Canine Sarcoma: The Journey from Diagnosis to Recovery

(Go HERE to read about "Unraveling the Link Between Diet and Tumor Growth")

A relatively rare form of cancer for humans, sarcoma accounts for only 1% of adult cancers. The stats for our canine companions, however, are much more concerning – sarcoma is roughly 15 times more common in dogs than humans.

Even more concerning is that sarcoma in dogs tends to be aggressive and difficult to treat with today's conventional therapies.

The good news? Long-term survival may become possible with the help of new treatments such as cancer immunotherapy, a main focus of the research supported by the Canine Cancer Alliance (CCA).

What is Sarcoma?

• Sarcomas are solid tumors that develop from various types of connective tissues.

• Common sarcoma types for dogs include osteosarcoma, hemangiosarcoma, and soft tissue sarcoma (STS).

• Osteosarcoma is a bone tumor that develops from the cells responsible for bone formation.

• Hemangiosarcoma is a cancer that originates from the cells lining blood vessels.

• Soft-tissue sarcomas include a range of tumors that develop in muscles, fat, and other soft tissues.

Molly's osteosarcoma spread to her lungs even after surgery and chemo. But with a new immunotherapy treatment discovered by Prof Steven Dow and his team at Colorado State University, her tumors disappeared. (Photo Source: University of Colorado, School of Medicine)

Signs & Symptoms

Sarcoma can grow from tissues that connect and support the body, including bone, muscle, fat, tendons, ligaments, lymph and blood vessels, and nerves.

Osteosarcoma is the most common type of bone cancer, often affecting the long bones of the limbs with symptoms including lameness, swelling, and pain. It tends to be highly aggressive and has a strong propensity for spreading (metastasis), commonly spreading to the lungs.

Hemangiosarcoma starts in the blood linings and predominantly affects the spleen, liver, and heart in dogs. Symptoms include a swollen belly (abdominal distension), weakness, and pale gums due to internal bleeding.

Soft Tissue Sarcoma (STS) includes a diverse group of tumors such as fibrosarcoma, peripheral nerve sheath tumor, leiomyosarcoma, liposarcoma, and histiocytic sarcoma, among others. These tumors can arise in various locations throughout the body and may present as a softer mass or localized swelling.

Signs and symptoms?

Different sarcoma types and primary locations

How is it diagnosed?

Diagnosis of canine sarcoma involves a combination of physical examination, imaging (ultrasound, X-ray, CT scans, MRI), tissue sampling, and histopathological analysis.

X-rays, CT scans, or ultrasound imaging may be used to evaluate the visual characteristic and extent of the tumor and identify any metastatic spread.

Tissue sampling, typically through a biopsy or fine-needle aspiration, is crucial for obtaining a definitive diagnosis and determining the specific sarcoma subtype.

The collected samples are then examined under a microscope by a veterinary pathologist to assess the tumor's characteristics, grade, and stage. This information helps guide treatment decisions and prognosis.

What are the standard-of-care treatments and the prognosis for dogs with sarcoma?

The conventional treatment options for canine sarcomas often involve several approaches including surgery, chemotherapy, and radiation therapy.

In the case of osteosarcoma, the primary treatment is surgery, coupled with chemotherapy to slow metastases.

Osteosarcoma has a relatively guarded prognosis as it is very aggressive and has a high metastatic potential. The median survival time ranges from several months to a year with conventional treatments. You can read a detailed account of a pup diagnosed with osteosarcoma here.

Hemangiosarcoma, especially when affecting the spleen, typically requires surgical removal of the tumor and chemotherapy. Hemangiosarcoma carries a poor prognosis due to its highly malignant nature and the potential for rapid spread. Even with treatment, the prognosis is generally guarded, and the average survival time ranges from a few months to a year.

Soft tissue sarcomas are usually managed with surgery, followed by radiation therapy or chemotherapy to address any remaining cancer cells. See here to learn more about conventional treatment options for soft tissue sarcoma.

The prognosis for canine patients with STS depends on the subtype and location. Some low-grade soft tissue sarcomas can be effectively treated with surgery, resulting in a good prognosis. However, high-grade soft tissue sarcomas or those located in challenging areas may have a more guarded prognosis, with elevated potential for recurring or metastasis.

Are certain dog breeds more prone to developing sarcomas?

Yes, certain dog breeds have a higher predisposition to developing specific types of sarcomas.

For example, large and giant breeds, such as Great Danes, Bernese Mountain Dogs, and Saint Bernards, have an increased risk of developing osteosarcoma. Greyhounds also have a higher incidence of osteosarcoma. Hemangiosarcoma, osteosarcoma and soft tissue sarcoma are more common for golden retrievers.

Eight year old golden Kinako was treated by surgery and radiation therapy for fibrosarcoma, a form of soft tissue sarcoma. The treatment helped slow metastasis but the cancer returned a year later.

It's important to note that sarcomas can affect dogs of any breed or mixed breeds, and genetic predisposition is not the sole determining factor in their development.

Can canine sarcoma be prevented?

Unfortunately, it is impossible to prevent the development of sarcomas in dogs with absolute certainty.

Some environmental factors and genetic predispositions may contribute to the risk, but the exact causes are not fully understood. General measures to promote overall health, such as providing a balanced diet, regular exercise, routine veterinary care, and avoiding exposure to known carcinogens, can help maintain a dog's well-being.

If you suspect your dog may have issues, coordinate a veterinary exam as soon as possible. Early detection through regular check-ups and prompt evaluation of abnormal signs or masses can facilitate timely diagnosis and treatment, potentially improving the outcome.

What are the new advances in treating canine sarcoma?

Targeted Therapy is a form of chemotherapy but the drugs specifically target key cancer pathways.

New companies such as Vidium Animal Health and Fidocure offer services to analyze tumor genetic mutations and identify the drugs that target specific genes and proteins that drive cancer cell growth. Because of the heterogeneity of cancer cells and their ability to mutate dynamically, resistance to targeted therapy can develop over time. Very little data has been published on the efficacy of targeted therapy for osteosarcoma, hemangiosarcoma, soft tissue sarcoma and other types of sarcoma.

Immunotherapy Treatments, including therapeutic vaccines, are promising options for dogs with different forms of sarcoma. By recreating the dog's natural immune system to target tumor cells, immunotherapy can put some patients into a longer-term remission and avoid metastasis.

For example, studies have shown that therapeutic vaccines such as HER2/neu targeting Listeria based vaccine developed at the University of Pennsylvania and the EGFR/HER2 vaccine from Yale School of Medicine have helped stop metastasis and allowed some patients to enjoy long survival not usually possible with conventional therapies.

Maggie had her leg amputated after osteosarcoma diagnosis. EGFR/HER2 vaccine helped prevent lung metastasis and cancer recurrence. She is still cancer-free three years post diagnosis.

In one of CCA’s most promising studies, many dogs were able to avoid cancer recurrence and several dogs with metastatic osteosarcoma became cancer-free with the help of the EGFR/HER2 vaccine. You can learn about the status of this study here.

One lucky dog is Maggie. She had her leg amputated after an osteosarcoma diagnosis. She received the EGFR/HER2 vaccine, which helped prevent lung metastasis so common for dogs with bone cancer. She is still cancer-free three years post-diagnosis.

A different study (funded by NIH) is also uncovering how oral drugs can be added to create an anti-cancer immune environment. Molly's osteosarcoma spread to her lungs even after surgery and chemo. But with new immunotherapy developed by Professor Steven Dow and his team at Colorado State University, her tumors disappeared and she was back enjoying hikes in the beautiful mountains of Colorado.

This blog post is one in a series of four being published during July, which is National Sarcoma and Bone Cancer Awareness Month.

In future posts, we will cover immunotherapy more in-depth, including how it works, its risks and limitations, and strategies for improving its efficacy.

Questions? Please contact info@ccralliance.org, and someone from the CCA team will reply to your message as soon as possible.