Retrospective evaluation of toceranib phosphate (Palladia®) use in the treatment of inoperable, metastatic, or recurrent canine pheochromocytomas: 5 dogs (2014-2017)

Retrospective evaluation of toceranib phosphate (Palladia) use in the treatment of feline pancreatic carcinoma

Objective

To retrospectively assess the biological response in cats with pancreatic carcinoma treated with toceranib phosphate.

Animals

Twenty-six client-owned cats.

Procedure

Patient information from multiple institutions was solicited via an emailed REDCap survey. For inclusion, cats were required to have a confirmed diagnosis of exocrine pancreatic carcinoma either by histopathology, cytology, or both; to have received treatment with toceranib phosphate; and to have adequate follow-up data for analysis.

Results

Twenty cats were treated for gross disease and 6 for microscopic disease/incomplete margins. Clinical benefit (complete response, partial response, or stable disease ≥ 10 wk) was observed in 9/20 cats treated in the gross disease setting (45%; complete response: n = 1, stable disease: n = 8). The remaining 11 cats with gross disease did not respond to toceranib phosphate. In the cats with microscopic disease, response was mixed. The median survival time for all cats was 97 d (range: 1 to 1666 d).

Conclusion

Toceranib phosphate was well-tolerated and provided modest clinical benefit to a subset of cats treated.

Clinical relevance

Although feline exocrine pancreatic carcinoma continues to be a challenging disease to treat, toceranib phosphate appeared to provide potential clinical benefit.

Toceranib phosphate and firocoxib-mediated partial response in a dog with advanced intranasal sarcoma

A nine-year-old, castrated male mixed-breed dog presented with a three-month history of sneezing and stertorous breathing. Computed tomography revealed a soft tissue mass in the left nasal cavity with lysis of the cribriform plate. The mass was diagnosed as intranasal sarcoma based on histopathological analysis. The tumor cells were immunohistochemically positive for KIT and platelet-derived growth factor receptor α/β and negative for vascular endothelial growth factor receptor 2 and cyclooxygenase-2. Treatment with toceranib phosphate (TOC) and firocoxib reduced the tumor size, which was defined as partial response (PR). After PR induction, TOC alone mediated survival for 205 days. This case report suggests that the combination of TOC and possibly firocoxib may be a therapeutic option for canine intranasal sarcoma.

Whole transcriptome analysis of canine pheochromocytoma and paraganglioma

Pheochromocytomas and paragangliomas (PPGLs) are neuroendocrine tumors arising from the chromaffin cells in the adrenal medulla and extra-adrenal paraganglia, respectively. Local invasion, concurrent disorders, and metastases prevent surgical removal, which is the most effective treatment to date. Given the current lack of effective medical treatment, there is a need for novel therapeutic strategies. To identify druggable pathways driving PPGL development, we performed RNA sequencing on PPGLs (n = 19) and normal adrenal medullas (NAMs; n = 10) of dogs. Principal component analysis (PCA) revealed that PPGLs clearly clustered apart from NAMs. In total, 4,218 genes were differentially expressed between PPGLs and NAMs. Of these, 232 had a log2 fold change of >3 or < -3, of which 149 were upregulated in PPGLs, and 83 were downregulated. Compared with NAMs, PPGLs had increased expression of genes related to the cell cycle, tumor development, progression and metastasis, hypoxia and angiogenesis, and the Wnt signaling pathway, and decreased expression of genes related to adrenal steroidogenesis. Our data revealed several overexpressed genes that could provide targets for novel therapeutics, such as Ret Proto-Oncogene (RET), Dopamine Receptor D2 (DRD2), and Secreted Frizzled Related Protein 2 (SFRP2). Based on the PCA, PPGLs were classified into 2 groups, of which group 1 had significantly higher Ki67 scores (p = 0.035) and shorter survival times (p = 0.04) than group 2. Increased expression of 1 of the differentially expressed genes between group 1 and 2, pleiotrophin (PTN), appeared to correlate with a more aggressive tumor phenotype. This study has shed light on the transcriptomic profile of canine PPGL, yielding new insights into the pathogenesis of these tumors in dogs, and revealed potential novel targets for therapy. In addition, we identified 2 transcriptionally distinct groups of PPGLs that had significantly different survival times.

Stereotactic body radiation therapy as an alternative to adrenalectomy for the treatment of pheochromocytomas in 8 dogs

The objective of this report is to describe the use and outcome of stereotactic body radiation therapy (SBRT) for treatment of pheochromocytomas in 8 dogs. Pheochromocytomas are an uncommon but challenging tumour to manage. Adrenalectomy is the standard of care for treatment of pheochromocytomas in both animals and humans; however, unpredictable catecholamine secretion from the tumour and vascular and local invasion of the tumour and thrombi can pose life-threatening perioperative and anaesthetic risks. SBRT has been investigated as an alternative to adrenalectomy in human patients with pheochromocytomas. Eight dogs with clinical signs, an adrenal mass, and cytology and/or urine normetanephrine/creatinine ratios consistent with pheochromocytoma were treated with SBRT in lieu of adrenalectomy. Three dogs presented with acute hemoabdomen. Seven dogs had caval tumour invasion, 3 with extension into the right atrium. Following SBRT, all dogs had complete resolution of clinical signs and reduced urine normetanephrine/creatinine ratio and/or tumour size. No significant anaesthetic complications were encountered. Acute radiation toxicity was limited to grade I gastrointestinal signs in 3 dogs and resolved within 1-2 days of symptomatic therapy. Five of 8 dogs were alive at the time of follow up, with a median follow up time of 25.8 months. SBRT resulted in a favourable outcome and mitigated the life-threatening risks of adrenalectomy in these 8 dogs. SBRT may be a safe and effective alternative to adrenalectomy for pheochromocytomas in dogs with non-resectable tumours, or for owners averse to the risks of surgery.

Pharmacokinetics and tolerability of the dual TORC1/2 inhibitor sapanisertib in combination with the MEK inhibitor trametinib in dogs

Activation of one or both the Ras/MAPK and PI3K/Akt/mTOR signal transduction pathways are known to mediate oncogenicity of several canine and human cancers, including mucosal melanomas. Reciprocal cross activation between the two pathways can be a source of drug resistance. Consequently, oral dosing for plasma pharmacokinetic (PK) analysis and tolerability to a combination of sapanisertib, a dual TORC1/2 inhibitor, and trametinib, a MEK inhibitor, was evaluated in nontumor-bearing laboratory dogs for its potential application in parallel pathway targeting. Twelve dogs, divided into three equal cohorts, received either the combination or single agents. Animals were monitored for PK following single dose and 17-day repeat dosing, and by clinical observations, hematology, serum biochemistry, coagulation studies and urinalyses. A single trametinib dose (0.025 mg/kg), sulfated as dimethyl sulfoxide which enhanced its absorption, reached mean maximum concentration (C_max) 0.64 ng/mL [18% coefficient of variation (CV)] at a median time to maximum concentration (T_max) of 1.5 h (hr), and mean area under the concentration-time curve (AUC) 16.8 hr^*ng/mL (14%CV), which were similar when given alone or in combination with sapanisertib. A prolonged half-life afforded 3-4-fold plasma accumulation of trametinib with daily dosing, analogous to humans. Trametinib PK mirrored previous regulatory data in dogs, while exposure approximated some published human values but generally not all patients. Sapanisertib-alone in canine plasma following single 0.1 mg/kg dose [mean C_max 26.3 ng/mL (21%CV), median T_max 2.0 hr, and mean AUC 248 hr^*ng/mL (41%CV)] resembled levels in human therapeutic trials; whereas canine sapanisertib exposure was reduced when combined with trametinib, a known cytochrome P450 CYP3A4 inducer. Sex differences were not observed for either drug. Side effects upon repeat dosing with either or both drugs may include body weight loss, maldigestion, and cutaneous discoloration. The combination was tolerated without dose limiting toxicity, although clinical laboratory analyses revealed drug-induced acute-phase inflammation, proteinuria, and decreased blood reticulocytes, mild changes not necessitating intervention. Short-term results in dogs with this combination would appear to hold translational promise for clinical trial evaluation to target canine and possibly human melanoma, as well as other cancers having one or both signal transduction pathway activations.

Toceranib phosphate in the management of canine insulinoma: A retrospective multicentre study of 30 cases (2009-2019)

BACKGROUND

Insulinomas are the most common tumour of the endocrine pancreas in dogs. These malignant tumours have a high metastatic rate and limited chemotherapeutic options. The multi-receptor tyrosine kinase inhibitor sunitinib malate has benefit in the treatment of metastatic insulinoma in people. Toceranib phosphate, an analogous veterinary agent, may provide benefit for dogs.

METHODS

A retrospective study describing the extent and duration of clinical outcomes and adverse events (AEs) in dogs diagnosed with insulinoma and receiving toceranib.

RESULTS

Records for 30 dogs diagnosed with insulinoma and having received toceranib were identified from a medical record search of five university and eight referral hospitals. The median progression-free interval and overall survival time were 561 days (95% confidence interval (CI): [246, 727 days]) and 656 days (95% CI: [310, 1045 days]), respectively. Of the dogs for which the canine Response evaluation criteria for solid tumours tool could be applied, the majority (66.7%) showed either a complete response, partial response or stable disease. Time to clinical progression was associated with prior intervention and type of veterinary practice. Larger dogs were at increased risk for disease progression and death. No novel AEs were reported.

CONCLUSIONS

Most dogs diagnosed with insulinoma and receiving toceranib appeared to have a clinical benefit. Randomised, prospective studies are needed to better elucidate and objectively quantify the potential effect and survival benefit of toceranib therapy for management of insulinoma in dogs.

Caval chemodectoma in a cat

Case summary

An 11-year-old male neutered domestic shorthair cat was presented with a 4-week history of an intermittent cough and dyspnoea. A pleural effusion was identified, which was confirmed as chyle. Echocardiography and CT revealed a 16 mm mass cranial to the heart, which was invading the cranial vena cava. Because of the location of the mass, it was assumed that chylothorax had developed as a result of direct disruption of the thoracic duct by the tumour or secondarily to central venous hypertension. An exploratory thoracotomy was performed, and the mass, which originated within the wall of the cranial vena cava, was excised with narrow gross margins. Histopathology and immunohistochemistry were consistent with a chemodectoma with residual tumour cells at the surgical margin. Given the residual microscopic disease, adjuvant treatment with toceranib phosphate was initiated. The cat remained well for the duration of treatment and was euthanased 31 months after diagnosis when CT identified recurrent pleural effusion, a heart base mass with cranial vena cava and azygos vein invasion.

Relevance and novel information

Chemodectomas are rare in cats, with only 13 cases reported in the literature to date, and all were located in either the aortic or carotid body. The reported survival with partial resection and/or subtotal pericardiectomy was 13–19 months. Treatment of feline chemodectomas with toceranib phosphate has not been previously reported. To our knowledge, this is the first description of the surgical management of a feline vena cava chemodectoma, combined with adjuvant toceranib phosphate, resulting in a prolonged survival.

The role of toceranib phosphate in dogs with non-mast cell neoplasia: A systematic review

The use of tyrosine kinase inhibitors (TKI) has gained significant importance in veterinary cancer patients over the last decade. Toceranib phosphate has been licensed for the treatment of dogs with mast cell tumours. Its molecular similarity to sunitinib, a TKI used in human medicine, has led many veterinary oncologists to use this agent for multiple neoplastic diseases. The aim of the current study was to perform a systematic review of the evidence for the use of toceranib in dogs with non-mast cell neoplasia. Two electronic databases were searched. Publications were included if toceranib was used as a treatment option in canine patients. Studies and case reports were excluded if toceranib was used as part of a multi-modal treatment plan and response or outcome data related to toceranib therapy were not described. A total of 28 studies were included from 122 references. The most common types of neoplasias identified were neuroendocrine tumours, anal gland sac adenocarcinoma, and osteosarcoma. Multiple other neoplasias had one or two studies identified to describe the use of toceranib. Results of the study support that toceranib phosphate may have efficacy against certain types of neoplasia under certain conditions, such as neuroendocrine tumours, gastrointestinal stromal tumours and anal sac adenocarcinomas, while it is probably not effective for the management of metastatic osteosarcoma based on the findings of the review.

Effective treatment with mitotane for a canine case of presumed ectopic Cushing's syndrome-related pheochromocytoma

Background

In humans, ectopic Cushing's syndrome (ECS) is characterized by hypercortisolemia, which is caused by small lung carcinoma, bronchial carcinoids, and pheochromocytoma. In dogs, only a few cases of ECS associated with pheochromocytoma have been reported to date.

Case Description

Herein, we describe a canine case of malignant pheochromocytoma that is presumed to be the cause of ECS. An 11-year-old, castrated, male Toy Poodle with hypercortisolemia was diagnosed with an adrenal tumor (AT) and treated with mitotane. Although repeated adrenocorticotropic hormone stimulation tests revealed improvement in the dog's condition by mitotane treatment, its condition started declining 197 days post-diagnosis, and he died on day 280. The necropsy revealed the AT was a pheochromocytoma, not an adrenocortical tumor. However, because of no pathological change in the pituitary gland and the other adrenal gland, pheochromocytoma was presumed to be the cause of ECS.

Conclusion

This is the first report that describes the effectiveness of mitotane against presumed ECS-related pheochromocytoma.

C-kit, flt-3, PDGFR-β, and VEGFR2 expression in canine adrenal tumors and correlation with outcome following adrenalectomy

The objective of this retrospective study was to evaluate the expression of receptor tyrosine kinases (RTKs) in canine adrenal tumors and correlate this expression with features of tumor aggressiveness and survival in dogs undergoing adrenalectomy. Forty-three canine adrenal tumors were evaluated for expression of c-kit, fms-like tyrosine kinase 3 (flt-3), platelet-derived growth factor receptor-β (PDGFR-β), and vascular endothelial growth factor receptor 2 (VEGFR2) using immunohistochemistry. Tumor RTK staining characteristics were compared to normal adrenals. Medical records were reviewed for data regarding patient outcome and tumor characteristics. Expression of c-kit, flt-3, PDGFR-β, and VEGFR2 was detected in 26.9%, 92.3%, 96.2%, and 61.5% of cortical tumors and 0%, 63.2%, 47.4%, and 15.8% of pheochromocytomas, respectively. Expression of RTKs was not significantly increased when compared to normal adrenals and did not correlate with survival after adrenalectomy. Receptor tyrosine kinases are not overexpressed in canine adrenal tumors compared to normal adrenal tissue. Therapeutic inhibition of these receptors may still represent an effective approach in cases where receptor activation is present.

Toceranib phosphate (Palladia) for the treatment of canine exocrine pancreatic adenocarcinoma

Background

Canine pancreatic carcinoma is a rare, aggressive tumour that is often diagnosed late in the course of disease. Effective treatment strategies have been elusive, and overall survival time is short. In humans, treatment with tyrosine kinase inhibitors alone, or in combination with IV gemcitabine, have been moderately effective. As canine and human pancreatic carcinomas share many clinical aspects, strategies that mimic human treatment regimens may confer a better outcome in canine patients. The aim of this study was to assess the role of the veterinary tyrosine kinase inhibitor, toceranib phosphate, in the treatment of cytologically or histologically confirmed canine pancreatic carcinomas.

Results

Retrospectively, medical records of dogs with confirmed pancreatic carcinoma treated with toceranib were reviewed. Eight dogs were identified that fit the inclusion criteria. Toceranib was well-tolerated by all patients. Six were treated in the gross disease setting. Four had image-based evaluation of clinical benefit (complete response, partial response, or stable disease of > 10 weeks). Of those patients, 1 achieved a partial response, 2 stable disease, and 1 had progressive disease, for an overall clinical benefit rate of 75 %. An additional dog had clinically stable disease that was not confirmed via imaging. The toceranib-specific median overall survival time was 89.5 days (range: 14–506 days).

Conclusions

Although limited in patient number, this small study suggests that toceranib may have biologic activity in dogs with pancreatic carcinoma. Larger, prospective studies are needed to confirm these preliminary results and define the use of toceranib in the microscopic disease setting.

Evaluation of palliative therapy, alone or in combination with toceranib phosphate, in dogs diagnosed with metastatic or recurrent beta-cell neoplasia

AIMS

To compare survival in dogs with recurrent or metastatic insulinomas that were treated with palliative therapy, alone or in combination with toceranib phosphate and to assess tolerability of the combined therapy in dogs.

MATERIALS AND METHODS

Dogs diagnosed with insulinoma were retrospectively identified in the records of the Veterinary Teaching Hospital Complutense (Madrid, Spain). Diagnosis of insulinoma was based on clinical signs of hypoglycaemia, concentrations in serum of glucose <3.3 mmol/L and insulin >10 μIU/mL and presence of a pancreatic mass on diagnostic imaging. Dogs were treated surgically or medically, according to clinical stage established by imaging techniques, and monitored with blood and urine analyses monthly and abdominal ultrasonography every 3 months until death. Dogs that presented with metastatic disease at diagnosis or with recurrent hypoglycaemia after surgery were treated, according to the owner's decision, with one of two treatment protocols: palliative therapy alone (control group, n=7: diet, prednisone, famotidine or omeprazole, ±octreotide) or palliative therapy in combination with toceranib (treatment group, n=5; median dose of toceranib 2.52 mg/kg). Overall survival time (OST) and adverse events were compared between the two treatment groups.

RESULTS

The OST was longer in the treatment group (median 399, min 125, max 476 days) compared to the control group (median 67, min 23, max 387 days; p=0.042). Dogs in the treatment group had a higher incidence of grade 1-2 gastrointestinal toxicity (diarrhoea) than dogs in the control group (p=0.010). In all cases, gastrointestinal toxicity was solved by temporarily discontinuing toceranib.

CONCLUSIONS AND CLINICAL RELEVANCE

The use of toceranib combined with palliative treatment in dogs with suspect metastatic or recurrent insulinomas increased survival time and was adequate tolerated.

Precursor-targeted immune-mediated anemia in a dog with a stage IV mast cell tumor and bone marrow infiltration

A 12-year-old spayed female Shiba Inu dog was referred to our hospital for a suspected mast cell tumor (MCT) of the bone marrow (BM). Laboratory abnormalities included severe nonregenerative anemia (packed cell volume or PCV: 12.5%; reference interval (RI): 37.3-61.7%; reticulocytes: 35.1 × 10³ /µL; RI: 10-110 × 10³ /µL), and a few mast cells were visualized in the blood smear examination. The BM was hypercellular with hematopoietic cells, a decreased myeloid:erythroid (M:E) ratio (0.77; RI, 0.9-1.8), and no dysplastic hematopoietic cells. Mast cells accounted for 11.5% of the total nucleated BM cells. Neoplastic mast cells and histiocytes phagocytizing erythroid progenitor cells were occasionally noted. The dog was diagnosed with precursor-targeted immune-mediated anemia (PIMA) concurrent and a stage IV MCT infiltrating the BM. Multimodal treatment included toceranib, imatinib, vinblastine, lomustine (CCNU), prednisolone, cyclosporine, mycophenolate mofetil, and a blood transfusion. The dog died due to MCT progression lasting 139 days after the initial BM examination. To the best of our knowledge, this is the first report of a dog presenting with PIMA and a stage IV MCT infiltrating the BM.

Transcriptome of Two Canine Prostate Cancer Cells Treated With Toceranib Phosphate Reveals Distinct Antitumor Profiles Associated With the PDGFR Pathway

Canine prostate cancer (PC) presents a poor antitumor response, usually late diagnosis and prognosis. Toceranib phosphate (TP) is a nonspecific inhibitor of receptor tyrosine kinases (RTKs), including vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR), and c-KIT. This study aimed to evaluate VEGFR2, PDGFR-β, and c-KIT protein expression in two established canine PC cell lines (PC1 and PC2) and the transcriptome profile of the cells after treatment with TP. Immunofluorescence (IF) analysis revealed VEGFR2 and PDGFR-β protein expression and the absence of c-KIT protein expression in both cell lines. After TP treatment, only the viability of PC1 cells decreased in a dose-dependent manner. Transcriptome and enrichment analyses of treated PC1 cells revealed 181 upregulated genes, which were related to decreased angiogenesis and cell proliferation. In addition, we found upregulated PDGFR-A, PDGFR-β, and PDGF-D expression in PC1 cells, and the upregulation of PDGFR-β was also observed in treated PC1 cells by qPCR. PC2 cells had fewer protein-protein interactions (PPIs), with 18 upregulated and 22 downregulated genes; the upregulated genes were involved in the regulation of parallel pathways and mechanisms related to proliferation, which could be associated with the resistance observed after treatment. The canine PC1 cell line but not the PC2 cell line showed decreased viability after treatment with TP, although both cell lines expressed PDGFR and VEGFR receptors. Further studies could explain the mechanism of resistance in PC2 cells and provide a basis for personalized treatment for dogs with PC.

Toceranib phosphate in the treatment of canine thyroid carcinoma: 42 cases (2009-2018)

Thyroid carcinoma is the most common endocrine malignancy in dogs. Thyroidectomy and radiation therapy control local disease, yet are not always feasible, and efficacious medical therapies need to be identified. Toceranib phosphate has been reported to provide clinical benefit (CB) in dogs with thyroid carcinoma, while its role in treatment-naïve thyroid tumours has not been well-described. The objective of this study was to describe the use of toceranib in the management of thyroid carcinomas in dogs in both the naïve-disease and prior therapy- settings. A medical record search identified 42 dogs diagnosed with thyroid carcinoma and treated with toceranib, of which 26 and 16 dogs were in settings of naïve-disease and after prior therapy, respectively. Twenty-three (88.4%) and twelve (75%) dogs experienced CB in the naïve and prior therapy settings, respectively. The median [95% confidence interval] progression free interval (PFI) for dogs in the naïve and prior therapy settings were 206 [106,740] and 1015 [92,1015] days, respectively. The median overall survival time (OST) for dogs in the naïve and prior therapy settings were 563 [246,916] and 1082 [289,1894] days, respectively. Overall, the data provided no evidence for differences in overall PFI (P > .20) or OST (P = .15) between settings. However, when asymptomatic at the time of diagnosis, dogs in the naïve setting showed poorer survival prognosis (estimated hazard ratio 17.2 [1.8, 163]) relative to dogs in the prior therapy setting. This study characterizes PFI, OST and CB with minimal AE in dogs with thyroid carcinoma treated with toceranib in both the naïve and prior therapy settings.

Favorable outcome of pheochromocytoma in a dog with atypical Cushing's syndrome and diabetes mellitus following medical treatment: a case report

Background

Pheochromocytoma (PCC) has poor prognosis and adrenalectomy is hard to be performed, in case of caudal vena cava invasion. The long-term administration of phenoxybenzamine in PCC has not been reported in dogs.

Case presentation

A 14-year-old castrated male Poodle dog presented with an abdominal mass. On physical examination, hypertension, increased lens opacity, calcinosis cutis, generalized alopecia, and systolic murmur were observed. Serum chemistry and urinalysis profiles revealed hyperglycemia, hypercholesterolemia, elevated liver enzymes, and glucosuria. Abdominal ultrasonography showed a right adrenal mass with invasion of the caudal vena cava, which was cytologically diagnosed as suspected PCC. An adrenal mass (width × height × length, 28 × 26 × 48 mm³) was found on computed tomography and diagnosed as PCC with increased plasma metanephrines and normetanephrines. An adrenocorticotropin hormone stimulation test showed elevated adrenal hormones (androstenedione, estradiol, progesterone, and 17-OH progesterone) with normal cortisol, compatible with atypical Cushing’s syndrome. The dog was managed with trilostane, phenoxybenzamine, and insulin therapy. Glycosylated hemoglobin and fructosamine levels gradually decreased, and hypertension resolved. In the 10-month follow-up period, the liver enzymes levels gradually decreased, and the clinical signs of the dog were well-controlled without deterioration.

Conclusions

This case report describes long-term medical management without adrenalectomy of PCC complicated with atypical Cushing’s syndrome and DM.

Retrospective evaluation of canine heart base tumours treated with toceranib phosphate (Palladia): 2011-2018

Heart base tumours (HBT) occur commonly in older, brachycephalic dogs. A presumptive diagnosis is made based on location and appearance of the tumour via echocardiogram. Effective treatment options are limited to surgery (when feasible) or radiation therapy. Benefit of medical management is presently unknown. The goal of this retrospective study was to assess the efficacy and tolerability of toceranib phosphate for dogs with HBT. Twenty-eight dogs with histologically, cytologically confirmed or presumed HBT were evaluated retrospectively. Twenty-seven dogs were treated with single agent toceranib. One dog received combination therapy with concurrent metronomic chemotherapy. This dog was not included in response or survival analysis. Factors assessed included clinical signs, hematologic/biochemical parameters and response to treatment. For the 27 dogs receiving single agent toceranib, an overall response rate of 10% was found. Overall median survival time was 823 days (range, 68-1190 days). The overall response rate for the dogs presenting with metastasis was 28.5%, with a median survival time of 532 days (range, 77-679 days). This was not significantly different than the median survival time of 796 days for dogs who did not present with metastasis. Of the dogs displaying clinical signs at the time of diagnosis, 90% had improvement and 81% had complete resolution of signs after starting toceranib. Toxicity was seen in 54% of dogs with gastrointestinal distress as the most common toxicity but dose reductions were infrequent required. Results demonstrate that toceranib phosphate is a well-tolerated and effective treatment for inoperable canine heart base tumours including dogs with advanced or metastatic disease.