Chemotherapy in Dogs

Chemotherapy is a good treatment alongside some tumor surgeries, as well as a standalone treatment in many others. Cancer isn't just affecting more and more humans — it's also affecting our furry friends.

Faced with this diagnosis, it's normal to feel confused and start having many questions. That's why, at Soyunperro, we'll answer the most common questions related to cancer in dogs and chemotherapy.

What Is Chemotherapy?

It can be defined as the use of cytostatic drugs (which halt rapid cell growth) in the animal with the goal of keeping tumor growth under control (preventing metastasis, shrinking the mass, making it disappear…), trying to maintain the animal's quality of life and survival this way.

When Is It Recommended to Give Chemotherapy to a Dog?

As mentioned above, chemotherapy is used to treat some tumors, since the pillars of cancer treatment are surgery, chemotherapy, and radiotherapy. Generally, the best option is surgery whenever feasible, but considering the dog's age, ability to recover, and quality of life, we need to choose one, the other, or a combination of several treatments.

To know whether a dog's cancer is treatable through chemotherapy, exams and/or additional tests need to be done first to determine where the tumor is located, its size, its stage of development, as well as the factors described in the previous paragraph.

Chemotherapy is advisable in certain cases:

1. When there's no option to operate on the dog or the tumors can't be removed with all margins through surgery.
2. If there's risk of metastasis to nearby organs, or metastasis is already present and we want to try to extend life as much as possible while maintaining quality of life.
3. After removing the tumor, to eliminate as many remaining malignant cells as possible left in the dog's body.

How Does Chemotherapy Work?

Cancer usually spreads quickly throughout the whole body, since cancer cells divide faster than the rest (high mitotic rate). To reduce or slow this process, chemotherapy is used.

These antineoplastic drugs penetrate target cells through diffusion. Once inside the cell, their points of action are the DNA, enzymes, membranes, and microtubules. This dose is calculated based on the patient's body surface area (m²), and sometimes based on weight (kg).

However, it has side effects, since normal cells are affected too, given that they go through the same cell cycle as cancer cells (though not at the same speed). So, the cell populations most often affected are:

1. Bone marrow
2. Gastrointestinal epithelium
3. Hair follicles.

The dose and frequency of sessions, as well as the type of chemotherapy, should always be determined by a veterinary professional after evaluating the dog's particular case. Chemotherapy is normally given orally or intravenously.

Effects of Chemotherapy on Our Dog

Something you should keep very much in mind is that chemotherapy in dogs can have side effects depending on the drug used, as well as its route of administration. In some cases, after several doses of a drug, thrombocytopenia (low platelet count) can occur. In this situation, stopping the drug is warranted due to the risk of bleeding.

Common side effects are:

• Cushing's syndrome
• Bone marrow toxicity
• Neutropenia (decreased neutrophil white blood cells).
• Anemia

You should also contact the vet for any behavioral change.

Tips for Dealing With Canine Chemotherapy

Our goal throughout the entire treatment should be offering our pet the best possible quality of life. Despite the many possible side effects that chemotherapy may seem to have at first glance, it's fairly well studied and advanced nowadays, offering a wide range of medication options.

A positive attitude toward the situation can help our pet, since all our emotions are transmitted to them. So it's important to make sure your furry friend feels happy and loved despite its illness. It's also important for it to have a comfortable place to rest without getting stressed.

So I encourage you to try this type of therapy whenever the vet considers it appropriate, since in certain cases it's better to try than to think about what would have happened if we hadn't. In case the dog's condition ends up deteriorating too much, it's possible a tough decision will need to be made about whether it's necessary to euthanize our dog (something only a vet should propose).