Chemotherapy in Dogs

Chemotherapy is a medical protocol used in dogs to target and destroy cancer cells growing in the body. The goal of chemotherapy is to prolong dogs’ survival after a cancer diagnosis through either remission or reducing the size of tumors in the body. Chemotherapy is often used in combination with surgery to treat various cancers in dogs. Depending on the cancer diagnosis, chemotherapy may be the primary method of treatment or it may be used in addition to surgery. A chemotherapy plan is most often drawn up by a veterinary oncologist and can be administered by a primary care veterinarian. 

Some chemotherapy is simply given in the form of a pill which your dog will ingest. This can either be given at home or by your veterinarian. For other forms of chemotherapy that are intravenously administered, your pet will need to visit your veterinarian. Your veterinarian will place a small catheter into your pet’s vein through which the chemotherapeutic agent will be delivered. Some chemotherapy agents need to be delivered slowly while others can be administered more rapidly. You can expect your dog’s chemotherapy session to last between 30 minutes and 2 hours. Depending on the type of cancer and chemotherapy protocol, your dog may need to return for more chemotherapy. Chemotherapy protocols range in span from a few weeks to several months.

The efficacy of chemotherapy is dependent on the type of chemotherapy and the goals of the owner and veterinarian and oncologist. Chemotherapy is most effective when a combination of different agents and, if warranted, surgery are used together. The effects of chemotherapy are permanent on those cancer cells that it has damaged. In some cases, the dog has an aggressive or advanced cancer and the goal of chemotherapy is not for remission but palliative. Treatments related to chemotherapy include surgical resection and radiation therapy. Surgical resection alone serves to debulk any large tumors, however, microscopic disease may remain behind. Radiation therapy targets cancer cells but is not effective alone for large tumors in dogs. The most effective cancer treatment often involves a combination of several techniques as they all have their strengths and weaknesses.

Chemotherapy is a non-invasive procedure so your dog will be in and out of the veterinarian’s office the same day. Recovery from chemotherapy involves the management of side effects of the chemotherapeutic agents. Most commonly seen side effects are nausea, vomiting, and diarrhea. Your veterinarian will give your dog anti-nausea medication if they exhibit these side effects. Chemotherapy can also lower your dog’s white blood cell count so your dog will have white blood cell counts taken at subsequent chemotherapy visits. Some chemotherapeutic agents can affect your dog’s liver or kidneys. If one of those agents is being used, your veterinarian will order liver or kidney blood work to ensure that they remain healthy during the course of chemotherapy. 

The cost of chemotherapy varies with the treatment protocol and size of your dog. The range varies from $500 to $8,000 including bloodwork and follow-up staging tests. Your veterinarian will work with you to determine an estimate based on your dog’s particular cancer. The lower price point includes the price for diagnosis plus a prednisone only protocol. This protocol is used for lymphoma as a palliative option. The high price point would include a combination of several therapies including surgical excision and radiation therapy over the span of several weeks in addition to chemotherapy. 

Factors to take into account when considering chemotherapy are costs associated with treatment, quality of life for your dog and expected survival time with chemotherapy. Benefits of chemotherapy include elongation of survival time with cancer. Risks of chemotherapy include damage to kidney, liver and bone marrow due to the mechanism of action of certain chemotherapeutic agents. Potential of cancer recurrence depends on the chemotherapy protocol chosen as well as the type of cancer. For example, osteosarcoma (bone cancer) has a high rate of metastasis even with surgery and chemotherapy used in combination. However, certain other tumors such as mast cell tumors can be cured with surgical resection and chemotherapy.

Dogs can contract a wide variety of cancers throughout their lifetime. Preventing cancer is unfortunately very difficult to do. It is difficult to pinpoint exactly which external and internal factors play a role in cancer development in dogs. Some dogs are predisposed to developing certain cancers based on their breed. Many dogs develop cancer as they advance in age. Though preventing cancer is difficult, there are certain cancers that can be prevented with surgery. For example, mammary tumors, common to female dogs, can be prevented by spaying your dog before her first heat cycle. Testicular tumors can be prevented by having your dog neutered. 

Keeping your dog in good health in general will help if cancer is suspected, as they will be better candidates for surgery, chemotherapy, and all other necessary treatments. Taking your dog in for regular veterinary visits throughout their life will achieve the goal of keeping them in good health and will help ensure that if cancer does form, it is discovered early.