Chemotherapy for
your pet

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A guide to chemotherapy and the veterinary patient

What is chemotherapy?

Chemotherapy is the giving of drugs that are toxic to cancer cells. These drugs can be given in a number of ways – intravenously, under the skin or orally (tablets or capsules).

How does chemotherapy work?

Cancer cells generally multiply and grow very rapidly. Most chemotherapy drugs work by damaging these cells, so that when they divide, they will die. Unfortunately, normal cells can also be affected, however, these normal cells are able to recover better than cancer cells.

What are the benefits of chemotherapy?

  • Chemotherapy is used by veterinary oncology Specialists to treat a number of cancers. The type of drugs used and the way in which they are administered depends on the type of cancer and whether or not other treatments are also required.
  • Chemotherapy is the most effective single treatment for some types of cancer, offering the best opportunity for gaining control over it (remission), whilst ensuring that the patient has a good quality of life. An example of this type of cancer is lymphoma (lymophsarcoma).
  • Chemotherapy is often recommended following the surgical removal of a cancer. The purpose of chemotherapy in this instance is to prevent local regrowth of the cancer and in addition, to prevent or slow down the spread of cancer (metastasis). An example of a cancer where chemotherapy is used after surgery is the malignant bone tumour, osteosarcoma.
  • Chemotherapy is sometimes given to patients in conjunction with radiotherapy. An example of a cancer where both radiotherapy and chemotherapy are used together would be for certain patients with mast cell tumours.
  • Chemotherapy can be used alone for the treatment of cancers that cannot be removed with surgery or controlled with radiation, or in cases where the cancer has already spread, resulting in secondary cancers (metastases). In some patients with mast cell tumours, this is the recommended treatment.

How is chemotherapy given?

After the initial examination by a cancer Specialist, the course of treatment will be discussed with you and a therapy plan will be outlined. The Specialist will discuss with you any additional test that may be required before treatment commences. Treatment for each patient is individually planned.

Most of the chemotherapy drugs used at Southfields Veterinary Specialists are given into a vein, requiring the placement of a small catheter. Chemotherapy treatments are usually carried out on an out-patient basis, so you will need to allow approximately 1 hour for your appointment. Blood tests will be carried out before each treatment.

On occasion, an overnight stay may be required, but should this be necessary, your Specialist will discuss this with you.

Some drugs can be given at home as they are in tablet or capsule form. Remember that chemotherapy is potentially dangerous, even at low doses! We will always provide you with advice about handling the chemotherapy drugs and how to manage your pet whilst they are receiving chemotherapy. Tablets should never be crushed, split or sprinkled and gloves should be worn at all times when handling them.

How is chemotherapy given?

The length of time and frequency of chemotherapy treatment will depend on the type of cancer being treated and how well the treatment is tolerated by the patient. Treatment may be given daily, weekly or monthly and sometimes the time between treatments is tailored to the individual patient. Treatment may be given in cycles which include rest periods where no treatment is given, allowing patients time to build healthy new cells. Some patients are facing life-long treatment. Your Specialist will discuss this with you in detail.

Is chemotherapy expensive?

Treatment of cancer with chemotherapy can be expensive. We use the same drugs used to treat human cancer patients. In addition, your pet will benefit from the expertise of our highly trained oncology Specialists, nurses and support staff, 24 hours a day, 365 days a year. The exact cost of treatment depends upon the type of cancer – the drugs used, the number of treatments, the size of the patient. The projected cost will be discussed with you at your consultation.

Will treatment be covered by my pet insurance?

If you have pet insurance, treatment should be covered, however, you are strongly advised to check your policy carefully before starting therapy and if you have any doubts about your level of cover, you should discuss this with your insurance provider. Payment is expected for each treatment at the time of consultation.

What happens if my pet is sick out of hours?

Southfields Veterinary Specialists is a 24-hour facility and if you have a problem, please call us on 01268 564664 and speak to the duty clinician, who may ask you to bring your pet in. In some cases, we may need to admit your pet for further treatment,  or discharge him/her with medication.

Can I expect any side effects?

Dogs and cats generally tolerate chemotherapy much better than human patients. However, there is the possibility of some side effects. We will always try to provide doses and combinations of drugs that are least likely to cause side effect, whilst achieving the best possible outcome for your pet. Every pet will react differently to treatment and their tolerance will vary. Below are some of the more common side effects:

Vomiting and diarrhoea

The cells of the intestine can be affected by the chemotherapy drugs, resulting in vomiting and diarrhoea. If your pet vomits or has diarrhoea, it will not usually require treatment, however if the vomiting and/or diarrhoea persists for more than 24-36 hours, or if your pet vomits more than 4 – 6 times in a day, please contact us. It may help to withdraw food and water for a few hours, although water should not be restricted for any longer. Once your pet is able to drink without vomiting, you can offer small amounts of bland food such as fish or chicken for a day or so before gradually returning to a more normal diet.

If your pet experiences severe vomiting, it may require hospitalisation and further treatment, including intravenous fluid therapy and drugs to control nausea.

Hair Loss

Most dogs do not lose their hair when receiving chemotherapy, however, breeds with continually growing coats are susceptible (e.g. Old English Sheepdogs, Poodles, some Terriers) and may lose significant amounts of hair. Cats do not usually lose any hair, but may lose their whiskers. Hair will often return when treatment is completed or reduced, but it may take some time for full recovery. A different colour and texture of hair may regrow.


The immune system can be affected by chemotherapy. The cells that fight infection come from the bone marrow and are constantly being replaced. These ‘new’ cells in the bone marrow can be killed by chemotherapy and this can lead to a low white blood cell count, making the patient more vulnerable to infection. This is why blood tests are always checked before we administer more chemotherapy, and if your pet is unwell between treatments and their blood count is low, we will prescribe antibiotics. These infections are rarely serious, but it is important that they are treated immediately.

Will my pet have a normal life whilst undergoing treatment?

This is probably the most important question of all! The goal of chemotherapy is to extend the life of the patient for as long as possible, without compromising the quality of his/her life. If you feel at any point that this goal is not being achieved, please discuss this with your Specialist at the earliest opportunity.

In the majority of cases, the cancers that we treat with chemotherapy are rarely cured but treatment often gives a beloved family member many additional months that they would not have had without treatment.

What happens when treatment is completed?

Once a course of treatment is completed, your Specialist will discuss follow-up appointments for monitoring purposes.

Please observe your pet closely during treatment and telephone us if you feel he/she seems ill or you have any questions or concerns.

Your pet may need to be seen by us or your own vet (or their emergency service) if there are any severe side effects.

Always observe your pet closely during treatment and call us on 01268 564664 if you feel he/she seems ill or you have any concerns.