimester miscarriages with a median of 2 (1-6) mid-trimester losses per woman. Twelve (46%) of the 26 women developed cervical changes at scan and underwent repeat cerclage. All 14 women who had a single suture inserted progressed to live births but 1 of the 13 women who had repeat cerclage had a mid-trimester miscarriage (p>0.05). The median gestation at delivery for the women who had repeat cerclage was 35 (22-39) weeks compared with 38 (36-40) weeks for those who had a single suture (p>0.05). The median interval from the detection of cervical changes at scan to delivery was 13 (4-19) weeks. Serial transvaginal ultrasonography after cervical cerclage identifies a group of women who are more likely to deliver preterm, and provides an opportunity for intervention (repeat cerclage) which appears to delay delivery by an average of 7 weeks.

INTERRELATIONSHIPS BETWEEN ASPECTS OF NITROGEN METABOLISM AND SOLUTE ACCUMULATION AND THE DISTRIBUTION OF SUBTROPICAL WOODY PLANTS IN SOUTHEAST AFRICA

Little is known of the mechanisms governing nitrogen metabolism and stress tolerance in woody plants of subtropical southeast African savannas, although many of the more widely occurring genera, particularly Acacia and Combretum species, include valuable multi-purpose trees. Basal nitrate reductase activities in vigorous leaves from 59 species and five savanna areas were used as a measure of nitrate availability. Consistently low activities were found in many of the legumes and in members of the Combretaceae. When shoots from 35 of these same species were provided with supplementary nitrate solution, increased reductase activity was recorded in a number of taxa, including non-nodulating legumes belonging to the Caesalpinioideae. Nodulating legumes did not behave in the same way. Either proline or quaternary ammonium compounds, examples of stress metabolites, accumulated in the shoots of a range of taxa belonging to a number of families. The highest concentrations occurred in shoots collected from the driest areas. Amounts of tannin were high in some species but showed no consistent pattern.