Chemotherapy Uses in Non-Cancer Cases in Pets

Medical articles

Chemotherapy and other immune-suppressive drugs aren’t only used in cases of cancer in pets. Sometimes, these same drugs provide targeted treatment for other medical conditions in dogs and cats.

“We use forms of immune suppressive therapy for autoimmune diseases,” says Rodney Page, DVM, director of Colorado State University’s Flint Animal Cancer Center, who is board-certified in both internal medicine and oncology. “Those can be traditional chemotherapeutic agents that have been tested and are approved for different types of cancers, but they have also been useful in suppressing the immune system to allow symptoms of autoimmune diseases to be reduced.”

Pets can suffer from autoimmune conditions affecting many areas of the body, including:

  • Central nervous system

  • Skin

  • Kidneys

  • Joints

  • Gastrointestinal tract

  • White or red blood cells

Page explains that there is also a lupus-like syndrome in dogs, where symptoms act like many other diseases.

So, which drugs in particular might your veterinarian recommend in non-cancer cases?

Steroids for Many Things

Yes, steroids such as prednisone or dexamethasone.

Jennifer Locke, DVM, a board-certified veterinary oncologist at Southeast Veterinary Oncology and Internal Medicine in Orange Park, Florida, says, “When we are looking at any of the steroids, they cross the line between chemotherapy and anti-inflammatory therapy. So, yes, you could consider any of the steroid classes as something that would fall under the chemotherapy category.”

In dogs and cats, steroids are used in countless kinds of non-cancer cases. At some point in your pet’s life, he’ll likely need steroids, probably short term, for something.

Methotrexate for Arthritis (also called Rheumatrex, Trexall)

As with people, the chemotherapy drug methotrexate is sometimes used to treat some forms of arthritis in pets.

Cytarabine for Neurologic Conditions (also called cytosine arabinoside or cytosar)

“Cytarabine is used for neurologic diseases because it’s one of those rare drugs that crosses the blood-brain barrier,” Locke explains.

It is used in inflammatory neurologic diseases. For example, my Border Collie, Lilly, receives four subcutaneous cytarabine injections over two days every three weeks for her vaccine-induced meningoencephalomyelitis, which has turned into a full-blown autoimmune condition (likely terminal) affecting her brain and spinal cord.

CCNU for Neurologic Conditions (also called Lomustine or CeeNU)

This is another chemo drug that crosses the blood-brain barrier and is sometimes used in pet neurologic cases.

“This is one we can use for refractory situations for neurologic autoimmune conditions,” Locke says. “It ends up being the ‘clean-up crew’ for neurologic disease as far as having a slightly bigger gun push.”

Refractory essentially means the disease hasn’t responded to traditional treatment, doesn’t improve as expected, or flares up regularly. GME (granulomatous meningoencephalomyelitis) is an example of a disease that might require CCNU.

Vincristine for Low Platelet Counts Causing Bleeding (also called Oncovin, Vincasar PFS, Vincrex, vincristine sulfate, VCR)

“Vincristine is one of the cornerstone drugs for lymphoma in people and animals,” Locke explains. “We find that vincristine actually has this really specific function of being able to promote platelet maturation and release from the bone marrow. When we have dogs with autoimmune hemolytic anemia (IMHA) or thrombocytopenia, when their platelet levels drop really low, one of the things we do is give vincristine to try not only to suppress the immune system but also to promote the maturation and release of platelets. We use this especially for dogs whose counts have dropped so low that they are having spontaneous bleeding.”

Chlorambucil for Inflammatory Bowel Disease (also called Leukeran)

Veterinarians often use this pill form of chemotherapy – along with the steroid prednisone – to treat inflammatory bowel disease (IBD) in dogs and cats.

“IBD is a huge issue, especially in older cats,” Locke says. “We see a lot of IBD as cats get older, and a lot of oncologists believe there is a continuum of IBD, which is usually a very lymphocytic inflammatory condition. It probably then transforms into low-grade lymphoma.”