Chemotherapy For Dogs

Written and verified by the lawyer Francisco María García

Last update: 22 December, 2022

Chemotherapy for dogs is usually used to treat lymphosarcoma and mastocytoma. Lymphosarcoma is a type of neoplasm that affects lymphocytes and can damage the liver and spleen.

On the other hand, mastocytoma is a type of skin cancer that affects mast cells — the connective tissues — and can spread to other organs. Also, the treatment has to be done as soon as possible.

In both cases, the chemical treatment’s effect is remarkable, with about an 80% success rate. However, chemotherapy can also be used to treat other cancers that are common in dogs. Below are some examples:

• Skin cancer
• Lymphomas
• Breast cancer
• Cancerous tumors (mainly in the head and neck)
• Testicular cancer
• Bone cancer

Do all dogs that are diagnosed with cancer need chemotherapy?

The answer is no because chemotherapy is one of the effective cancer treatments for dogs, but a vet is the one who decides if it’s necessary. Using it all will depend on the evolution of cancer in the body and the dog’s state of health. In general, the vet will recommend chemotherapy in the following cases:

• When the tumor affects several organs or expands in the body. This takes place when the cancer cells have spread throughout the body or are affecting several organs — for example, lymphoma — it becomes impossible to remove the tumor through surgery.

In these cases, chemotherapy is usually the best option to keep it from advancing and to extend the animal’s life expectancy. However, chemotherapy is not usually recommended if the cancer is already advanced, there’s metastasis, or the dog is very weak.

• When they don’t completely remove the tumor during surgery: in some cases, the extraction surgery is viable and effective, but the vet can’t remove the entire tumor.

In this case, the veterinarian can use chemotherapy after surgery to eliminate the cancer cells.

• When the tumor is too large to be removed by surgery: if the vet sees that the tumor is too large to be surgically removed, chemotherapy can be used to reduce its size.

Depending on the response to treatment, the vet will analyze the feasibility of post-chemotherapy surgery to remove the tumor.

• After removing a tumor: even when the surgery is successful and they remove the tumor, the vet may prescribe chemotherapy. This will eliminate any of the remaining cancer cells and help prevent the formation of any new tumors.

How does chemotherapy for dogs work?

Cancer cells have abnormal growth, meaning they multiply faster than normal cells. Chemotherapy is meant to slow down the growth and eliminate any cancer cells. Special drugs are used to detect the accelerated activity of the malignant cells and destroy them.

Chemotherapy is more effective for young or small tumors that show an intense rate of cell division.

With advanced cancer, cancer cells slow their reproduction down and enter a state of rest. In this case, chemotherapy drugs are unable to differentiate malignant cells from normal ones.

Are there any side effects of chemotherapy for dogs?

As with almost all drug treatments, chemotherapy has some side effects. However, it’s estimated that only 5% of patients experience negative results after treatment.

Among the main side effects of chemotherapy for dogs are:

• Food and digestive problems: lack of appetite, diarrhea, nausea, and vomiting. Fortunately, there are many medications and some natural supplements to prevent and alleviate these issues.
• Weakened immune system: some dogs may suffer a weakened immune system caused by the chemotherapy’s effect. This leaves them more vulnerable to developing numerous diseases, from the common cold to more complex infections.
• Hair loss: it’s rare for dogs to lose their hair during chemotherapy. However, some dogs may experience hair loss. Sometimes, the hair will grow with a different color and texture in those areas.

Fortunately, scientific advancements and veterinary medicine have made significant improvements in dog chemotherapy. Thanks to this, the prognosis for a cancer diagnosis is much more positive than in the past.