Patient-specific finite element modeling for fracture risk prediction in a canine model of osteosarcoma.

Background: In cancer patients with bone tumors, pathological fractures are a major concern. Making treatment decision for these patients requires an evaluation of fracture risk, which is currently based on semi-qualitative criteria that lack patient-specificity. Because of this, there exists a need for quantitative fracture risk prediction tailored to the patient's individual bone geometry. To address this need, this study aims to develop and validate a finite element (FE) technique that can be used to create patient-specific models and more accurately identify fracture risk. Model validation was performed using canine radii. Methods: Radii were harvested from eight canines euthanized for reasons unrelated to the study. A semicircular osteotomy was made in the distal portion of each bone to simulate tumor lysis. Samples underwent computed tomography (CT) scanning and were randomly assigned to loading groups for destructive mechanical testing. Three samples were tested in torsion, three in cantilever bending, and two in compression. FE models were created for each bone from the corresponding CT scan to replicate patient-specific geometry. Material properties were based on equations relating scan properties to elastic modulus. Boundary conditions and loads were added to the models based on the sample's treatment group. Stiffness and strain data were collected from both the mechanical testing and FE simulation, and yield load predictions were made based on maximum principal strain. Experimental and computational results were compared using a linear regression. Results: The FE models were most accurate in predicting stiffness, followed by strain, with yield load having the lowest accuracy. Linear regressions resulted in R2 values of 0.9335 for bending and compression and 0.8798 for torsion. Conclusions: The proposed FE technique is a valid method for predicting fracture in a canine model of osteosarcoma. This method could provide patient-specific, quantitative data to aid clinicians in decisions regarding surgical intervention for patients with bone tumors.

Updates in Surgical Oncology.

New knowledge and data can influence the treatment options of dogs and cats affected by neoplasms. Partial limb amputation with the use of a prosthesis is possible in dogs. Newer studies attempt to define better and understand the complications and limb function associated with this approach. Limb sparing is an alternative to amputation, and three-dimensional printing allows the manufacturing of personalized endoprostheses. Finally, the recommended approach for the excision of cutaneous mast cell tumors (MCTs) is with proportional margins. In dogs, grade shifting might have occurred when removing a recurrent MCT or soft tissue sarcoma.

Oclacitinib and Myxoma Virus Therapy in Dogs with High-Grade Soft Tissue Sarcoma.

Human rhabdomyosarcomas are rarely cured by surgical resection alone. This is also true for high-grade soft tissue sarcomas in dogs. Dogs with spontaneous sarcoma are good models for clinical responses to new cancer therapies. Strategic combinations of immunotherapy and oncolytic virotherapy (OV) could improve treatment responses in canine and human cancer patients. To develop an appropriate combination of immunotherapy and OV for dogs with soft tissue sarcoma (STS), canine cancer cells were inoculated with myxoma viruses (MYXVs) and gene transcripts were quantified. Next, the cytokine concentrations in the canine cancer cells were altered to evaluate their effect on MYXV replication. These studies indicated that, as in murine and human cells, type I interferons (IFN) play an important role in limiting MYXV replication in canine cancer cells. To reduce type I IFN production during OV, oclacitinib (a JAK1 inhibitor) was administered twice daily to dogs for 14 days starting ~7 days prior to surgery. STS tumors were excised, and MYXV deleted for serp2 (MYXV∆SERP2) was administered at the surgical site at two time points post-operatively to treat any remaining microscopic tumor cells. Tumor regrowth in dogs treated with OV was decreased relative to historical controls. However, regrowth was not further inhibited in patients given combination therapy.

Prospective evaluation of canine partial limb amputation with socket prostheses.

BACKGROUND: Canine prostheses have been commercially available for many years but are still in early stages of research, development, and clinical application. OBJECTIVE: To prospectively investigate mid-term clinical outcomes of partial limb amputation with a socket prosthesis (PLASP) in canine patients via a descriptive prospective clinical case series and to describe a clinical protocol for PLASP. METHODS: Client-owned dogs (n = 12) with distal limb pathology for which total limb amputation was recommended were enrolled. Partial limb amputation was performed and a socket prosthesis was moulded and fitted to the limb. Complications, clinical follow-up, and objective gait analysis (OGA) were recorded for at least 6 months. An online survey was completed by owners after study completion. RESULTS: Ten dogs with thoracic limb pathology and two with pelvic limb pathology were included. The most common site of amputation was mid-radius (n = 5). Eleven of 12 dogs demonstrated quadrupedal gait on OGA with mean per cent body weight distribution (%BWD) of 26% on thoracic limb prostheses and a %BWD of 16% for the one pelvic limb prosthesis that OGA data were available for. Complications included prosthesis suspension difficulties (n = 5), pressure sores (4), bursitis (4), postoperative infection (3), prosthesis aversion (2), dermatitis (1), and owner noncompliance (1). Two owners elected to discontinue prosthesis use. CONCLUSIONS: PLASP allowed restoration of quadrupedal gait patterns in most patients. Owners reported overall positive satisfaction, though a high complication rate was observed. PLASP should be considered in select cases as an alternative to total limb amputation for dogs with distal limb pathology.

Modified hemipelvectomy techniques in dogs and cats appear well tolerated with good functional outcomes.

OBJECTIVE: To describe the clinical characteristics, procedural techniques, complications, and outcomes of dogs and cats undergoing any of the following modified hemipelvectomy techniques: concurrent partial sacrectomy and/or partial vertebrectomy, osseous excision crossing midline, and reconstruction without the use of local musculature. ANIMALS: 23 client-owned animals (20 dogs and 3 cats) that underwent modified hemipelvectomy techniques. Animals that underwent traditional (nonmodified) hemipelvectomy techniques were excluded. PROCEDURES: The medical records of 3 academic institutions were reviewed, and data were recorded and analyzed. RESULTS: Modified hemipelvectomy was performed with partial sacrectomy and/or vertebrectomy in 11 dogs, excision crossing pelvic midline with concurrent limb amputation in 5 dogs and 2 cats, and closure without use of native muscle or mesh in 4 dogs and 1 cat. Surgery was performed for tumor excision in all cases. Excision was reported as complete in 16 of 23, incomplete in 6 of 23, and not recorded in 1 of 23 animals. All animals survived to discharge. Only animals undergoing partial sacrectomy/vertebrectomy (4/11) experienced postoperative mobility concerns. Major intra- or post-operative complications (grades 3 and 4) occurred in 2 dogs that underwent partial sacrectomy/vertebrectomy, and 1 of these animals experienced a complication that resulted in death. The median time to death or last follow-up was 251 days (range, 3 to 1,642). CLINICAL RELEVANCE: The modified hemipelvectomy techniques reported in this cohort were overall well tolerated with good functional outcomes. These findings support the use of these modified hemipelvectomy techniques in dogs and cats, and previous notions regarding tolerable hemipelvectomy procedures should be reconsidered. However, additional studies with larger numbers of patients undergoing modified hemipelvectomy techniques are needed to gain more information.

Grade shifts in recurrent canine soft tissue sarcomas and mast cell tumors.

OBJECTIVE: To determine the incidence of histologic grade shift (alteration of grade relative to the original tumor) in recurrent canine soft tissue sarcoma (STS) and mast cell tumor (MCT), and to determine the level of agreement between blinded pathologist review and original histology interpretation of STS and MCT grades. ANIMALS: 15 dogs with recurrent cutaneous/subcutaneous STS and 5 dogs with recurrent cutaneous MCT. All included dogs underwent excision of both the primary and recurrent tumors and had tumor samples available for review. PROCEDURES: The medical records and histology database from a single institution were reviewed, and data were recorded and analyzed. A single board-certified veterinary pathologist performed blinded evaluation of all excisional tumor samples, including both primary and recurrent disease, and these were evaluated independently and in conjunction with initial pathologic diagnoses. RESULTS: Based on single pathologist review, 7 of 15 (46.7%) dogs with recurrent STS had grade shift characterized by a higher or lower recurrent tumor grade in 4 of 7 and 3 of 7 cases, respectively, and 1 of 5 dogs with recurrent MCT had grade shift characterized by an increased grade of the recurrent tumor. Variability in reported grade between original histology report and pathologist review occurred for 13 of 30 (43.3%) STS excisional biopsy samples and 0 of 10 MCT excisional biopsy samples. CLINICAL RELEVANCE: Grade shift has been reported in multiple tumor types in people and has the potential to alter prognosis and treatment recommendations. This is the first study to document this phenomenon in dogs. Additional large-scale studies are needed to determine factors associated with grade shift as well as prognostic significance of grade shift for recurrent canine STS and MCT.

Lymphotropic nanoparticle magnetic resonance imaging for diagnosing metastatic lymph nodes in dogs with malignant head and neck tumours.

Lymphotropic nanoparticle magnetic resonance imaging (LNMRI) utilises ultrasmall paramagnetic iron nanoparticles (USPIOs) for imaging of metastatic lymph nodes in patients afflicted with cancer. LNMRI has been shown to be a highly effective and accurate way to diagnose metastasis in humans but has not been commonly reported on in veterinary medicine. USPIOs are phagocytised by macrophages and then localised to lymph nodes where they create a susceptibility artefact on gradient echo MRI sequences. In this study dogs (n = 24) with naturally occurring head and neck tumours were imaged with LNMRI then had mandibular and retropharyngeal lymph nodes extirpated for histological analysis. Subjective and objective analysis of the LNMRI images was performed and imaging results compared to histology as the gold standard. A total of 149 lymph nodes were included in this study. The overall sensitivity, specificity and accuracy was 64%, 94.4% and 89.3% respectively. However, if dogs with mast cell tumours were excluded from analysis the sensitivity, specificity and accuracy rose to 85.7%, 95.7% and 94.6%. LNMRI is potentially an accurate way to determine the presence of lymph node metastasis in dogs with some types of head and neck tumours. However, LNMRI has only moderate accuracy in dogs with oral or mucocutaneous mast cell tumours in this region.

Muscular morphometric study of the canine shoulder for the design of 3D-printed endoprostheses in dogs with osteosarcoma of the proximal humerus: a pilot cadaveric study by MRI.

OBJECTIVE: Osteosarcoma frequently affects the proximal humerus in dogs. In veterinary medicine, no therapeutic option for the treatment of osteosarcoma satisfactorily preserves limb function. 3D-printed personalized endoprosthesis offers a promising treatment option. Morphometric data, necessary for the design of the endoprosthesis, are currently lacking in canine patients. Our objective was to acquire the morphometric data necessary to refine the design of the endoprosthesis. ANIMAL: A single canine cadaveric thoracic limb. PROCEDURES: Sagittal proton-density, and sagittal, dorsal, and transverse T1-weighted sequences of the thoracic limb were acquired with a 1.5 Tesla Magnetic Resonance Imaging (MRI) unit. Nineteen muscles of interest were subsequently identified using medical imaging software (Mimics©) and their volume was reconstructed in 3D using computer-aided design (CATIA©). Mormophetric data were recorded for each of the 19 muscles. The same canine cadaver was then dissected to measure the same parameters. RESULTS: All muscles were successfully identified with data consistent with the dissected cadaveric data. Certain muscles were more challenging to isolate on MRI, namely the heads of the triceps brachii, superficial pectoral, and latissimus dorsi. The relative distribution of muscle volumes was similar to historical data. Muscle tissue density was not significantly affected by freezing (1.059 g/cm3). CLINICAL RELEVANCE: MRI is a useful tool to collect morphometric data but imperfect if used alone. This approach was the first attempt to validate more general morphometric data that could be used to refine the design of custom 3D-printed prostheses for limb-sparing of the proximal humerus. Further imaging studies are warranted to refine our model.

Configuration of pathologic fractures in dogs with osteosarcoma following stereotactic body radiation therapy: A retrospective analysis.

For some cases of canine appendicular osteosarcoma (OSA), limb-sparing treatment options are often desired, one of which is stereotactic body radiation therapy (SBRT). A major complication of SBRT is fracture of the irradiated bone at the site of treatment. The present study evaluated 127 appendicular OSA sites in 122 dogs treated with SBRT to identify the most common pathologic fracture locations and configurations. A total of 50 tumours experienced a pathologic fracture, and 38 had imaging sufficient to identify fracture configuration. The distal tibia was more likely to develop a fracture than other sites. Multiple types of fracture configuration (transverse, oblique, spiral and comminuted) were observed. The distal radius was significantly more likely to develop a transverse fracture than other sites. Documentation of fracture location and configuration leads to the identification of the forces contributing to fracture occurrence, since each configuration is a result of different forces acting on each affected bone. Such knowledge is imperative for the development of new approaches to diminish the occurrence of pathologic fractures.

Sternohyoideus-sternothyroideus muscle flap to reconstruct oronasal fistulas due to maxillary cancer in four dogs.

OBJECTIVE: To describe the repair of oronasal fistulas in dogs treated for maxillary cancer, with a novel sternohyoideus-sternothyroideus muscle flap, and to report the outcome. ANIMALS: Client-owned dogs (n = 4) with oronasal fistulas related to cancer. STUDY DESIGN: Short case series. METHODS: Maxillary defects were caused by tissue destruction by the tumor and tumor response to radiation therapy in two cases and a complication of caudal maxillectomy in two cases, one of which had neoadjuvant radiation therapy. All tumors were >4 cm at the level of the maxilla. Flaps were harvested by transecting the ipsilateral sternothyroideus and sternohyoideus muscles from their origin at the manubrium and costal cartilage. The muscles were rotated around the base of the cranial thyroid artery and tunneled subcutaneously in the neck and through an incision in the caudodorsal aspect of the oral cavity. The muscle flap was sutured to the edges of the oronasal fistula. RESULTS: The flap reached as far rostral as the level of the first premolar without tension. All dogs had clinical signs that improved postoperatively. All dogs had partial dehiscence of the flap. CONCLUSION: This flap was associated with a high rate of complications; however, all flaps were used in challenging cases. Clinical signs related to oronasal fistula were improved in all dogs in this case series.

Outcomes in dogs undergoing surgical stabilization and non-stereotactic radiation therapy for axial and appendicular bone tumors.

Background: Information on dogs that undergo radiation therapy (RT) with non-stereotactic protocols in addition to surgical stabilization with implant placement for treatment of bone tumors is limited. Objective: Our primary objectives were to describe the clinical characteristics as well as short- and long-term outcomes, including complications, function, and disease progression, in dogs that underwent both surgical stabilization with implant placement and non-stereotactic RT for local treatment of a bone tumor. Methods: A bi-institutional retrospective case series was performed. Animals: Eight client-owned dogs that underwent both surgical stabilization with implant placement and non-stereotactic RT for local treatment of a bone tumor were included. Results: Tumor types included osteosarcoma or suspected osteosarcoma (5), plasma cell tumor (2), and grade 3 fibrosarcoma (1). Radiation protocols were hypofractionated (palliative intent) in 5 dogs and fractionated (definitive intent) in 3 dogs. Five dogs experienced complications following both RT and surgery, including grade 1 complications in two dogs, a grade 2 complication in one dog, both grade 1 and 2 complications in one dog, and both grade 2 and 3 complications in one dog. Clinical signs subjectively improved in all dogs that had outcomes relative to function documented post-surgery/RT (7). Of these 7 dogs, 4 maintained long-term improvement in function and clinical signs, whereas 3 experienced subsequent recurrence/progression of clinical signs at a median of 133 days (range 91-186) postoperatively in association with biomechanical complications (screw loosening), surgical site infection, and local disease progression in 1 dog each; subsequent treatment resulted in improved clinical signs for each of these 3 dogs, such that overall good long-term functional outcomes were experienced. No dogs required amputation or additional vertebral surgery as salvage for local disease control or palliation. The median progression free interval was 206 days (range 25-1078), and the median survival time was 253 days (range 122-1078) with 1 additional dog lost to follow-up at 575 days. Two dogs experienced local disease progression, and 6 dogs experienced systemic disease progression; both dogs that developed local disease progression received palliative intent RT protocols. Clinical relevance: In this cohort, dogs with primary bone tumors that underwent surgical stabilization with implant placement and hypofractionated or fractionated non-stereotactic RT for local treatment had a low incidence of major complications, good limb function and ambulation post-treatment, and relatively prolonged survival times despite disease progression.

Potential Seeding From Fine-Needle Aspiration of an Axial Osteosarcoma: A Case Report.

This report describes the first potential case of seeding after fine-needle aspiration (FNA) of a rib osteosarcoma in a dog. An 8-year-old, 28-kg female spayed Golden Retriever was presented to her primary veterinarian with a 3-week history of a 3-cm firm, unpainful, immobile mass arising from the 9th rib. The mass was aspirated and submitted for cytological examination. A subcutaneous nodule developed several days after the FNA was performed in a location immediately overlying but distinct from the primary rib tumor on palpation. Both the primary mass and the newly diagnosed subcutaneous nodule were biopsied and were consistent with an osteosarcoma. Although it cannot be ruled out that the subcutaneous lesion was metastatic, seeding was a reasonable explanation based on where the new mass was located and how quickly it appeared after the FNA was performed. The aim of this case report was to describe the possibility of tumor seeding during FNA for osteosarcoma. It is the authors' opinion that utility of cytological diagnosis of bone tumors outweighs the risk of possible seeding and should continue to be used as a routine diagnostic test for the diagnosis of aggressive bone lesions.

B7-H3 Specific CAR T Cells for the Naturally Occurring, Spontaneous Canine Sarcoma Model.

One obstacle for human solid tumor immunotherapy research is the lack of clinically relevant animal models. In this study, we sought to establish a chimeric antigen receptor (CAR) T-cell treatment model for naturally occurring canine sarcomas as a model for human CAR T-cell therapy. Canine CARs specific for B7-H3 were constructed using a single-chain variable fragment derived from the human B7-H3-specific antibody MGA271, which we confirmed to be cross-reactive with canine B7-H3. After refining activation, transduction, and expansion methods, we confirmed target killing in a tumor spheroid three-dimensional assay. We designed a B7-H3 canine CAR T-cell and achieved consistently high levels of transduction efficacy, expansion, and in vitro tumor killing. Safety of the CAR T cells were confirmed in two purposely bred healthy canine subjects following lymphodepletion by cyclophosphamide and fludarabine. Immune response, clinical parameters, and manifestation were closely monitored after treatments and were shown to resemble that of humans. No severe adverse events were observed. In summary, we demonstrated that similar to human cancers, B7-H3 can serve as a target for canine solid tumors. We successfully generated highly functional canine B7-H3-specific CAR T-cell products using a production protocol that closely models human CAR T-cell production procedure. The treatment regimen that we designed was confirmed to be safe in vivo. Our research provides a promising direction to establish in vitro and in vivo models for immunotherapy for canine and human solid tumor treatment.

Personalized endoprostheses for the proximal humerus and scapulohumeral joint in dogs: Biomechanical study of the muscles' contributions during locomotion.

Osteosarcoma represents one of the most common bone tumours in dogs. It commonly occurs in the proximal humerus, the most affected anatomic site. Until recently, amputation or limb-sparing surgery leading to an arthrodesis coupled with chemotherapy were the only available treatments, but they often lead to complications, reduced mobility and highly impact dog's quality of life. Prototypes of both articulated and monobloc (no mobility) patient-specific endoprostheses have been designed to spare the limb afflicted with osteosarcoma of the proximal humerus. This study focuses on the biomechanical effects of endoprostheses and shoulder muscle kinematics. For each of the endoprosthesis designs, a minimal number of muscles needed to ensure stability and a certain degree of joint movement during walking is sought. A quasi-static study based on an optimization method, the minimization of the sum of maximal muscle stresses, was carried out to assess the contribution of each muscle to the shoulder function. The identification of the most important muscles and their impact on the kinematics of the prosthetic joint lead to an improvement of the endoprosthesis design relevance and implantation feasibility.

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.

Biological behaviour of primary osteosarcoma of the digits, metacarpal and metatarsal bones in dogs.

Osteosarcoma (OSA) arising from the digits, metatarsal and metacarpal bones is rare and may carry a better prognosis compared with other locations. The aim of this study was to retrospectively evaluate the biological behaviour, the progression free interval (PFI), the survival time (ST) and evaluate the effect of adjuvant chemotherapy for OSA affecting these bones. Medical records from two academic institutions were reviewed and 15 cases were included. Descriptive statistics were used for signalment and history. For estimation of median PFI and median ST, the Kaplan-Meier method was utilized. The prognostic effect of chemotherapy, lymphocyte and monocyte count was investigated. Log-rank analysis was used to compare PFI and ST between groups. The overall median PFI and median ST were 377 and 687 days, respectively. No significant differences were noted for any of the variables evaluated. In this study, dogs affected by OSA of digits, metacarpal and metatarsal bones appear to have a longer ST compared with dogs with OSA of other appendicular locations. A study with a larger number of patients is needed to confirm these results and investigate the potential benefit of adjuvant chemotherapy.

Outcomes of cats treated with maxillectomy: 60 cases. A Veterinary Society of Surgical Oncology retrospective study.

Maxillectomy is poorly described for the management of oral tumours in cats and is occasionally not recommended because of the high complication rate and sub-optimal outcome reported in cats treated with mandibulectomy. The purpose of this study was to retrospectively evaluate the complications and oncologic outcome in cats treated with maxillectomy. Sixty cats were included in the study. Maxillectomy procedures included unilateral rostral (20.0%), bilateral rostral (23.3%), segmental (10.0%), caudal (20.0%) and total unilateral maxillectomy (26.7%). Intra-operative and post-operative complications were reported in 10 (16.7%) and 34 (56.7%) cats, respectively. The most common post-operative complications were hyporexia (20.0%) and incisional dehiscence (20.0%). The median duration of hyporexia was 7 days. Benign tumours were diagnosed in 19 cats (31.7%) and malignant tumours in 41 cats (68.3%). Local recurrence and metastatic rates were 18.3% and 4.9%, respectively; the median progression-free interval (PFI) was not reached. The disease-related median survival time was not reached overall or for either benign or malignant tumours. The 1- and 2-year survival rates were, respectively, 100% and 79% for cats with benign tumours, 89% and 89% for cats with malignant tumours, 94% and 94% for cats with fibrosarcomas, 83% and 83% for cats with squamous cell carcinomas, and 80% and 80% for cats with osteosarcomas. Poor prognostic factors included mitotic index for PFI, adjuvant chemotherapy for both PFI and survival time, and local recurrence for survival time. Maxillectomy is a viable treatment option for cats resulting in good local tumour control and long survival times.

Effect of perioperative desmopressin in cats with mammary carcinoma treated with bilateral mastectomy.

Perioperative administration of desmopressin has shown to significantly decrease rates of local recurrence and metastasis, and increase survival times in dogs with grade II and III mammary carcinomas. The objective of this study was to compare the oncologic outcome of cats with mammary carcinoma treated with bilateral mastectomy with or without perioperative administration of desmopressin. Medical records from nine veterinary institutions were searched to identify cats diagnosed with mammary carcinoma treated with bilateral mastectomy. Sixty cats treated with single-session or staged bilateral mastectomy were included. There were no significant differences in oncologic outcomes found between cats treated and not treated with desmopressin. No adverse effects were seen in any of the cats treated with perioperative desmopressin. Postoperative complications occurred in 18 cats (38.3%) treated with single-session bilateral mastectomy and in three cats (23.1%) treated with staged bilateral mastectomy (P = .48). Histologic grade and a modification of a proposed five-stage histologic staging system were both prognostic for disease-free interval. Incomplete histologic excision was associated with significantly increased rates of metastasis and tumour progression, and a shorter median survival time (MST). Cats that developed local recurrence also had a significantly shorter MST. The results of this study do not support the use of perioperative desmopressin to improve outcome when performing bilateral mastectomy for the treatment of mammary carcinoma in cats.

Safety and efficacy of stereotactic body radiation therapy (SBRT) for the treatment of canine thyroid carcinoma.

Thyroid carcinoma develops spontaneously in dogs, with only 25% to 50% of cases amenable to surgery at diagnosis. Local control for unresectable tumours can be provided with external beam radiotherapy. The aim of this retrospective study is to describe the safety and efficacy of stereotactic body radiation therapy (SBRT) for treatment of canine thyroid carcinoma. Twenty-three dogs met inclusion criteria; median tumour volume before SBRT was 129.9 cm3 (range, 2.7-452.8 cm3 ). Sixteen patients (70%) had unresectable tumours. Pulmonary metastasis was present or suspected in 10 patients (44%) before SBRT. Patients were prescribed 15 to 40 Gy to targeted tumour volume in one to five fractions. Twenty patients evaluated had overall response rate of 70% (complete response, n = 4; partial response, n = 10). Thirteen out of sixteen (81%) symptomatic patients had clinical improvement within a median time of 16 days (range, 2-79 days). Median progression free survival (MPFS) was 315 days. Median survival time (MST) was 362 days. Nine patients (39%) had grade 1 acute radiation toxicity. Three patients had grade 1 late radiation toxicity (two leukotrichia and one [4%] with intermittent cough). Responders had significantly longer MPFS (362 vs 90 days; HR 4.3; 95% CI 1.4-13.5; P = .013) and MST (455 vs 90 days; HR 2.9; 95% CI 1-8.4; P = .053). Presenting with metastasis was not a significant negative prognostic factor (MST 347 vs 348 days without metastasis; P = .352). SBRT is a safe and effective treatment modality for non-resectable canine thyroid carcinoma.

Canine tonsillar neoplasia and tonsillar metastasis from various primary neoplasms.

Tonsillar metastasis from distant primary tumours has not been described in dogs, and reports are rare in humans. The aims of this study were to determine whether tumour metastasis occurs to the canine palatine tonsils and evaluate whether afferent lymphatics drain to the palatine tonsils via skull indirect computed tomography lymphangiography (ICTL). Retrospective review of the diagnostic laboratory tonsillar histopathology submissions was performed. ICTL studies (n = 53) were retrospectively reviewed by a single radiologist. Of 882 total tonsil histopathology samples, 492 (56%) were considered neoplastic, with 8% of them benign. Of the primary malignant neoplasms of the tonsil, squamous cell carcinoma (55%), lymphoma (17%) and melanoma (12%) were most common. Tonsillar metastasis was confirmed in 41 cases; histopathologic evaluation revealed melanoma (25), carcinoma (10), hemangiosarcoma (2) and one each of fibrosarcoma, malignant histiocytosis, basal cell tumour and undifferentiated sarcoma. A total of 53 tonsillar melanoma cases were identified, of which 25 represented metastasis from a known distant primary tumour and 28 were solely tonsillar, with 9 of these cases having concurrent lymph node metastasis. No ICTL cases had lymphatic contrast drainage to the palatine tonsil. The palatine tonsil is an important site of metastasis for a variety of primary tumour types from many locations. ICTL did not reveal lymphatics draining to the palatine tonsil, which is highly supportive of hematogenous route of metastasis to the tonsil. Tonsillar metastasis may be more common than previously thought. It is recommended to perform a thorough oral examination, including the tonsils, for all oral tumours and melanoma cases.