Chemotherapy Options for Cancer in Dogs

What is Chemotherapy?

Chemotherapy uses drugs to target rapidly growing and dividing cells. This means the medication can attack cancer, but it also attacks normal and healthy rapidly dividing cells in the body which can lead to side effects. We’ll discuss this more soon.

Chemotherapy is available in injectable and oral forms and there are often multiple drugs used initially or when/if cancer comes back. Injectable chemotherapy is administered at the vet clinic and often is given in under an hour. A few options need to be given much slower and may take part of the day to complete the treatments. These injections are often repeated weekly or every few weeks, depending on the type of cancer being treated and the protocol being used.

Oral chemotherapy pills are available to treat some forms of cancer. This is a nice option since your pet can be given the medication at home and only needs to go into the clinic every few weeks or so for progress exams and blood work monitoring. Your vet can send home special gloves to wear when handling and administering the pills to your dog to reduce your exposure risk.

Chemotherapy treatment durations can vary. It all depends on the type of cancer being treated, the exact chemo protocol being used, and how well your dog responds to treatment.

How do I know if my dog’s cancer will respond to chemotherapy?

Chemotherapy is typically used on cancers that have already spread (no longer a single tumor) or if the dog has other health issues and is not a good candidate for surgical removal of the primary tumor.

Blood tests, cytology, flow cytometry, and biopsies are common tests needed to diagnose the form of cancer present and determine how aggressive it is. Not all forms of cancer respond to chemotherapy and not all chemo drugs treat the same types of cancer, so you need a diagnosis before starting treatment. Once your pet has been diagnosed with cancer, radiographs of the chest and abdomen, MRI, or ultrasound testing is often performed to see if cancer has spread and help grade the cancer. Cancers caught early that are low grade tend to respond the best to treatment.

Side Effects of Chemotherapy Treatment for Dogs

Dogs are typically given a lower dose than humans for cancer treatment, so the side effects are often mild in comparison. Many dogs have absolutely no side effects. Since chemo drugs attack rapidly dividing cells, the cells in the GI tract and bone marrow are often affected also. This means your dog can develop low red and white blood cells counts, leading to lethargy and an increased risk of infections. They may also have a reduced appetite or vomiting and diarrhea that may last a few days after treatment.

Regular blood testing is needed for dogs undergoing chemotherapy to assess their red and white cell counts. If the white cells drop too low, an antibiotic may be started to reduce the risk of infection and the next treatment may be delayed or the treatment plan may be adjusted to allow the red and white blood cells to return to normal levels.

Luckily, there are medications to help reduce nausea, improve appetite, and control diarrhea in dogs going through chemo treatment. Most of the side effects related to the GI tract only last 2-3 days post-treatment.

Dogs rarely lose their hair during chemo treatment. They may lose their whiskers. Some breeds, like Poodles and Yorkies, may lose their hair, but it should grow back after the treatment is completed. Sometimes the hair grows back in a different color.

My vet doesn’t administer chemotherapy. Are there chemotherapy alternatives for my dog?

Not all vets administer chemotherapy at their clinics. There are a lot of safety issues, drug dosing variations, and other concerns. Luckily, there are veterinary specialists for oncology and they have all the latest information, drug safety handling equipment, specially trained technicians, and more to help give your dog the needed treatments. Be sure to discuss referral to a veterinary oncologist with your regular vet.

Surgical removal of a single tumor is often the treatment of choice and can be curative in many cases. Chemotherapy is typically used for cancers that have already spread, for tumors in locations that cannot be removed surgically, or for patients that cannot handle the anesthesia needed for surgical removal.

Radiation therapy may also be used to help treat your dog’s cancer. This involves directing a beam of radiation directly at the cancer site itself and requires anesthesia for each treatment.

Immunomodulation therapies are available for a few specific types of cancer, like bone cancer. These treatments direct the dog’s own immune system to attack the cancer cells.

Read more:

Warning Signs of Cancer in Dogs

Stomach Cancer in Dogs and Cats

Intestinal Cancer in Dogs and Cats

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