Cancer affects animals as well as people, but sometimes treatment options are available which can help. Depending on the type of cancer your cat is suffering from, they may be able to receive chemotherapy. If this is something your vet has mentioned to you, then you probably have a lot of questions. In this article, we will look at chemotherapy in cats, specifically focussing on a common concern from owners – whether it is cruel to put your pet through it.

How does chemotherapy work?

There are a variety of different cancers that cats can suffer from. Some of which will respond to chemotherapy, but not all. Many cancers do best with surgery and might be cured with this alone. But some may require follow up treatment to destroy any malignant cells that may have been left behind.

Chemotherapy describes a variety of medications that are aimed at killing cancer cells. These cells are usually rapidly reproducing, and the drugs will target those. In cats, this can help to slow the progression of the disease and extend your pet’s life span, sometimes leading to remission.

This type of treatment is usually recommended for cats that have cancer in multiple areas of the body, such as lymphoma (a cancer of the lymphatic system). Or those that are at risk from malignant cells spreading elsewhere in the body from a primary tumour.

What types of cancer can chemotherapy be used against?

Chemotherapy is used for cancers that are rapidly spreading, as these fast-growing cells are the most sensitive to the cytotoxic drugs. Cancers that are malignant and likely to spread through the body (e.g through the lymphatic system) will usually be the most susceptible to this type of treatment.

Not all cancers will be suitable for this type of treatment. Slow growing or benign masses are unlikely to be treated with chemotherapy. Your vet will be able to advise you further.

How is chemotherapy administered?

There are different types of chemotherapy drugs administered to cats, depending on the cancer type they have been diagnosed with. Some drugs may need to be administered orally in tablet form, whereas others are given by a vet, directly into the bloodstream via a drip or catheter. Quite often a combination of drugs may need to be given. It may be used alongside other measures such as surgery or radiation therapy.

There may be repeated trips needed to the hospital for your cat to have drugs administered or blood samples taken, to ensure treatment is being effective and not causing any unwanted issues. The exact frequency will depend on your cat’s individual treatment protocol.

Are there any side effects from chemotherapy?

As with any medication, there is always the potential for side effects. However, the majority of cats tolerate chemotherapy very well.

The most common issue seen would be gastrointestinal upset such as vomiting or diarrhoea. This can usually be managed through supportive treatment like antinausea drugs and easy-to-digest food. Suppression of the bone marrow can also occur, leading to a reduction in infection-fighting white blood cells. This will usually be monitored through blood samples, with drug doses being adjusted if levels drop too low.

Cats don’t lose hair in the same way that people do, though you may find any areas that have been shaved (e.g. for surgery or blood samples) may be slower to grow back than usual. Some cats may lose their whiskers during treatment too.

Is giving chemotherapy to cats cruel?

Vets wouldn’t advise treating your cat with chemotherapy if they deemed it cruel. Many cats tolerate the actual drugs quite well. However, there are some situations where chemotherapy may not be recommended.

If your cat has a difficult temperament and gets very stressed by visits to the vet, then repeated visits to the practice could be considered unkind. We can’t explain to cats what these visits are about, and they won’t understand that we are trying to help extend their life. Cats live in the moment and don’t look forward to things in the same way that we do (e.g. their next birthday). If the stress of treatment is outweighing any benefits, then a discussion needs to be had.

The other time that things may be ethically questionable is if your cat has been given a very poor prognosis. If the chemotherapy is unlikely to be successful, or if it will only extend your pet’s life by a matter of weeks, then it may be kinder not to embark on treatment and just enjoy your pet’s remaining days.

Each case is individual so there may need to be a discussion about the pros and cons of treatment, which you can chat through with your vet.


Chemotherapy can help to extend your pet’s life following a cancer diagnosis, or in some cases even achieve remission. However, this needs to be balanced with other factors such as your cat’s temperament, plus your own financial considerations. If you have any questions specific to your cat’s treatment, then don’t hesitate to speak to your vet.