Sarcomas can be an aggressive type of cancer in dogs. They are often very difficult to treat with conventional treatments such as surgery and radiation therapy.
If soft-tissue sarcoma is high-grade, the tumor can recur and spread even after a dog receives today's standard-of-care treatments.
The good news?
With the help of new immunotherapy treatments, it may be possible to reverse or prevent the recurrence of soft tissue sarcoma.
This article provides an introduction to canine soft tissue sarcoma and describes both conventional and new treatment options. Clinical trials enrolling patients with STS are also described.
What's Canine Soft Tissue Sarcoma?
Soft Tissue Sarcomas (STS) are solid tumors that develop in soft tissues, such as muscles, fat, and other connective tissues.
They are a diverse group of tumors that include fibrosarcoma, peripheral nerve sheath tumors, myxosarcoma, leiomyosarcoma, liposarcoma, rhabdomyosarcoma, leiomyosarcoma, synovial cell sarcoma, and lymphangiosarcoma.
A relatively rare form of cancer for people, sarcoma accounts for only 1% of adult cancers in human patients.
However, the statistics for our canine companions are much more concerning – sarcomas (including STS) are roughly 15 times more common in dogs than humans.
These tumors can arise in various locations and this table describes different types of sarcoma and common locations. (Note that osteosarcoma and chondrosarcoma are bone cancer and not STS. Hemangiosarcoma is described in more detail in a separate article)
What are the signs and symptoms?
Signs of soft tissue sarcoma in dogs may include one or more of the following:
A Lump or Mass: The most common symptom of soft tissue sarcoma is the presence of a lump or mass under the skin. This lump may be painless and can grow over time.
Pain or Discomfort: Depending on the size and location of the tumor, it may cause pain, tenderness, or discomfort. The pain might not be severe and can be mistaken for other conditions.
Limited Mobility: If the tumor is located near a joint or muscle, it can limit the range of motion and cause difficulty in movement.
Swelling: Soft tissue sarcomas can cause localized swelling in the affected area. The swelling might not be immediately obvious but can become more noticeable as the tumor grows.
Nerve Compression Symptoms: If the tumor presses against nerves, it can lead to symptoms like weakness or even loss of function in the affected area.
Fatigue and Weakness: In some cases, especially if the tumor is large or advanced, it can cause a general feeling of fatigue and weakness.
Gastrointestinal Symptoms: If a tumor develops in the abdominal area, it could cause symptoms like abdominal pain, nausea, vomiting, or changes in bowel habits.Soft tissue sarcoma
How is soft tissue sarcoma diagnosed?
Soft tissue sarcoma in dogs is usually diagnosed by fine needle aspiration or biopsy.
With Fine Needle Aspiration (FNA), a small needle is used to extract some cells that are examined under a microscope.
If testing from an FNA is inconclusive, your vet may recommend a biopsy where a piece of the tumor is removed. A biopsy can usually reveal much more about the tumor such as its grade than with FNA.
Companies such as Vidium Animal Health and Fidocure offer genomic testing of biopsied tumor samples. Their reports can be used by a vet to guide the choice of targeted therapy for the patient (see below).
Depending on the location of the tumor, additional testing such as ultrasound, x-ray imaging, and CT scans might be used.
What are the treatment options for canine soft tissue sarcoma?
The choice of treatment depends on the tumor's location, type, size and grade, as well as the age and overall health of the dog. Here are the main treatment options:
Surgery: Surgery is the primary option for most patients. The goal of surgery is to completely remove the tumor with adequate margins of 2-3 cm beyond the extensions of the mass. If any cancer cells remain (because only narrow margins or dirty margins could be attained with surgery), cancer has not been removed, and there will be a risk of recurrence. If the tumor is localized and the surgical margins are wide and clean, a dog may have an excellent prognosis.
Radiation Therapy: Radiation therapy is often used after surgery to kill any remaining cancer cells that couldn't be removed by surgery alone. Radiation therapy can also be used as the main treatment for tumors that cannot be easily removed surgically or for dogs that are not surgical candidates. The treatment may last several weeks, with the patient getting radiation therapy Monday - Friday, five days a week.
Chemotherapy: Chemotherapy may also be used if cancer could not be completely removed by surgery or a dog is not a surgical candidate.
Targeted Therapies: Targeted therapy drugs specifically target certain molecules or pathways involved in cancer growth. Tumor samples are tested to determine the types of mutation that can be targeted.
Immunotherapy: Immunotherapy harnesses the dog's natural immune system to target and attack cancer cells. It can involve vaccines, immune-stimulating drugs, or other therapies that enhance the immune response against the tumor. See below for more details.
Palliative Care: In cases where the tumor cannot be completely removed or cancer has spread, palliative care focuses on managing symptoms and improving the dog's quality of life. This might involve pain management, dietary adjustments, and supportive therapies.
Targeted therapy drugs, unlike chemotherapy drugs, are designed to be highly specific, focusing on particular molecules or pathways that are often overactive in cancer cells. This specificity aims to minimize damage to healthy cells so that the side effects are minimized.
They may be helpful in inhibiting signaling pathways, preventing blood vessel growth (angiogenesis) or in blocking specific receptors.
To determine which drug(s) might best help the patient, a tumor sample must be analyzed for genomic mutations.
A company that offers genomic testing is Vidium Animal Health.
Genomic testing will yield a report that can guide your veterinarian choose a drug that might help stabilize or shrink the tumor.
For example, in a case study reported by Vidium Animal Health, a 14-year-old female Yorkshire Terrier had twice recurrent soft tissue sarcoma in her muscle. With the help of a targeted therapy drug imatinib, the patient survived extra 5 months.
Another company Fidocure also offers genomic testing of tumor samples and offers targeted therapy drugs.
Because of the heterogeneity of cancer cells and their ability to mutate in response to therapy, resistance to targeted therapy can develop over time.
In contrast to chemotherapy and targeted therapy, immunotherapy works by training the dog's own immune system to attack and destroy cancer cells.
Some of the potential benefits of immunotherapy treatments or enrolling in a clinical trial include:
the clinical study might cover and pay for surgery and advanced treatments
less side effects
stopping recurrence and metastasis
offers another option if standard-of-care treatments do not work
Today's cancer immunotherapy does not help every patient, however. The patient response depends on many factors. Researchers are still trying to figure out why some patients respond spectacularly well and become cured while other patients do not respond.
Please ask your veterinarian if any of the following treatments might be suitable for your pup.
Location: Anywhere in North America
What is it? A drug that stimulates the immune system to attack cancer cells. The active ingredients consist of non-pathogenic bacterial cell wall fraction and nucleic acid. If the patient cannot receive surgery or if the cancer cannot be completely removed, Immunocidin may help prevent recurrence or metastasis. Intra-tumoral injection and/or IV infusion.
Data: None for STS. Small study results have been published for other types of cancer (osteosarcoma, bladder cancer, mammary tumors). The safety of this drug has been published in many studies including with canine patients and human patients.
Contact: (613) 308-9788 or info@NovaVive.ca
Anything else? Immunocidin is fully approved by the USDA for mammary tumors. Multiple pilot studies are underway to evaluate the efficacy of this bacterial therapy to help dogs with different types of cancer including osteosarcoma, transitional cell carcinoma, soft tissue sarcoma, lymphoma, and hemangiosarcoma.
Contact Novavive and speak with Dr. Miriam Cervantes if you'd like to learn about Immunocidin and soft tissue sarcoma (Partially supported by CCA)
More information: https://www.novavive.ca/canine-research
Yale Canine Cancer EGFR/HER2 Vaccine
UPDATE: This trial is no longer accepting patients with STS. But this may change in the near future if the vaccine receives conditional approval from the USDA.
Where? Multiple clinics in the US and one clinic in Canada. More information can be found on this page: https://www.ccralliance.org/yale-status
What is it? A peptide vaccine that trains the dog's own natural immune system to target tumor cells that are overexpressing EGFR and HER2 proteins. (Funded by Canine Cancer Alliance i.e. CCA)
Contact: Mark Mamula, email@example.com
More information: https://www.ccralliance.org/yale-status
What is it? A vaccine created from the dog's tumor cells trains the immune system to target and kill tumor cells. Also called "Autologous Vaccine". Requires coordination before sending in tumor sample. Three injections over 3 weeks. Approximately $1500.
Data: Safety studies have been published. No data specifically for STS. Some efficacy data has been published for hemangiosarcoma.
Contact: 860-519-9956 or https://www.torigen.com/contact-us
Location: Anywhere in the US. Make sure to contact them before surgery.
More information: https://www.torigen.com/
IL-12 Based Immunotherapy
Location: Columbia, Missouri
University of Missouri
What is it? Canine patients receive a drug that stimulates sustained production of anti-tumor cytokine IL-12. The goal is to increase T cells (anti-tumor immune cells) in the tumor microenvironment and to create an immune memory to prevent sarcoma recurrence. Dogs with high-grade soft tissue sarcoma are enrolled. The study pays for the surgery and immunotherapy to qualified patients. (Originally supported by CCA)
Data: Mouse model studies have been published.
Contact: Sydney Miget, firstname.lastname@example.org
Other Clinical Trials
The following are additional clinical trials enrolling patients with soft tissue sarcoma in different locations.
Histotripsy (Ultrasound) Treatment for dogs with STS
Location: Roanoke, Virginia
Virginia Tech Animal Cancer Care and Research Center
What is it? Histotripsy treatment is a non-surgical, non-radiation, non-thermal focused ultrasound treatment to kill soft tissue sarcomas affecting pet dogs. This technology has also been used in human patients with liver tumors. Histotripsy focuses microsecond-long soundwaves through the skin onto a precise target area of the tumor. This causes air bubbles in the tumor tissue to expand and collapse, mechanically disintegrating the surrounding tumor tissue. Research studies in rodents, pet dogs, and humans have shown that the liquified tissue stimulates the immune system to recognize cancer in other parts of the body.
Data: None yet
Contact: Shawna Klahnm, email@example.com
STING Agonist Immunotherapy
Location: Philadelphia, Pennsylvania
University of Pennsylvania
What is it? STING agonist compound can promote strong anti-tumor immune system response. This study is enrolling dogs that weigh 33lbs or more with high-grade soft tissue sarcoma, as well as malignant melanoma, mammary carcinoma, squamous cell carcinoma on the head or neck.
Data: None yet
Contact: June Chiango, firstname.lastname@example.org
More information: https://www.vet.upenn.edu/veterinary-hospitals/ryan-veterinary-hospital/services/comprehensive-cancer-care/cancer-care-clinical-trials/cancer-care-clinical-trials/immunotherapy-clinical-trial-for-dogs-with-solid-tumors
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Questions? Email us at info@ccralliance and we'll get back to you as soon as we can!
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All information provided by the Canine Cancer Alliance website is for informational purposes only. It is not intended to be a substitute for professional veterinary advice.
Always seek guidance from your veterinarian with any questions regarding your pet’s health and medical condition.