Cat Chemotherapy Cost, Side Effects, and Recovery

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Chemotherapy medications are those that are used to treat different types of cancer. In this article we will aim to provide an overview of what chemotherapy looks like in cats. How do they handle it? What side effects might I expect? How much does it cost?

We will also briefly review some of the most common chemotherapy medications used in cats. Links to more in-depth information about each medication will be provided, if available.

About Chemotherapy Medications for Cats

A chemotherapy medication is one of several classes of medications used to treat cancer. In most cases, chemotherapy medications work by targeting quickly dividing cells.

Cancer cells tend to multiply and grow rapidly. So by using medications that target quickly multiplying cells, cancer growth and spread may be significantly slowed down.

The goal of cancer treatment in cats is rarely to fully cure the condition. This may be possible if a cancerous mass was removed by surgery and chemotherapy is prescribed to “clean up” anything remaining.

But in many cases, lymphoma for example, surgery is not a practical option. Cancer may have already spread to other places in the body by the time it is found. This makes the main goals of chemotherapy to slow down the cancer’s growth and spread and to provide the best quality of life for as long as possible.

Depending on how your cat’s cancer diagnosis was determined and what type it is, you may pursue care through your primary care vet. Your vet may also instead refer you to a veterinary oncologist (cancer specialist) for further care.

There are several chemotherapy medications used in cats. The following list is organized by how they are given.

1. Oral Medications

When we think of chemo, we often think of recurrent, stressful and intensive doctor visits. But there are several oral chemotherapy medications that can allow treatment from the comfort of home.

Prednisolone

Prednisolone is a steroid. Steroids are used for many medical conditions from treating inflammation to suppressing immune reactions. They can also be helpful for treating certain types of cancers, especially lymphoma.

We don’t always think about pred as a chemotherapy medication, but it is often a core part of chemotherapy protocols, such as CHOP and COP for lymphoma. While prednisone and prednisolone are similar, prednisolone is always preferred in cats due to metabolism differences compared to dogs and people.

Chlorambucil

Chlorambucil is used to treat chronic lymphocytic leukemia and small cell lymphoma. Small cell lymphoma tends to be present more diffusely, especially in the gastrointestinal tract, as opposed to being a single tumor. Many veterinarians consider small cell lymphoma and inflammatory bowel disease to be similar conditions but on different spectrums of severity (small cell lymphoma being the more severe).

Lomustine (CCNU)

Lomustine is used to treat mast cell tumors and lymphoma, especially large cell lymphoma. Large cell lymphoma can present as a single large mass and tends to spread more aggressively.

Cyclophosphamide

Cyclophosphamide may be used for a variety of cancer conditions where tumors are involved. This may include lymphoma, mammary tumors, and injection-site associated sarcomas. It is part of the CHOP or COP protocols for treating intermediate or large cell lymphoma.

Ifosfamide

Ifosfamide has a narrower use for injection site-associated sarcomas. Fortunately, we see less of these types of tumors than we used to.

2. Intravenous Medications

These injectable medications are routinely administered by veterinary oncologists. They require specialized, careful, and safe handling. While general practice vets may find a way to make accommodations for certain patients, administering IV chemotherapy is uncommon for your regular vet to do.

Doxorubicin

Doxorubicin is used as part of treating lymphoma tumors, carcinomas, and sarcomas. It is part of the CHOP protocol for intermediate and large cell lymphoma.

Mitoxantrone

Mitoxantrone is used for a couple of different cancers including lymphoma, mammary tumors, and squamous cell carcinoma.

Carboplatin

Carboplatin is used for a variety of carcinomas and sarcomas.

Vincristine

Vincristine is most often used as part of the CHOP or COP protocols for treating intermediate or high grade lymphoma in cats.

Vinblastine

Vinblastine is similar to vincristine, also used mostly to treat lymphoma. It has also been used for treating mast cell tumors. It may be used as an alternative to vincristine in cats that have a harder time with GI side effects.

3. Other Injectable Medications

L-Asparaginase

L-asparaginase is not given intravenously. It is instead given as an injection either in the muscle or under the skin. Lymphoma tumors have a higher need for the amino acid L-asparagine compared to normal cells. Normal cells can also make L-asparagine on their own while lymphoma cells have a limited ability to do so. By depleting L-asparagine, this medication can help selectively kill lymphoma cells.

Dosing Information for Cats

Dosing can vary widely among chemotherapy medications. This can depend on the type of cancer being treated, your cat’s body weight, and how they are tolerating the medication. You should never start a chemotherapy medication at home for your cat without consulting a veterinarian or veterinary oncologist.

While many medications for cats are dosed on a milligram per pound or milligram per kilogram basis, chemotherapy medications are dosed differently. It is more common to dose them based on body surface area, or milligrams per meter squared. This requires converting a cat’s weight in kilograms to mg/m2 using a conversion chart.

The goal of any chemotherapy treatment is to slow down tumor growth or cancer spread effectively while mitigating side effects as much as possible. The dose or frequency of medication may be adjusted if side effects are more than mild or transient.

If you feel your cat’s chemotherapy dose needs adjustment or if you think the next treatment should be delayed, always make sure to check first with your veterinarian or veterinary oncologist.

Your cat’s care provider may advise having lab work checked either after a treatment is given or shortly before the next is due. It is extremely important to keep these appointments so they can make the best decisions for your cat on treatment frequency or dosing.

How Chemotherapy Medications Are Administered to Cats

Many people think of chemotherapy looking like this, with an intravenous catheter in a hospital setting. But oral chemotherapy medication given at home is also very common. Tomasz Koryl / Shutterstock.com

Oral chemotherapy medication can be given just like any other oral medication. But there are some precautions that must be taken. Chemotherapy medications might not be prescribed for daily administration. Some, like chlorambucil or lomustine, are given only once every couple of weeks.

It’s extremely important that your cat gets the dose, especially if it’s the only dose being given for a couple weeks. If you can’t be sure your cat will take the dose hidden in food or a treat, you may have to give it directly by mouth.

I have also arranged to have patients come into our office so that one of our licensed technicians can administer the dose during a brief tech appointment, to ensure a cat receives their medication.

When giving chemotherapy medication, it’s important to realize that with the exception of prednisolone, all of the others are designed to attack rapidly dividing cells. This is important for a patient with cancer but not someone healthy. When administering chemotherapy medication to your cat, it’s important to wear gloves to protect yourself from any inadvertent contact with the drug.

For the first 24-48 hours, chemotherapy will still be in your cat’s system and passed in the urine and stool. Make sure to wear gloves when cleaning the litter box for 2 days after your cat’s last dose or treatment. The same goes for any elimination accidents that may occur at home.

Side Effects of Chemotherapy for Cats

This is the section that is of most concern to pet parents. Much of the worry about chemotherapy side effects comes from experience on the human side. Whether it is personal experience or that of a friend or family member, chemotherapy is notorious for making people feel ill. Then there’s the other negative effects like losing all your hair.

The concern about potential side effects is the most common reason, next to cost, that someone will decline pursuing chemotherapy for their cat. There is often the vision of a beloved cat having their life prolonged only to live with pain and sickness the whole time.

But in contrast to people, pets handle chemotherapy much better. And even among pets, cats handle it better than dogs.

Many cats receiving chemotherapy may show no significant side effects. About 15% may develop mild side effects. These can be a temporary downturn in appetite or some loose stool for a couple days.

5% of cats will experience more moderate side effects that may require additional medications to assist with. This may include an appetite stimulant for loss of appetite or an anti-nausea medication to help with appetite and prevent vomiting.

These effects may also be enough to require skipping a dose of chemo or delaying a treatment but do not require stopping treatment altogether.

Effects called myelosuppressive effects can occur from chemotherapy. This means production of red blood cells, white blood cells, and platelets in the bone marrow is affected. This is an important reason why complete blood count (CBC) lab work is checked periodically during chemo treatments. A chemo dose or treatment may be delayed if a CBC shows a downturn in cell production.

About 1% of cats may experience more severe effects of chemotherapy. This can include effects like unexpected drug reactions or an allergic response. In these cases, a complete change to the chemo medications may be needed or treatment may need to be discontinued.

From the list of more common chemotherapy medications used in cats, here are some side effects that may occur.

Prednisolone

Cats tolerate prednisolone quite well, especially compared to people and dogs. You may see an increased need to drink and eat but this is usually modest in cats. As a result you may see more deposits in the litter box. Weight gain can occur as a side effect of a steroid over time. This can often be an advantage for cancer patients who are prone to losing weight.

Prednisolone should be used carefully in cats at risk for heart disease. Overweight cats at risk for diabetes should also be monitored carefully on prednisolone.

Chlorambucil

Chlorambucil is generally well tolerated. It may cause some mild myelosuppressive effects. These can be managed safely with periodic blood work checks. GI upset may occur but is not common or severe.

Lomustine (CCNU)

The most common side effect for lomustine is a drop in neutrophils, a type of white blood cell, and platelets.

Liver toxicity and digestive upset are seen in dogs, but occur much less frequently in cats.

Given once every 3 weeks, I have seen it cause a temporary drop in appetite for 3-4 days, manageable with an appetite stimulant.

Cyclophosphamide

Bone marrow suppression is the biggest risk of lomustine but is considered dose dependent. This means that if myelosuppression is seen on bloodwork, this may be alleviated with a lower dose.

In dogs it can cause bleeding of the bladder wall, but this is not a great concern for cats. But because cats can often exhibit abnormal urinary behavior, especially when they are unhappy or ill, it would be important to rule out cyclophosphamide as a potential cause.

Ifosfamide

Ifosfamide’s main side effect is a low neutrophil count, which can be severe and is dose-dependent. It can also cause nausea and poor appetite. Ifosfamide is related to cyclophosphamide but does carry a higher risk for bladder bleeding. To help reduce this risk, it is often given with a high rate of intravenous saline to flush the bladder. A medication called mesna is also given that reduces the risk.

Because of the need for intravenous fluids, ifosfamide may not be appropriate for cats with heart disease or another condition that doesn’t tolerate a high IV fluid rate.

Doxorubicin

Doxorubicin can cause neutropenia and loss of appetite. Doxorubicin can carry a risk for kidney injury and failure with higher doses and with longer-term cumulative effects. Doses are capped at a certain level to reduce this risk.

Heart disease risks seen in dogs are not reported in cats.

Mitoxantrone

Mitoxantrone can cause digestive upset including vomiting, diarrhea, and poor appetite. Compared to doxorubicin, it can cause more myelosuppressive effects. On the flip side though, it carries less risk for kidney injury.

Carboplatin

Carboplatin can carry a risk of neutropenia. There can be kidney injury risk, but more so in cats with pre-existing renal disease. Kidney values are regularly monitored during treatments with this medication.

Vincristine

Vincristine can carry risk of more significant gastrointestinal upset and poor appetite. However, bone marrow suppression side effects are uncommon. A peripheral neuropathy or nerve condition affecting the limbs, has also been reported.

Vinblastine

Vinblastine has something of reverse side effects compared to its cousin vincristine. Vinblastine has more myelosuppressive effects but is kinder on the GI tract. An oncologist may choose which one to use based on a cat’s risk for one effect or the other.

L-asparaginase

Side effects to L-asparaginase are minimal. However, as a protein introduced to the body, an anaphylactic response is possible. Cats will be monitored for this risk after injection, usually before they leave the hospital.

Tumor cells may develop resistance to L-asparaginase’s effects, making it less effective over time.

Do Cats Lose Their Hair on Chemo?

Cats (and dogs) generally do not lose their hair. At least not the way people do. The reason people lose their hair is that human hair continuously grows. Hair cells rapidly divide and so are affected by chemo.

In cats and dogs, a hair will grow to a certain length, then stop growing. After a time, the hair will fall out. When hairs stop growing, they can no longer be affected by chemo. So it is true that some hairs may fall out that are in their growth phase, but this is usually not clearly noticeable overall.

Cats can often lose their whiskers with some chemotherapy treatments. This will not affect your cat greatly, and the whiskers will grow back if a chemo treatment is finished.

Recovery From Chemotherapy for Cats

Recovery from chemotherapy requires close contact and follow-up with your vet or veterinary oncologist to support a good quality of life for your cat between treatments or after treatment is finished. Sata Production / Shutterstock.com

Chemotherapy protocols differ depending on the type of cancer being treated. Some may be for several weeks and then discontinued. Others may need to be continued for the cat’s life.

Many chemotherapeutics are given in cycles, so cats have a recovery period of a couple days, then are expected to do well until their next dose.

If your cat experiences digestive side effects, these are limited in most cases. Additional medications like those for nausea, vomiting, and diarrhea can help with the symptoms until they resolve. We expect after the first couple days that a cat has a good quality of life until the next treatment is needed.

Overdose and Emergencies

If you’re concerned your cat may have developed side effects while using any chemotherapy medication or if you are worried about an overdose, make sure to immediately contact one or more of the following for advice:

• Your veterinarian or veterinary oncologist
• ASPCA Animal Poison Control Center (1-888-426-4435)
• Pet Poison Helpline (1-855-764-7661)

If your cat is receiving chemotherapy treatment through a veterinary oncologist, I find it is best to call them first for concerns about general side effects. They will be the most knowledgeable about what to expect and what is acceptable for your cat’s particular case and what would be cause for significant concern.

Potential Drug Interactions With Chemotherapy Medications

Each chemotherapy medication can have its own list of medications it interacts with. When a chemotherapy plan is being developed for your cat, it is extremely important that your veterinarian or veterinary oncologist is aware of any other medications or supplements your cat is taking.

There are a couple of broad categories that require caution if your cat is receiving a chemotherapy medication.

Vaccinations

Vaccinations work by stimulating the immune system to develop antibodies or a similar response. Chemotherapy medications can have a hard effect on the immune system. This is usually closer to when a dose or treatment is given.

Vaccinations may not need to be discontinued but most oncologists will recommend that they are given during an “off week” between doses or treatments.

Other medications suppressing the immune system (apoquel, atopica)

Because chemotherapy medications can affect the immune system, they must be used carefully with any other medications that can have similar effects. Cyclosporine (Atopica) for example is commonly prescribed for cats with allergic skin disease or another immune disorder. It may need to be discontinued with some chemo medications.

Also Read: Common Skin Problems in Cats: Causes and Treatments

A veterinary oncologist will provide you with the best opinion on what medications can be continued if your cat is starting chemotherapy.

Cost of Chemotherapy for Cats

Next to concerns about side effects, concern about cost of chemotherapy is understandably paramount for owners of cats with cancer.

Chemotherapy to many is synonymous with very high cost. This isn’t completely untrue. If the best way to treat a certain cancer is injectable chemotherapy requiring repeat oncology visits for treatment and testing, the cost can be high.

According to Embrace pet insurance, full treatment may cost anywhere from $1000 to $5000. Care credit likewise states that full chemo for cats averages over $3-4000. Each treatment session may cost a couple hundred dollars up to several hundred dollars.

Besides the medications themselves, these costs usually also include blood work rechecks, which oncologists will require shortly after or before treatments.

Recheck testing to stage a particular cancer may also be needed. This can include x-rays and ultrasound exams to re-evaluate a tumor’s size or how much of it has spread to other parts of the body. Sometimes, costs might be mitigated by having recheck testing done at your primary care vet.

Keep in mind that these more comprehensive treatments often have the best success rates.

But while full courses of chemo through an oncologist can be very expensive, other options may be available. There is often more than one approach to treat a particular cancer. And it’s important to realize that especially with oral chemo, the cost options can be much more reasonable.

Nearly all oral chemotherapy medications need to be ordered through a compounding pharmacy. The drug doses for most are too high for cats or come in a form that is impractical. Compounding can allow for liquid or even chew treat form options. Multiple flavor options are possible too.

Here is an approximate cost breakdown for an average 10 lb cat, for some common oral chemotherapy medications through a compounding pharmacy I routinely use. Keep in mind that costs may vary between pharmacies.

Cyclophosphamide

At about 50mg for a 10lb cat, the cost is about $50 for 7 capsules. For a liquid form, a 100 mg/ml concentration in a 5ml bottle (providing about 10 doses) costs about $70.

Chlorambucil

With 5mg per cat given every 2 weeks, the cost is about $60 for 6 capsules.

An alternate protocol where a lower dose of 2mg is given every other day, it costs about $60 for 30 capsules (2 months worth).

Lomustine (CCNU)

For about 13-16 mg given every 3 weeks, the cost for 4 capsules is about $70.

For the liquid form, in a 10 mg/ml concentration, 10ml (or 6 doses) costs about $84.

In each case, you’re looking at about 3-4 months worth of treatment.

Prednisolone

From my own office, Prednisolone costs about $40-50 for 30 of the 5mg tablets. Costs may vary from office to office. However, at human pharmacies, the cost for prednisolone is considerable where 30 of the 5mg tablets can cost hundreds of dollars. While human pharmacies are often perceived as a bargain by pet owners, this is one medication you may want to get directly from your vet.