Rapid estimation of electroporation-dependent tissue properties in canine lung tumors using a deep neural network

The efficiency of electroporation treatments depends on the application of a critical electric field over the targeted tissue volume. Both the electric field and temperature distribution strongly depend on the tissue-specific electrical properties, which both differ between patients in healthy and malignant tissues and change in an electric field-dependent manner from the electroporation process itself. Therefore, tissue property estimations are paramount for treatment planning with electroporation therapies. Ex vivo methods to find electrical tissue properties often misrepresent the targeted tissue, especially when translating results to tumors. A voltage ramp is an in situ method that applies a series of increasing electric potentials across treatment electrodes and measures the resulting current. Here, we develop a robust deep neural network, trained on finite element model simulations, to directly predict tissue properties from a measured voltage ramp. There was minimal test error (R2>0.94;p<0.0001) in three important electric tissue properties. Further, our model was validated to correctly predict the complete dynamic conductivity curve in a previously characterized ex vivo liver model (R2>0.93;p<0.0001) within 100 s from probe insertion, showing great utility for a clinical application. Lastly, we characterize the first reported electrical tissue properties of lung tumors from five canine patients (R2>0.99;p<0.0001). We believe this platform can be incorporated prior to treatment to quickly ascertain patient-specific tissue properties required for electroporation treatment planning models or real-time treatment prediction algorithms. Further, this method can be used over traditional ex vivo methods for in situ tissue characterization with clinically relevant geometries.

Ablative and Immunostimulatory Effects of Histotripsy Ablation in a Murine Osteosarcoma Model

Background: Osteosarcoma (OS) is the most frequently occurring malignant bone tumor in humans, primarily affecting children and adolescents. Significant advancements in treatment options for OS have not occurred in the last several decades, and the prognosis remains grim with only a 70% rate of 5-year survival. The objective of this study was to investigate the focused ultrasound technique of histotripsy as a novel, noninvasive treatment option for OS. Methods: We utilized a heterotopic OS murine model to establish the feasibility of ablating OS tumors with histotripsy in a preclinical setting. We investigated the local immune response within the tumor microenvironment (TME) via immune cell phenotyping and gene expression analysis. Findings: We established the feasibility of ablating heterotopic OS tumors with ablation characterized microscopically by loss of cellular architecture in targeted regions of tumors. We observed greater populations of macrophages and dendritic cells within treated tumors and the upregulation of immune activating genes 72 h after histotripsy ablation. Interpretation: This study was the first to investigate histotripsy ablation for OS in a preclinical murine model, with results suggesting local immunomodulation within the TME. Our results support the continued investigation of histotripsy as a novel noninvasive treatment option for OS patients to improve clinical outcomes and patient prognosis.

Characterizing the Ablative Effects of Histotripsy for Osteosarcoma: In Vivo Study in Dogs

Osteosarcoma (OS) is a malignant bone tumor treated by limb amputation or limb salvage surgeries and chemotherapy. Histotripsy is a non-thermal, non-invasive focused ultrasound therapy using controlled acoustic cavitation to mechanically disintegrate tissue. Recent ex vivo and in vivo pilot studies have demonstrated the ability of histotripsy for ablating OS but were limited in scope. This study expands on these initial findings to more fully characterize the effects of histotripsy for bone tumors, particularly in tumors with different compositions. A prototype 500 kHz histotripsy system was used to treat ten dogs with suspected OS at an intermediate treatment dose of 1000 pulses per location. One day after histotripsy, treated tumors were resected via limb amputation, and radiologic and histopathologic analyses were conducted to determine the effects of histotripsy for each patient. The results of this study demonstrated that histotripsy ablation is safe and feasible in canine patients with spontaneous OS, while offering new insights into the characteristics of the achieved ablation zone. More extensive tissue destruction was observed after histotripsy compared to that in previous reports, and radiographic changes in tumor size and contrast uptake following histotripsy were reported for the first time. Overall, this study significantly expands our understanding of histotripsy bone tumor ablation and informs future studies for this application.

Histotripsy Ablation of Spontaneously Occurring Canine Bone Tumors In Vivo

OBJECTIVE

Osteosarcoma (OS) is a devastating primary bone tumor in dogs and humans with limited non-surgical treatment options. As the first completely non-invasive and non-thermal ablation technique, histotripsy has the potential to significantly improve the standard of care for patients with primary bone tumors.

INTRODUCTION

Standard of care treatment for primary appendicular OS involves surgical resection via either limb amputation or limb-salvage surgery for suitable candidates. Biological similarities between canine and human OS make the dog an informative comparative oncology research model to advance treatment options for primary OS. Evaluating histotripsy for ablating spontaneous canine primary OS will build a foundation upon which histotripsy can be translated clinically into a standard of care therapy for canine and human OS.

METHODS

Five dogs with suspected spontaneous OS were treated with a 500 kHz histotripsy system guided by real-time ultrasound image guidance. Spherical ablation volumes within each tumor (1.25-3 cm in diameter) were treated with single cycle histotripsy pulses applied at a pulse repetition frequency of 500 Hz and a dose of 500 pulses/point.

RESULTS

Tumor ablation was successfully identified grossly and histologically within the targeted treatment regions of all subjects. Histotripsy treatments were well-tolerated amongst all patients with no significant clinical adverse effects. Conclusion & Significance: Histotripsy safely and effectively ablated the targeted treatment volumes in all subjects, demonstrating its potential to serve as a non-invasive treatment modality for primary bone tumors.

Distribution of histopathologic types of primary pulmonary neoplasia in dogs and outcome of affected dogs: 340 cases (2010-2019)

OBJECTIVE

To provide updated information on the distribution of histopathologic types of primary pulmonary neoplasia in dogs and evaluate the effect of postoperative adjuvant chemotherapy in dogs with pulmonary carcinoma.

ANIMALS

340 dogs.

PROCEDURES

Medical records of dogs that underwent lung lobectomy for removal of a primary pulmonary mass were reviewed, and histopathologic type of lesions was determined. The canine lung carcinoma stage classification system was used to determine clinical stage for dogs with pulmonary carcinoma.

RESULTS

Pulmonary carcinoma was the most frequently encountered tumor type (296/340 [87.1%]), followed by sarcoma (26 [7.6%]), adenoma (11 [3.2%]), and pulmonary neuroendocrine tumor (5 [1.5%]); there was also 1 plasmacytoma and 1 carcinosarcoma. Twenty (5.9%) sarcomas were classified as primary pulmonary histiocytic sarcoma. There was a significant difference in median survival time between dogs with pulmonary carcinomas (399 days), dogs with histiocytic sarcomas (300 days), and dogs with neuroendocrine tumors (498 days). When dogs with pulmonary carcinomas were grouped on the basis of clinical stage, there were no significant differences in median survival time between dogs that did and did not receive adjuvant chemotherapy.

CLINICAL RELEVANCE

Results indicated that pulmonary carcinoma is the most common cause of primary pulmonary neoplasia in dogs; however, nonepithelial tumors can occur. Survival times were significantly different between dogs with pulmonary carcinoma, histiocytic sarcoma, and neuroendocrine tumor, emphasizing the importance of recognizing the relative incidence of these various histologic diagnoses. The therapeutic effect of adjuvant chemotherapy in dogs with pulmonary carcinoma remains unclear and warrants further investigation.

Local Administration of Carboplatin in Poloxamer 407 After an Ulnar Osteosarcoma Removal in a Dog

An 8 yr old male castrated hound presented for a left distal ulnar osteosarcoma. Staging (computed tomography and nuclear scintigraphy) did not reveal any metastases. A limb-sparing ulnectomy with local adjunctive carboplatin in a poloxamer copolymer gel (poloxamer 407) was performed. The patient recovered without complications after surgery. No wound healing complications or adverse effects occurred after local use of carboplatin in poloxamer 407. The local recurrence-free interval was 296 days from surgery, and the survival time was 445 days from initial diagnosis. This is the first report in the veterinary literature of using poloxamer 407 as a carrier for local delivery of chemotherapeutic drugs in a clinical patient.

Outcome and postoperative complications in 73 dogs with thyroid carcinoma with gross vascular invasion managed with thyroidectomy

Excellent outcomes have been reported following thyroidectomy for thyroid carcinoma in dogs, but outcomes for thyroid carcinomas with gross vascular invasion are poorly described. This study describes the clinical outcomes and complications in dogs with thyroid carcinomas with gross vascular invasion undergoing thyroidectomy. Medical records of dogs that underwent thyroidectomy between January 1st 2010 and December 31st 2019 were reviewed at 10 hospitals. Signalment, diagnostic data, primary and adjuvant treatments performed, and outcome were abstracted. Survival was calculated using Kaplan-Meier analysis. Multiple logistic regression was used to identify variables associated with disease-specific survival. Seventy-three dogs were included, of which 58 underwent unilateral thyroidectomy and 15 underwent bilateral thyroidectomy. Complications were reported in five dogs (three major, two minor; 6.8%) intraoperatively and 12 dogs (two major leading to death, 10 minor; 16.4%) postoperatively. Seven (9.6%) dogs developed locoregional recurrence at a median of 238 days postoperatively (range: 15-730 days). Distant metastasis was suspected or confirmed in nine dogs (12.3%) at a median of 375 days postoperatively (range: 50-890 days). Twenty-seven dogs (37%) received adjuvant therapy (chemotherapy: n = 21; radiotherapy: n = 6). Thirty-nine dogs were euthanized or died, with 20 deaths related to disease (n = 10) or of unknown cause (n = 10), 19 due to unrelated causes, and nine lost to follow-up. Median overall and disease-specific survival were 621 days and not reached respectively. One-year disease-specific survival rate was 82.5%. No variables were associated with disease-specific survival in our dataset. Surgery may be considered for loco-regional therapy in dogs with thyroid carcinoma with gross vascular invasion.

Evaluation of Myogenin and MyoD1 as Immunohistochemical Markers of Canine Rhabdomyosarcoma

Canine rhabdomyosarcoma (RMS) presents a diagnostic challenge due to its overlapping histologic features with other soft tissue sarcomas. The diagnosis of RMS currently relies on positive immunohistochemical (IHC) labeling for desmin; however, desmin expression is also observed in non-RMS tumors. Myogenin and MyoD1 are transcription factors reported to be sensitive and specific IHC markers for human RMS, but they are not widely used in veterinary oncology. The goals of this study were to develop an IHC protocol for myogenin and MyoD1, evaluate myogenin and MyoD1 labeling in canine RMS, and report clinical outcomes. Sixteen cases of possible RMS were retrospectively evaluated. A diagnosis of RMS was confirmed in 13 cases based on histological features and immunolabeling for myogenin and MyoD1, with the aid of electron microscopy in 2 cases. Desmin was negative in 3 cases of RMS. Two cases were of the sclerosing variant. The median age of dogs with RMS was 7.2 years. Anatomic tumor locations included previously reported sites such as bladder, larynx, heart, and orbit, as well as other locations typical of soft tissue sarcomas. Survival ranged from 47 to 1480 days for 5 dogs with available data. This study demonstrated that MyoD1 and myogenin should be included with desmin as part of a diagnostic IHC panel for canine RMS. Utilization of these antibodies to improve the accuracy of canine RMS diagnosis will ultimately allow for better characterization of the biological behavior and clinical outcomes of this disease, providing the groundwork for future comparative investigations in canine RMS.

Clinical outcomes in dogs with localized splenic histiocytic sarcoma treated with splenectomy with or without adjuvant chemotherapy

Background

Localized splenic histiocytic sarcoma (HS) in dogs is a poorly understood disease, and could have longer survival times than disseminated or hemophagocytic HS. Understanding the clinical behavior of localized splenic HS can refine treatment recommendations.

Objective

To describe the clinical characteristics and outcomes of dogs with localized splenic HS.

Animals

Fourteen client‐owned dogs with histologically confirmed splenic HS that received splenectomy.

Methods

Multi‐institutional retrospective case series—medical records of dogs with splenic HS were reviewed. Dog signalment, clinicopathologic data, primary and adjuvant treatments, and outcomes were obtained. Survival data were calculated using Kaplan‐Meier analysis. Dog variables such as age, weight, platelet counts were reported using descriptive statistics. The Cox proportional hazards regression method was used to determine whether potential risk factors (weight, age, albumin level, hematocrit, and platelet count) were associated with PFI.

Results

Median survival time for the dogs in this study was 427 days. Twelve dogs received adjuvant lomustine‐based chemotherapy. Five dogs (35.7%) were suspected or confirmed to have developed metastatic disease. Eleven dogs died of disease, 1 dog died of unrelated cause, and 2 dogs were alive at final follow‐up.

Conclusions and Clinical Significance

Histiocytic sarcoma in dogs can manifest as a localized form in the spleen. Dogs with localized splenic HS treated with surgery ± chemotherapy can experience survival times over a year.

Histologically low-grade, yet biologically high-grade, canine cutaneous mast cell tumours: A systematic review and meta-analysis of individual participant data

Low-grade canine cutaneous mast cell tumour (cMCT) with metastasis at the time of treatment is uncommonly reported, with few studies focusing on this specific clinical entity. The specific objective of this study was to systematically review the veterinary literature and perform a meta-analysis summarizing the clinical presentation, treatments reported and clinical outcomes from dogs with histologically low-grade cMCT and metastasis present at initial treatment. A total of 980 studies were screened with eight publications providing data on 121 dogs ultimately included. The most common treatments were surgery with adjuvant chemotherapy in 83/121 (69%) dogs; combined surgery, radiation and chemotherapy in 17/121 (14%) dogs; chemotherapy alone in 12/121 (10%) dogs and surgery alone in 7/121 (6%) dogs. Dogs with distant metastasis (n = 22) experienced significantly shorter survival compared with those with regional lymph node (RLN) metastasis (n = 99; median 194 vs 637 days; P < .01). Two variables were significantly associated with increased risk of death: presence of distant (vs RLN) metastasis (hazard ratio = 2.60; P < .01) and not receiving surgery as a component of treatment (hazard ratio = 3.79; P < .01). Risk of bias was judged to be low in terms of selection and performance bias but high in terms of detection and exclusion bias. In conclusion, dogs with cMCT and RLN metastasis can be expected to live significantly longer than those with distant metastasis, and surgery appears to have a role in extending survival of metastatic low-grade cMCT.

Immune dysregulation and osteosarcoma: Staphylococcus aureus downregulates TGF-β and heightens the inflammatory signature in human and canine macrophages suppressed by osteosarcoma

Since William Coley utilized bacterial immunotherapy to treat sarcomas in the late 19th century, an association between infection and improved survival has been reported for human and canine osteosarcoma patients. One of the reasons for this improved survival is likely a reactivation of the host immune system towards an inflammatory anti-tumour response, and one of the key players is the macrophage. Yet, despite their importance, the response of macrophages to infectious agents in the context of osteosarcoma has not been thoroughly evaluated. The aim of this study was to evaluate how in vitro exposure to a bacterial agent (Staphylococcus aureus) influenced canine and human macrophage differentiation in the presence of osteosarcoma. Our hypothesis was that S. aureus would, in the presence of osteosarcoma, induce a macrophage phenotype with significantly increased inflammatory signatures. Consistent with our hypothesis, human macrophages co-cultured with osteosarcoma and S. aureus exhibited increased IFN-γ, TNF-α and IL-12p70 cytokine secretion, decreased TGF-β cytokine secretion and increased mRNA expression of TNF-α when compared with macrophages co-cultured with osteosarcoma and to macrophages cultured alone. Canine macrophages similarly exhibited increased IFN-γ and TNF-α cytokine secretion, decreased TGF-β cytokine secretion, increased mRNA expression of TNF-α and increased surface receptor expression of CD80 when co-cultured with osteosarcoma and S. aureus. Collectively, the findings of this study suggest that infection upregulates the inflammatory immune response to counteract osteosarcoma-induced immune suppression. This work informs a potential therapeutic strategy to optimize inflammatory stimuli for triggering an anti-osteosarcoma macrophage response.

Bilateral caudal maxillectomy for resection of tumors crossing palatal midline and use of the angularis oris axial pattern flap for primary closure or dehiscence repair in two dogs

OBJECTIVE

To describe the technique and outcomes for bilateral caudal maxillectomy for resection of large caudal maxillary tumors crossing palatal midline in two dogs.

STUDY DESIGN

Clinical case report.

ANIMALS

Two client-owned dogs.

METHODS

Two client-owned dogs with primary caudal maxillary tumors, a poorly differentiated sarcoma, and a multilobulated osteochondrosarcoma. Bilateral caudal maxillectomies were performed for curative-intent resection of these tumors. The angularis oris axial pattern flap was used for primary closure in one dog and for dehiscence repair in the other.

RESULTS

Both tumors were resected with complete histologic margins. The defects were closed with local buccal mucosal flaps, with or without a unilateral angularis oris flap. Esophagostomy tubes were placed at time of surgery to bypass oral feeding. Incisional dehiscence and subsequent oronasal fistula formation occurred as a postoperative complication in both dogs (3 and 10 days, respectively). Both were successfully repaired with a combination of local buccal mucosal flaps and the angularis oris flap. Both dogs had good functional outcome and quality of life after recovery from revision surgery.

CONCLUSION

Bilateral caudal maxillectomy allowed resection of caudal maxillary tumors crossing palatal midline, with good function and quality of life after recovery in 2 dogs.

CLINICAL SIGNIFICANCE

Good outcomes including complete resections are achievable with bilateral caudal maxillectomy despite complications. Local mucosal and axial pattern flaps can be used for dehiscence repair.

Influence of surgical margin completeness on risk of local tumour recurrence in canine cutaneous and subcutaneous soft tissue sarcoma: A systematic review and meta-analysis

The present peer-reviewed veterinary literature contains conflicting information regarding the impact of surgical margin completeness on risk of local tumour recurrence in canine soft tissue sarcoma (STS). This systematic review and meta-analysis was designed to answer the clinical question: "Does obtaining microscopically tumour-free surgical margins reduce risk for local tumour recurrence in canine cutaneous and subcutaneous STS?" A total of 486 citations were screened, 66 of which underwent full-text evaluation, with 10 studies representing 278 STS excisions ultimately included. Cumulatively, 16/164 (9.8%) of completely excised and 38/114 (33.3%) of incompletely excised STS recurred. Overall relative risk of 0.396 (95% confidence interval = 0.248-0.632) was calculated for local recurrence in STS excised with complete margins as compared to STS excised with incomplete margins. Risk of bias was judged to be low for all studies in terms of selection bias and detection bias but high for all studies in terms of performance bias and exclusion bias. The results of the present meta-analysis, coupled with the results of individual previous studies, strongly suggest that microscopically complete surgical margins confer a significantly reduced risk for local tumour recurrence in canine STS. Future studies ideally should adhere to standardized conducting and reporting guidelines to reduce systematic bias.

Long-term outcomes of dogs undergoing surgical resection of mast cell tumors and soft tissue sarcomas: A prospective 2-year-long study

OBJECTIVE

Report clinical outcomes of dogs with surgically excised mast cell tumors (MCT) and soft tissue sarcomas (STS).

STUDY DESIGN

Prospective clinical study.

SAMPLE POPULATION

Fifty-three dogs with 52 MCT (50 low grade, 2 high grade) and 19 STS (12 grade I, 6 grade II, 1 grade III).

METHODS

All dogs were examined at 3, 6, 12, 18, and 24 months postoperatively, with cytologic or histopathologic evaluation of suspected local recurrences. Dogs euthanized because of study tumor-related causes underwent necropsy.

RESULTS

Median intraoperative margins were 20 mm and 30 mm wide for MCT and STS, respectively, with 1 fascial plane resected en bloc. The narrowest histologic tumor-free margins measured <1 mm in 21 of 52 (40%) MCT and 7 of 19 (37%) STS. All dogs were followed for 24 months. Two of 50 (4%) low-grade MCT were diagnosed, with local recurrence 181 and 265 days postoperatively. Two of 36 (6%) dogs with low-grade MCT developed visceral metastasis 181 and 730 days postoperatively. One of 2 dogs with high-grade MCT developed local recurrence 115 days postoperatively. No local recurrence or metastasis was diagnosed after excision of 19 STS.

CONCLUSION

Local recurrence rates among predominantly low- to intermediate-grade MCT and STS were low, despite a high prevalence of histologic tumor-free margins <1 mm. Surgical recommendations for high-grade tumors cannot be extrapolated from this population.

CLINICAL SIGNIFICANCE

Surgeons should seek to achieve microscopically complete excision for MCT and STS while minimizing patient morbidity and considering limitations of histopathology in predicting outcomes.

Assessment of a novel nanoparticle hyperthermia therapy in a murine model of osteosarcoma

OBJECTIVE

To evaluate the effects of nanoparticle hyperthermia therapy on monocyte function and tumor-derived factors associated with macrophage polarization in a murine osteosarcoma model.

STUDY DESIGN

Experimental study.

ANIMALS

Female C3H mice.

METHODS

Peripheral blood monocyte cell surface phenotype, monocyte chemotaxis, tumor messenger RNA expression, and survival were compared among osteosarcoma (OS)-bearing mice treated with nanoparticle hyperthermia therapy, OS-bearing mice with osteomyelitis, OS-bearing mice, vehicle control mice, and normal control mice.

RESULTS

OS-bearing mice with osteomyelitis had a higher proportion of "nonclassical" monocytes (Ly6C^lo ) compared with all other experimental groups. There were alterations in monocyte expression of multiple chemokine receptors among experimental groups including CXCR2, CCR2, and CXCR4. Monocytes from OS-bearing mice treated with hyperthermia therapy exhibited greater chemotaxis compared with monocytes from OS-bearing mice with osteomyelitis.

CONCLUSION

OS likely induced alterations in monocyte phenotype and function. Nanoparticle hyperthermia therapy increased in vitro monocyte chemotaxis.

CLINICAL IMPACT

Enhancing monocyte/macrophage function in dogs with OS may enhance antitumor immunity.

T Regulatory Cell Induced Foxp3 Binds the IL2, IFNγ, and TNFα Promoters in Virus-Specific CD8+ T Cells from Feline Immunodeficiency Virus Infected Cats

Polyfunctional CD8⁺ T cells play a critical role in controlling viremia during AIDS lentiviral infections. However, for most HIV-infected individuals, virus-specific CD8⁺ T cells exhibit loss of polyfunctionality, including loss of IL2, TNFα, and IFNγ. Using the feline immunodeficiency virus (FIV) model for AIDS lentiviral persistence, our laboratory has demonstrated that FIV-activated Treg cells target CD8⁺ T cells, leading to a reduction in IL2 and IFNγ production. Furthermore, we have demonstrated that Treg cells induce expression of the repressive transcription factor, Foxp3, in CD8⁺ T cells. Based upon these findings, we asked if Treg-induced Foxp3 could bind to the IL2, TNFα, and IFNγ promoter regions in virus-specific CD8⁺ T cells. Following coculture with autologous Treg cells, we demonstrated decreased mRNA levels of IL2 and IFNγ at weeks 4 and 8 postinfection and decreased TNFα at week 4 postinfection in virus-specific CD8⁺ T cells. We also clearly demonstrated Treg cell-induced Foxp3 expression in virus-specific CD8⁺ T cells at weeks 1, 4, and 8 postinfection. Finally, we documented Foxp3 binding to the IL2, TNFα, and IFNγ promoters at 8 weeks and 6 months postinfection in virus-specific CD8⁺ T cells following Treg cell coculture. In summary, the results here clearly demonstrate that Foxp3 inhibits IL2, TNFα, and IFNγ transcription by binding to their promoter regions in lentivirus-specific CD8⁺ T cells. We believe this is the first description of this process during the course of AIDS lentiviral infection.

Micro-RNA 10a Is Increased in Feline T Regulatory Cells and Increases Foxp3 Protein Expression Following In Vitro Transfection

CD4⁺CD25⁺Foxp3⁺ T regulatory (Treg) cells are activated during the course of lentiviral infection and exhibit heightened suppressor function when compared to Treg cells from uninfected controls. Foxp3 is essential to Treg cell function and multiple studies have documented that lentivirus-activated Treg cells exhibit heightened Foxp3 expression when compared to Treg cells from uninfected controls. Our hypothesis was that lentivirus-induced micro-RNAs (miRNAs) contribute to heightened Treg cell suppressor function by stabilizing Foxp3 expression. We demonstrated that CD4⁺CD25⁺ T cells from both feline immunodeficiency virus infected (FIV⁺) cats and uninfected control cats exhibit increased miRNA 10a and 21 levels compared to autologous CD4⁺CD25⁻ T cells but there was no difference in the levels of these miRNAs when Treg cells from FIV⁺ cats were compared to Treg cells from uninfected controls. Further, there was no increase in Foxp3 mRNA following transfection of miRNA 10a or 21 into a feline cell line. However, transfection with miRNA 10a resulted in increased Foxp3 protein expression.

Association of Canine Osteosarcoma and Monocyte Phenotype and Chemotactic Function

Background

Monocytes/macrophages are likely key cells in immune modulation in dogs with osteosarcoma (OSA). Increased peripheral monocyte counts are negatively correlated with shorter disease‐free intervals in dogs with OSA. Understanding the monocyte/macrophage's modulatory role in dogs with OSA can direct further studies in immunotherapy development for OSA.

Hypothesis/Objectives

That OSA evades the immune response by down‐regulating monocyte chemokine receptor expression and migratory function, and suppresses host immune responses.

Animals

Eighteen dogs with OSA that have not received definitive treatment and 14 healthy age‐matched controls

Methods

Clinical study—expression of peripheral blood monocyte cell surface receptors, monocyte mRNA expression and cytokine secretion, monocyte chemotaxis, and survival were compared between clinical dogs with OSA and healthy control dogs.

Results

Cell surface expression of multiple chemokine receptors is significantly down‐regulated in peripheral blood monocytes of dogs with OSA. The percentage expression of CCR2 (median 58%, range 2–94%) and CXCR2 expression (median 54%, range 2–92%) was higher in control dogs compared to dogs with OSA (CCR2 median 29%, range 3–45%, P = 0.0006; CXCR2 median 23%, range 0.2–52%, P = 0.0007). Prostaglandin E₂ (PGE₂) (OSA, median 347.36 pg/mL, range 103.4–1268.5; control, 136.23 pg/mL, range 69.93–542.6, P = .04) and tumor necrosis factor‐alpha (TNF‐α) (P = .02) levels are increased in OSA monocyte culture supernatants compared to controls. Peripheral blood monocytes of dogs with OSA exhibit decreased chemotactic function when compared to control dogs (OSA, median 1.2 directed to random migration, range 0.8–1.25; control, 1.6, range of 0.9–1.8, P = .018).

Conclusions and Clinical Importance

Dogs with OSA have decreased monocyte chemokine receptor expression and monocyte chemotaxis, potential mechanisms by which OSA might evade the immune response. Reversal of monocyte dysfunction using immunotherapy could improve survival in dogs with OSA.

Durations of bone consolidation and external fixation after distraction osteogenesis in dogs

OBJECTIVE

To evaluate the influence of epidemiologic, surgical, and mechanical factors on the durations of bone consolidation and external fixation after distraction osteogenesis in dogs.

STUDY DESIGN

Retrospective cohort study.

SAMPLE POPULATION

Dogs (n = 115) that had corrective osteotomy with circular external fixation (CEF; n = 152) METHODS: Medical and radiographic records (1992-2012) of dogs that had corrective osteotomies were reviewed. Putative variables included age, weight, gender, and breed. Surgery date, delay before distraction, rate and duration of distraction, mechanical complications, and frame removal date were recorded. Radiographic data included bone operated, bone length, osteotomy site, bone and limb size at osteotomy site, distraction distance, and CEF frame size and stiffness.

RESULTS

Mean ± SD bone consolidation period was 56 ± 33 days. Mean duration of external fixation was 77 ± 35 days. Twelve fixation failures occurred. Radii healed faster than tibiae (P < .001). Failure of fixation (P = .002) and stiff frames (P = .033) increased duration of bone consolidation. For the tibia, durations of bone consolidation and external fixation decreased with larger bone size relative to limb size (P = .004). For the radius, bone consolidation duration decreased as distraction amount increased (P = .03).

CONCLUSION

Radii healed faster than tibiae. Wearing frames with low or moderate stiffness, the absence of mechanical complications, a larger distraction distance, and a larger bone size accelerated bone consolidation. Optimizing these factors should accelerate bone consolidation and reduce the duration of external fixation.