Hemangiosarcoma (HSA) is a highly malignant tumor arising from endothelial cells. These cells are derived from bone marrow precursors, classified as angiogenesis, inflammation or adipogenesis subtypes, and can develop lesions in any type of tissue containing vascular structures. HSA is a very common tumor in dogs representing 2-5% of all cancerous lesions and more than 50% of all splenic malignancies in the species. Although all breeds can be affected, male dogs from large breeds, such as German Shepherds, Golden Retrievers and Labrador Retrievers, particularly middle-aged to older dogs (~10 years-old), are more commonly affected.
HSA can develop in any tissue or structure of the body, with the most common sites being the spleen, heart, liver, skin and subcutaneous tissues. Visceral HSA is more common than dermal HSA and is associated with a poorer prognosis due the high rate of metastasis. Unfortunately, metastases commonly occur in the liver, omentum, and/or lungs, but they can occur anywhere throughout the body. Dogs with HSA have nonspecific clinical signs usually associated with primary tumor development and internal hemorrhage which is common with visceral lesions due to tumor rupture. These cases often present to a veterinary emergency service for marked lethargy or collapse, and emergency surgery may follow after identifying a hemoabdomen or mass on abdominal ultrasound.
Histopathologic examination is the standard method for definitive diagnosis. Just after diagnosis, clinical staging diagnostics are often performed to evaluate the extent of disease and appropriate treatment options. CBC, biochemistry, coagulation profiles, urinalysis, three-view thoracic radiographs, abdominal ultrasound and echocardiography are usually recommended.
The standard treatment for dogs with HSA is surgical removal of the primary lesion. Systemic therapy is usually recommended after surgery due to the high metastatic rate and aggressive nature of HSA. Doxorubicin is the most widely used chemotherapy agent for treatment of canine HSA. Doxorubicin may be used as a single agent or incorporated into a number of combinatorial protocols. Metronomic cyclophosphamide or chlorambucil with or without NSAIDs are also commonly considered systemic therapeutic options for canine HSA
Despite surgical and medical treatment options, the prognosis for visceral hemangiosarcoma remains poor. Surgical removal followed by systemic chemotherapy leads to a median survival time of 5-7 months with only about 10% of patients surviving to one year. More recent molecular data and therapeutic options may offer a potential improvement in patient survival or prognostic guidance by incorporating both tumor biology and behavior with genomic indications.
Sam Fisher, a 10-year-old male neutered Labrador Retriever, was presented to the Cornell University Veterinary Specialists in June 2019 due to sudden and marked lethargy. An abdominal ultrasound identified the presence of a hemoabdomen and Sam’s family elected to pursue emergency surgery. Surgery revealed a ruptured splenic mass which was surgically removed via splenectomy. Given the potential for neoplasia, a liver biopsy was performed from an adjacent liver lobe that was subjectively, grossly irregular in appearance. The entire spleen and liver biopsy were submitted for histopathologic evaluation. Histopathology of the splenic lesion was consistent with a diagnosis of hemangiosarcoma. Moderate anisocytosis and anisokaryosis was noted with multifocal necrosis and hemorrhage as well as a mitotic count of 6. The liver biopsy revealed mild hepatocellular vacuolar degeneration, but no evidence of neoplasia. Subsequently, Sam’s family was referred to a veterinary medical oncologist at The Veterinary Cancer Center for additional staging and treatment options.
On July 9, 2019, after discussion of available treatment options, Sam’s family elected to start metronomic therapy with cyclophosphamide (16 mg PO SID) and deramaxx (37.5 mg PO SID). In addition to chemotherapy, Sam’s family decided to pursue FidoCure® genomic diagnostics on the splenic tumor tissue.
The tumor tissue was sent for genomic (DNA) and transcriptomic (RNA) sequencing and in August 2019, the findings were reported. Genomic analysis revealed alterations of BRAF and N-RAS.
N-RAS is a single member of the RAS family of proteins involved primarily in regulating cell division. N-RAS belongs to a class of genes known as oncogenes that play important roles in cell division, cell differentiation and apoptosis. Activating N-RAS mutations lock the enzyme in an active state causing increased cellular proliferation via hyper-activating MAPK and PI3K signaling pathways.
Somatic mutations in the N-RAS gene are involved in the development of several types of cancer. The Q61R mutation, as in Sam’s case, has been widely investigated in many human cancers, such as: malignant melanoma, carcinomas, hematopoietic and lymphoid tumors . In dogs, the Q61R mutation has been identified in hemangiosarcoma, oral melanoma and oral acanthomatous ameloblastoma. In both species, this mutation is often associated with generalized therapeutic resistance, however ongoing trials are exploring the benefit of both upstream and downstream effector protein targeted inhibition.
BRAF is a gene which codes for the BRAF protein kinase which is part of the MAPK/ERK cellular signaling pathway. In humans, the aligned position (V168L) to Sam’s mutation (V105L), has been shown as a driver in lung cancer. This mutation leads to over phosphorylation of downstream proteins (MEK) which in turn can propagate unregulated cell growth and proliferation. Treatment with tyrosine kinase inhibitors (TKIs) that target MEK and BRAF have shown improved efficacy over traditional approaches in some human malignancies harboring these mutations.
Findings based on RNA (transcriptomic) expression profiling were consistent with overexpression of CDK4, JAK1, KDR, KIT, MEK1/2, and mTOR. CDK4 is the gene encoding cyclin dependent kinase 4. This family of proteins plays a critical role in cell cycle regulation, and dysregulation of this pathway has been identified as a driver for increased cell proliferation.
JAK1 is a gene that encodes a JAK1 protein member of a protein kinase family, activating and recruiting targets such as STAT proteins. The JAK-STAT pathway plays a role in cellular proliferation and tumorigenesis.
KDR is one of the subtypes of the family of vascular endothelial growth factor receptors (VEGFR). These receptors primarily bind a ligand called vascular endothelial growth factor (VEGF) leading to angiogenesis (the development of new blood vessels), stimulation and activation of PLC-gamma, and downstream signaling pathways such as PI3K/AKT. Upregulation of KDR and VEGF may lead to an increase in cell cycle progression and a therapeutic opportunity for drugs that inhibit angiogenesis.
KIT, or stem cell growth factor receptor, is a receptor tyrosine kinase involved in a number of cellular proliferation and growth processes. KIT activation results in increased intracellular signaling through several pathways including PI3K, MAPK and STAT, ultimately leading to cell proliferation and survival. c-KIT has been implicated in the pathogenesis of multiple human neoplastic diseases, and it’s mutations lead to a constitutively activated KIT product in the absence of ligand. Activating c-KIT mutations and aberrant KIT expression have also been described in canine cutaneous mast cell tumors. c-KIT mutations have been identified in the juxtamembrane domain, in exon 11, of canine MCTs and consist of internal tandem duplications and deletions in 30% to 50% of all intermediate- to high-grade mast cell tumors.
MEK is a gene that codes for the protein MEK1. This is a downstream protein that belongs to the MAPK/ERK signaling pathway. Overexpression of this gene may result in tumor cell growth, proliferation, and survival. Targeted inhibitors that prevent overactivity and dysregulated signaling of this protein may be successful approaches to treating MEK driven cancers.
MTOR encodes a serine-threonine kinase protein which is a downstream component of the PI3K cellular signaling pathway, a pathway important in regulating the cell cycle. The activity of mTOR has been implicated in human and canine cancer because of potentiating signals for neovascularization and cell growth. Upregulation of mTOR and the PI3K pathway promotes cell cycle progression and survival.
The FidoCure® Precision Medicine Report including genomic and transcriptomic analysis arrived on August 8, 2019, and indicated potential benefit from the incorporation of targeted therapy into Sam’s medical approach. After discussing the rationale of combinatorial approaches, the following targeted therapies were prescribed by Sam’s veterinary oncologist: • Imatinib 10 mg/kg/day (465 mg PO q 24 hours) • Rapamycin (mTOR inhibitor) 0.1 mg/kg/day (4.5 mg PO q 24 hours) Beginning in August 2019, these medications were administered orally by Sam’s family at home. Sam continued metronomic therapy (combination of cyclophosphamide and Deramaxx) until this treatment was discontinued in October 2019. Rapamycin was subsequently discontinued in November 2019 due to gastrointestinal side effects. Overt metastatic disease was not definitively diagnosed, although a restaging abdominal ultrasound in December 2019 did reveal two small nodules in the mesentery. Sam’s family elected to monitor these lesions via imaging and continue therapy with imatinib. Sam was able to tolerate therapy well and maintain a high quality of life until his passing in July 2020.
Sam retained a high quality of life for thirteen months after incorporating FidoCure® enabled diagnostics and treatment. By living over one year beyond diagnosis of this incredibly challenging cancer, Sam surpassed the commonly reported median survival time (5-7 months) for dogs with hemangiosarcoma treated with splenectomy and chemotherapy. Additionally, after incorporating FidoCure® enabled diagnostics and treatment, Sam and his family were able to have additional, quality time together.
“ With the FidoCure® treatment, we were able to not only control Sam’s cancer for some time but also do so with minimal side effects. Sam was able to enjoy a good quality of life for about a year which is longer than what is historically reported for those treated with injectable chemotherapy." — Dr. Dorothy Jackson Girimonte, DVM, DACVIM
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