Is Dog Chemotherapy Worth It?

Chemo for Dogs is Worth Considering

A common concern for dog lovers is whether or not chemotherapy will make their dog feel sick. You may have previous experiences with chemotherapy administered to humans with cancer and may be hesitant to make this choice for your dog.

Less aggressive doses of chemotherapy are utilized in animals to minimize adverse side effects. Although chemotherapy in animals is typically not curative, when used appropriately, it can improve the quality and quantity of life for the dog being treated.

Lymphoma, for example, is a common cancer in dogs, and it is particularly susceptible to chemotherapy. The mean survival time of a dog with lymphoma without treatment can range from a few weeks to a couple of months. However, dogs that undergo chemotherapy to treat lymphoma can often achieve a mean survival time of over a year.

The survival time is extended, and dogs feel better when their cancer burden is lessened. This extra quality and quantity of life can be extremely valuable to dog owners and can improve the human-animal bond.

Knowing what to expect with chemotherapy will empower you to make the best decision for your dog with cancer.

What Happens in Dog Chemotherapy

Many dog lovers are curious about what happens when a dog gets chemotherapy. Depending on a dog’s type of cancer, a specific chemotherapy protocol will be recommended. The oncology team will recommend the most effective treatment for that particular type of cancer based on published research done on other patients with a similar cancer diagnosis.

Many different factors are considered when choosing a chemo protocol for a dog. These include:

• Finances
• Cancer type
• Cancer staging
• The amount of required veterinary visits
• A patient’s tolerance of veterinary visits
• Age
• Comorbidities (other health problems)
• Possible adverse side effects

Chemotherapeutic drugs come in different forms, including oral or injectable medications. Depending on the drug, they can be given orally, subcutaneously (under the skin), intramuscularly (into the muscle), or intravenously (into a vein).²

Routine lab work will be done before chemotherapy treatment to ensure the patient’s immune system can tolerate chemotherapy well. Other monitoring that may be performed includes:

• A urinalysis to check for infection or blood in the urine
• An electrocardiogram or echocardiogram when cardiotoxic drugs are administered
• Imaging to ensure that the cancer has not spread

Once it is determined that a dog is well enough for chemo administration, proper precautions should be used in order to administer the chemotherapy safely.

Oral Chemotherapy for Dogs

For oral medications, it is recommended that gloves be worn by the person administering the chemotherapy. Tablets should never be crushed or split. Chemotherapy pills should be handled in a well-ventilated area, or a respirator should be used to avoid inhalation.³

Your veterinarian may give the chemotherapy pill in the hospital or send the meds with you to give at home more frequently.

Intravenous Chemotherapy for Dogs

For intravenous chemotherapy, it is important that chemotherapeutic drugs are prepared in a biochemical safety cabinet or in a quiet room on a clean surface away from drafts. Anyone administering chemotherapy should wear proper PPE (personal protective equipment), including a suitable mask, a chemotherapy gown, chemotherapy gloves, and protective eyewear.

Although chemotherapy is valuable in treating cancer, chronic exposure to chemotherapy by those administering it can cause adverse effects and is considered unsafe. It is imperative that proper safety practices are followed. This is why these drugs are only handled and administered by trained veterinary professionals.

Depending on the drug(s) your dog is receiving, the veterinary team will prepare the chemotherapy before you arrive for your dog’s appointment, or they may prepare it after you arrive.

Another important aspect of safe chemotherapeutic administration involves catheter placement. An IV catheter should be placed in a healthy vein. If the vein has been recently used or is damaged, the catheter should be placed in a different location – this limits the risk of the drug leaking out of the vein and harming your dog’s other body tissues.² Several of the chemotherapeutic drugs are very damaging to the surrounding tissues if they are leaked outside of the vein, so precise catheter placement is necessary.

Additional safety is achieved using closed system transfer devices (CSTDs). These CSTDs eliminate the need for needles, and they reduce the potential for chemotherapeutic drugs to be leaked or aerosolized into the surrounding environment.

Once the catheter has been placed, the veterinary team will start the chemo infusion. Some drugs can be given quickly, but many must be given slowly over time to limit any side effects for your dog. Some dogs may need to be sedated to help them stay calm during their chemo treatment, as they will need to stay relatively still during this time.

Once the IV chemotherapy has been administered, the catheter is removed, and all supplies are disposed of in accordance with the law. And your dog is ready to go home and rest!

Common Examples of Dog Chemotherapy

There are three primary types of chemotherapy used in dogs: conventional injectable chemotherapy, metronomic chemotherapy, and targeted chemotherapy.³ Each type of chemotherapy has different pros and cons.

Conventional Chemotherapy

The goal of conventional chemotherapy is to utilize the maximum tolerated dose of a chemotherapeutic agent over a predetermined period of time. A common example of conventional chemotherapy is the CHOP protocol for treating lymphoma. This multi-agent protocol utilizes a prescribed dose of chemotherapy for a predetermined period of time of 15 or 19 weeks.

Metronomic Chemotherapy

Metronomic chemotherapy is defined as the uninterrupted administration of low doses of cytotoxic drugs at regular and frequent intervals. Potential benefits of metronomic chemotherapy include less expense, less toxicity, and fewer trips to the veterinary hospital since these medications are administered orally at home.

Lab work should still be monitored every 3-6 weeks while on metronomic chemotherapy. Cyclophosphamide, chlorambucil, and lomustine (CCNU) are three examples of drugs that are used in metronomic chemotherapy protocols.

Targeted Chemotherapy

In recent years, targeted chemotherapeutics have been incorporated into certain cancer treatment plans with the intention to attack a “target” on a cancer cell while doing less damage to healthy cells. These chemotherapeutics can be prescribed as a sole agent but are generally used in conjunction with surgery, conventional chemotherapy, or radiation therapy.

An example of a targeted chemotherapeutic used in veterinary medicine is the drug Palladia. Palladia targets and inhibits the tyrosine kinase receptor on overactive cancer cells. Blocking or inhibiting these receptors can slow down cancer growth.

Single-Agent vs. Multi-Agent Protocols

Another way to classify a chemotherapeutic protocol is to define it as a single-agent or multi-agent protocol. A single-agent protocol is one in which a single chemotherapeutic drug is given alone. A few examples of chemotherapeutic agents that can be used as a single agent include:

• Alkylating agents: cyclophosphamide, chlorambucil, lomustine
• Anti-metabolites: methotrexate, cytosine arabinoside
• Antitumor antibiotics: doxorubicin, mitoxantrone
• Corticosteroids: prednisone, prednisolone
• Platinum compounds: cisplatin, carboplatin
• Plant alkaloids: vincristine, vinblastine
• Other miscellaneous agents: Tanovea, L-asparaginase

A multi-agent protocol is one in which multiple drugs are used in combination to have the best defense against abnormal cancer cells. Utilizing drugs with different mechanisms of action in conjunction with each other has a better chance for achieving and maintaining remission. Chemo agents are like weapons used for battle. When more weapons are used to attack abnormal cancer cells, the cancer has a harder time fighting back, and multidrug resistance is delayed.

Listed below are a few examples of multi-agent protocols used for the treatment of lymphoma:

• CHOP: cyclophosphamide (C), doxorubicin (H), vincristine (O), and prednisone (P)
• L-CHOP: L-asparaginase with the agents used in CHOP
• MOPP: mechlorethamine (M), vincristine (O), procarbazine (P), and prednisone (P)
• LOPP: lomustine (L), vincristine (O), procarbazine (P), and prednisone (P)
• COP: cyclophosphamide (C), vincristine (O), and prednisone (P)

When is Dog Chemotherapy Recommended?

In most cases, chemotherapy is used to treat patients with widespread disease, for tumors sensitive to drug therapy, or for potential metastatic disease that is not amenable to local therapy such as surgery or radiation therapy.

Chemotherapy drugs circulate throughout your dog’s body and can target cancer cells anywhere, so they are most useful for systemic treatment. Surgery and radiation, on the other hand, typically target discrete tumors.

The goal is to prolong survival while maintaining an excellent quality of life for patients during and after treatment.⁶

How Chemotherapy Works

Chemotherapeutic agents can be used to increase both the length and the quality of life for patients with a wide variety of neoplastic diseases.⁶ Chemotherapy aims to stop cancer cells that are continuing to divide uncontrollably, and it aims to kill rapidly dividing cells.^2,14

Chemotherapy in the treatment of cancer can have different goals:¹⁴

• Curative chemotherapy aims to eliminate all cancer cells from the body and make cancer go away completely. Curative chemotherapy is utilized more often in human oncology. Higher doses are given with the goal of “cure cancer.” These higher doses often yield greater side effects than would be considered unacceptable for most dog lovers.
• Adjuvant chemotherapy mainly aims to fight the cancer cells that could be left in the body after surgery but can not be detected (microscopic disease). The goal of this type of chemotherapy is to prevent recurrences.
• Neoadjuvant chemotherapy can often shrink the tumor enough for it to be surgically removed or for it to be removed using less invasive surgery. Neoadjuvant chemotherapy is reserved for those tumors too large for surgical removal in their current state.
• Palliative chemotherapy: Chemotherapy is considered palliative when removing all cancer cells is no longer possible. Chemotherapy can still help to relieve certain symptoms, slow down the progression of the disease, stop the disease temporarily, and avoid complications.

Cancers Chemotherapy Is Commonly Used For

Chemotherapy is indicated for treating tumors known to be sensitive to drug therapy (such as hematologic malignancies) and for highly metastatic malignancies.

Examples include:

• Lymphomas
• Leukemias
• Multiple myelomas
• Osteosarcoma
• Hemangiosarcoma
• High-grade mast cell tumors

For solid tumors, chemotherapy is often used after the surgical removal of the primary tumor in order to slow any microscopic metastasis.^3,6

How to Get the Best Results

Your oncologist and veterinary team will handle most of the logistics of chemotherapy treatment, but you also play a vital role in your dog’s care. Here are some things you can either do yourself or approve for the veterinary care team to do to help improve the odds of your dog’s chemo treatment being successful.

• Get an accurate diagnosis and ensure the tumor type is known to respond to chemotherapy.
• The patient should undergo the appropriate staging tests such as thoracic radiographs, an abdominal ultrasound, a CT scan, bloodwork, etc., as indicated by the tumor type. Staging allows the clinician to evaluate the extent of the disease and may provide information that changes the treatment plan.
• The patient should be stabilized as much as possible before treatment with a chemotherapeutic agent. Although chemotherapy is generally well tolerated in veterinary medicine, if an animal is unstable or ill, the likelihood of adverse events becomes higher. Abnormalities in hydration status, electrolyte balance, kidney function, liver function, anemia, etc., should be corrected before starting chemo if possible. However, remember that some of the patient’s medical problems will only be corrected by treating the cancer itself.
• Know the proposed treatment’s cost, dosing schedule, and potential toxicities beforehand. You must be committed and comfortable with the protocol for the best outcome possible. If a particular protocol isn’t feasible for you, your veterinarian can recommend a different one that will better fit you and your dog.
• Explore and discuss any other treatment options thoroughly before making a decision.
• The nutritional status of all oncology patients should be assessed at the beginning of and throughout the course of treatment. Good nutrition is necessary for the body to be able to fight cancer. Your oncologist or veterinarian may do this assessment or may recommend a consult with a veterinary nutritionist.
• Keep an open dialogue with your veterinary team to ensure that the quality of life of your dog remains the ultimate goal. Tell the vet about any side effects or challenges that crop up so the treatments can be adjusted as needed.
• Provide your vet and/or oncologist with a complete list of all medications and supplements that your dog is receiving.

Drug and Supplement Interactions

The interaction between cytotoxic drugs and most homeopathic remedies is not known.⁴ Therefore, your veterinarian should be consulted before giving any homeopathic remedies³ or starting any new supplement.

In human medicine, antacids that contain aluminum and magnesium, antibiotics, anticoagulants, anticonvulsants, antifungal agents, antiretroviral agents, corticosteroids, antiemetics (Ondansetron), and herbal supplements have all been found to interact with some chemotherapeutic agents.¹²

Home Care After Dog Chemotherapy

There isn’t usually much home care needed after a chemotherapy treatment, as side effects are less common thanks to the lower doses used for veterinary patients.

Although adverse reactions and side effects are less common in animals receiving chemotherapy, some animals experience gastrointestinal upset. Therefore, medications may be prescribed to prevent diarrhea and vomiting and improve appetite. Food should be palatable to encourage your dog to eat full meals.³

Follow-Up

Regular follow-up will be needed depending on the diagnosis and treatment plan. Some tests may be repeated weekly to ensure that your dog tolerates and responds to the treatment, while other tests will be done less often.

At the very least, patients should be seen regularly for hematological monitoring (bloodwork).⁴ A complete blood count ensures an adequate white blood cell count. It is generally accepted that an absolute neutrophil count of greater than 2000 cells per microliter and greater than 50,000 platelets per microliter should be present prior to chemotherapy administration to minimize the risk of sepsis or other complications.⁸

Tests such as an echocardiogram and an EKG can screen and monitor patients being treated with doxorubicin to ensure their heart is functioning normally.⁶

A chemistry panel is performed routinely to evaluate kidney and liver function since these organs are necessary for metabolizing various chemotherapeutic drugs.

Because sterile hemorrhagic cystitis is a risk with cyclophosphamide, urine should be monitored with periodic urinalysis.³

Even if your dog is getting chemotherapy from an oncologist, follow-up appointments and testing can often be done through your regular veterinarian.

When to Not Use Chemotherapy

Chemotherapy is not appropriate for every cancer or for every patient.

The veterinary team can access peer-reviewed published studies demonstrating appropriate and efficacious cancer treatment plans. These studies should guide treatment decisions. If your dog’s cancer type does not respond to chemotherapy, it is probably not worth the financial cost or the risk of side effects to give it anyway.¹

Many chemotherapy drugs are metabolized and eliminated by the liver and kidneys, so animals with pre-existing renal or hepatic disease may experience increased toxicity or decreased efficacy. Dosages may need to be adjusted in these patients.⁶

Risk versus benefit should always be considered. Ask your practitioner for details on how a chemo protocol has been performed in dogs with the same cancer as yours, what risks are involved, and how much time you are likely to gain by pursuing treatment.

Where to Get Chemotherapy for Dogs

General practice veterinarians with extensive knowledge of oncology and chemotherapy safety can administer chemotherapy. Still, referral to a specialist may be appropriate if the primary care veterinarian or you yourself wish to consider all possible treatment options or when the referring veterinarian cannot provide optimal treatment for any reason.³

The best outcome occurs when general practice veterinarians and oncologists can collaborate together with the mutual goal of the patient’s well-being.

Safety and Side Effects

When dosed appropriately, chemotherapy can be administered safely. Since chemotherapy drugs do not differentiate between killing tumor cells and normal cells, following published guidelines for treatment is critical.

Most dogs tolerate chemotherapy well. Potential adverse effects include:

• Mild to moderate nausea
• Mild to moderate vomiting
• Mild to moderate diarrhea

All of these are easily treated with supportive care or symptom management.

In rare instances, life-threatening complications related to chemotherapy-induced myelosuppression (bone marrow suppression) can develop. This requires hospitalization and aggressive supportive care.⁸

Specific side effects can result from certain drugs. For example, doxorubicin can cause cardiotoxicity or damage to the heart. Cisplatin can cause fatal pulmonary edema in cats or renal toxicity (kidney failure) in dogs.² The side effects are minimized by following preset guidelines about safe dosing and administration.

Chemotherapy can also be mutagenic and carcinogenic, posing a public health risk if not handled correctly.¹ Safety measures that should be observed include the following:

• Strict adherence to published guidelines regarding personal protective equipment (PPE) worn by individuals administering chemotherapy.
• Immunocompromised individuals and women who are pregnant or breast-feeding should avoid working with chemotherapeutic agents.³
• No food or drug should be in the chemotherapy administration room.
• Once the drug is administered, all chemotherapy waste, such as syringes, IV catheters, bandages, etc., should be returned to the sealed plastic bag and disposed of with other biohazardous waste according to government regulations. Chemotherapy waste should not be thrown into the sharps container or garbage.
• A protocol and supplies (spill kit) for cleaning up hazardous materials should be readily available should a spill occur.²
• Since patients excrete potentially harmful drugs and their metabolites into urine, feces, vomit, and saliva for variable periods following injectable or oral chemotherapy administration, food bowls and bedding should be washed separately if accidents occur. After receiving cytotoxic drugs, dogs should be encouraged to urinate and defecate on a separate area of grass.⁴ Owners should wear gloves when cleaning up after their dogs for up to 72 hours after intravenous drug administration and wash the area with diluted bleach.²

Cost of Chemotherapy for Dogs

According to the Veterinary Cancer Society, dog chemotherapy costs can vary with a range of $150-$600 or more per dose.¹⁵ This fee will certainly depend upon the drug used, the route of administration, the size of your dog, and the geographical location of the dog being treated.

The veterinary team should discuss the cost of treatment with you and receive consent before proceeding. It is important to understand that there are many published protocols for cancer treatments and dogs. It will be up to the veterinary team to discuss treatment costs and support the plan that makes the most sense for each patient.

In some cases, cancer treatments can cost as much as $10,000 in total. These costs are often spread out over the course of treatment after the initial diagnosis is made.¹⁶