No pet parent ever wants to be told that their dog has cancer. It’s like being told that you’ll be saying goodbye forever to your pet real soon. For most individuals, the diagnosis of cancer is often the sign of the beginning of the end. And for those who simply love their hounds so much, it is almost unbearable to know that your pet is going to leave you soon. But the good news is that there are newer cancer treatment approaches that may offer the best hope for prolonging and improving the quality of life of dogs with cancer. One of them is chemotherapy. Here is everything you need to know about chemotherapy for dogs.

dog under the chemo therapy

Chemotherapy Explained

Chemotherapy is any drug or chemical substance that is specially formulated to kill cancer cells. They may have different mechanisms of action, but the end result is always the eradication of the cancer cells in dogs.

This is a lot similar to antimicrobial agents whereby specific chemicals are used to fight and kill specific microorganisms. As such, you can have antibacterial for those with bacterial infections, antiviral for those with viral infections, an antifungal for those with fungal infections, and so on. These chemical agents are specific to the type of microorganism that they need to neutralize.

While chemotherapeutic agents do not target germs or microorganisms in the body of the dog, they act in almost the same way by targeting cancer cells. This is where it can get tricky since no single chemotherapeutic agent can address all kinds or types of cancer cells. As such, veterinarians have to conduct a variety of tests to determine the type of cancer that the dog has. This is to make sure that the correct chemotherapy is used.

Now, even if the veterinarian is able to identify the type of cancer that the dog has, there is still a possibility that the chemotherapy given to the dog may not be effective. This can be due to a variety of reasons, but mostly due to possible resistance from the dog’s system. Therefore, whenever the dog is under chemotherapy, it is important that the vet keep a watchful eye on the progress of the chemotherapy sessions. There should be noticeable improvements in the dog’s symptoms and the continuing absence of side effects. If there will be side effects, these should only be minor ones and very minimal. Otherwise, if there is no improvement in the dog’s condition or there are a variety of serious side effects occurring because of the chemotherapy, the vet may have to make some modifications in the therapy. He may change the dose, increase or decrease the frequency, or even replace the chemotherapeutic agent with another one.

Is It Necessary?

One has to understand that chemotherapy works on a system-wide basis. This means that the chemotherapeutic agent is delivered through the blood to reach its target cancer cells. That being said, it is useful and absolutely necessary when cancer cells have already begun spreading from its site of origin. For example, if the dog has pulmonary adenocarcinoma there is a chance that the cells in this type of cancer can spread and reach the brain, heart, liver, bones, and spleen.

Because the cancer cells are already scattered throughout the different parts of the dog’s body, conventional cancer treatment like surgery and radiation therapy may no longer be as effective. This is where cancer chemotherapy can be very useful.

Cancer always starts in a single cell. Changes in the cell’s DNA can lead to the production of defective cells. Over the course of many years, these defective cells undergo a series of mutations that make them more and more different from the original normal cells. And each mutant cell can reproduce two daughter mutant cells. It is this collection of mutant cells that are detected as the cancer cell.

Unfortunately, early detection may not be readily possible because there are no presenting signs yet. You won’t see any sign on your dog that will tell you that it has cancer. That’s why it is important to have its DNA test so you’ll know if it has a genetic predisposition to certain types of cancer in dogs.

As the tumor grows, it breaks out from its initial site of growth. If the borders of this tumor growth are well-defined and haven’t reached the bloodstream or the lymph vessels yet, then the vet will usually recommend surgical removal of the tumor. However, if the tumor has already reached the lymphatics or the bloodstream or that its border is hardly distinguishable, surgery is not an effective solution. Chemotherapy is necessary since the cancer cells are already in the blood or are already in other parts of the dog’s body.

This is for solid tumors but if the cancer is in the blood or lymph such as lymphoma, chemotherapy is the treatment of choice. After all, you cannot perform surgery on blood, can you?

puppy under chemo

How Is Chemotherapy Administered to Dogs?

Depending on the type of agent used, chemotherapy can be administered either via injection or via the oral route. Injections are fast. You can bring your pet to the clinic, have it thoroughly evaluated by your vet including bloodwork, and have it receive its chemotherapy shot. After that, you can go home.

There are also chemotherapeutic agents that are very irritating when injected into the muscle or the subcutaneous tissue of the dog. As such, these may be administered via the intravenous route. This can take all day since the chemotherapeutic agent is often diluted in a bottle of IV fluid and then infused very slowly. However, this is quite uncommon in chemotherapy for dogs.

The oral administration of chemotherapeutic agents can be done either in the vet’s clinic or in the home. Usually, the first dose is administered at the veterinary clinic so that the vet will be able to demonstrate to the pet parent how to exactly administer the chemotherapy. Succeeding doses can then be administered at home.

As for the frequency of administration, this depends on the dog’s type of cancer, its overall health status, and the type of drug used as well as any wish the pet parents may have. Generally, chemotherapy is administered once a week, although there are some cases that can be administered once every 21 days. In such cases, the duration of the treatment can go on for 3 to 4 months before the dog is given its chemotherapy every 4 to 6 weeks.

The whole chemotherapy course can run for about 3 full months up to 3 years, depending on the type of cancer and the overall response of the dog to the treatment.

Are There Chemotherapy Side Effects I Should Be Concerned About?

There’s this notion that chemotherapy in dogs is as aggressive as chemotherapy in humans. After all, we’re still talking about cancer here. On the contrary, the chemotherapy treatments for dogs are less aggressive since their anatomy is different from ours. To put it simply, chemotherapy in dogs produces fewer and milder side effects than chemotherapy for humans.

The problem with chemotherapy is that it doesn’t only kill the cancer cell; it also kills the normal cell. This is why there are those who oppose chemotherapy because it adversely affects other cells that are not cancerous. You can call it collateral damage if you will.

The good news (well, for lack of better description) is that the killing of normal cells by chemotherapeutic agents in dogs can lead mostly to minor complaints such as diarrhea, vomiting, and loss of appetite. As a matter of fact, three-quarters to four-fifths of all dogs receiving chemotherapy will present without any side effects at all.

Sadly for those that do present with side effects, 3 to 4 percent will experience very severe vomiting and diarrhea which can lead to serious fluid and electrolyte problems. For these dogs, it’s imperative that they are brought immediately to an emergency veterinary facility so that fluid resuscitation can be initiated at once. The dog will also have to be on complete bed rest for about 3 to 5 days.

yorkie under chemo

Are There Precautions I Need To Observe?

Since the chemotherapeutic agent is present in the blood, it will take a few days before it can be completely flushed out from the dog’s system. As such, some of the drug metabolites can remain active in the dog’s fecal matter and urine. It is therefore important that you take precautionary measures when handling such excrements from your dog. You cannot use just any other glove to protect your hands when handling urine-soaked items or even picking up dog poop. Only chemo-proof gloves will suffice.

When administering oral chemotherapy to your dog, it is also important to wear the appropriate gloves as you don’t want any of the drug’s active ingredients to get onto your skin. It is also advisable to wash your hands after the administration of the oral chemotherapy even if you already wore gloves. The same is true when cleaning up your pet’s mess. Even though you wore gloves, it is still best to wash your hands thoroughly right after.

If you are pregnant or are breastfeeding your young baby, it is important to be especially cautious around your dog’s waste. The same is true for individuals with weakened or compromised immune systems such as elderly folks and individuals receiving steroids.

If you are going to store your dog’s chemotherapy drugs in the ref, make sure that it is well separated from medications for you and your family. This should help prevent accidental ingestion of the wrong medication. Should you accidentally ingest your dog’s chemotherapeutic drug, it is imperative to call your physician right away. Don’t call the vet as he does not have the legal right to give you medical advice, only veterinary advice.

How Much Does It Cost To Have My Dog Undergo Chemotherapy?

There are no standards when it comes to just how much you will be spending on the chemotherapy of your dog. This is largely dependent on the type of cancer that it has, the kind or type of drug to be used, the duration and frequency of the treatment, and the location of the veterinary clinic. Sometimes your location can also have an impact on the cost of chemotherapy.

For example, if an injection of chemotherapy costs about $50 to $60 per injection, you’ll be spending about $200 to $240 per month if it is a weekly therapy. If this needs to continue for the next 6 months, then the overall cost can be around $1,200 to $1,440. Some vet clinics charge more than others so it is important to keep this in mind.

canine under chemotherapy

Aside From Chemotherapy, How Else Can Cancer in Dogs Be Treated?

As we mentioned earlier, chemotherapy is just one of the treatment approaches to cancer in dogs. There are a few other treatment options that your veterinarian can lay down on the table.

We already mentioned surgery and that this approach is best for solid tumors that have very well-defined borders. It is also the treatment of choice when the cancer cells have not spread to other parts of the dog’s body yet, meaning it is still localized. In this procedure, the tumor is surgically removed from its site including the tissues in its immediate surroundings.

Another treatment option is radiation therapy. It is not a primary approach, however. Most vets will use radiation therapy as an adjuvant to help destroy cancer cells that may still remain after chemotherapy or surgery. This procedure requires the exposure of the dog to radiation so that cancer cells will be killed. Unfortunately, the radiation also affects normal cells that are hit by the radiation.

A newer treatment option is the use of immunomodulators in a process known as immunotherapy. This involves the introduction of a vaccine to stimulate the immune system of the dog to fight cancer cells.

Knowing your dog has cancer can be very devastating. However, knowing that chemotherapy can offer hope in improving the life of your dog that has cancer can somehow ease the burden of having to live with and care for such a dog.

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Olivia Williams
Olivia is our head of content for, mum of one and a true animal lover. With 12 different types of animal in her family, it's never a dull moment. When she isn't walking the dogs, feeding the cats or playing with her pet Parrot Charlie, you will find her product researching and keeping the site freshly updated with the latest products for your pets!


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