The ARC Guide to chemotherapy in pets

Is pet chemotherapy the same as human chemotherapy?

No. Our aim for pets is for them to be able to live a normal life throughout their chemotherapy, so the chemotherapy is planned to have as minimal side effects as possible. In humans the aim is often to treat the cancer as aggressively as possible which involves much more intensive chemotherapy treatments, and more frequent and severe side effects.

What is chemotherapy?

Chemotherapy drugs are drugs that are used to kill cancer cells or slow down the growth of a cancer. Some of these are the same drugs used in people with cancer, whilst others have been made specifically for animals with cancer.

• As the main treatment for a cancer, for example cancer of the blood (like lymphoma or leukaemia), where other treatments like surgery and radiotherapy are not possible.
• After surgery has been performed to remove a cancer, if there is a high risk of the cancer regrowing or metastasising (spreading) to other parts of the body (for example haemangiosarcomas or some mast cell tumours).
• Before surgery, to shrink the size of a tumour to make surgical excision possible.
• To slow down the growth of cancers which cannot be treated surgically (for example some thyroid and anal sac tumours).
• In the palliative treatment of some pets with advanced cancer to reduce the discomfort caused by the cancer.

The most common types of chemotherapy are given as a tablet, a quick intravenous injection, or as an intravenous infusion over 10-20 minutes. Tablets may be given in hospital by us, or at home by you, depending on the specific drug and chemotherapy protocol. Intravenous chemotherapies are given through an IV cannula to ensure the drug goes directly into the vein.

How often is the chemotherapy given?

How often your pet needs chemotherapy will be dependent on the drugs and specific chemotherapy protocol being used. This is tailored to the individual pet and differs depending on the cancer being treated and the goals of treatment. Most protocols require chemotherapy to be given in hospital once every 1-3 weeks for a set period of time or number of doses. For some cancers we use protocols that involve chemotherapy tablets administered at home daily or every second day. We will discuss all the different chemotherapy protocol options during your consult, to make sure the protocol works for you and your pet.

How long do pets stay on chemotherapy?

This will depend on your pet’s specific chemotherapy protocol. Most protocols are for a set number of doses (usually 6-16 treatments depending on the cancer type being treated). Occasionally some pets need to stay on chemotherapy longer term or for life.

Our primary goal is for pets to continue to live a normal happy life throughout their treatment. Less than 5% of patients will have side effects that warrant hospitalisation. If any side effects are encountered during treatment that impact your pet’s quality of life, we will always take steps to reduce the risk of side effects happening again in future. We do this by adding in preventative treatments, or by changing the drug, dose or timing of your pet’s chemotherapy.

Because chemotherapy drugs target dividing cells, they do have the potential to cause side effects. We use lower chemotherapy doses in pets compared to human chemotherapy, which means the risk of causing side effects is much lower. Rarely pets can develop severe side effects which can require hospitalisation and these side effects can on rare occasions be life threatening. Please see our chemotherapy side effects sheet for more information.

At each appointment we will give your pet a thorough check over and discuss with you how they have been since their last appointment. Your pet will then be admitted, have a quick blood test performed, and then receive their chemotherapy. Depending on the chemotherapy protocol and your schedule, your pet may stay with us for the day, or the chemotherapy may be given whilst you wait. If an intravenous injection is given your pet will be discharged with a small leg wrap where the IV cannula was placed. This can be removed after 15-30 minutes.

Pets will excrete small amounts of the chemotherapy in their urine, faeces and saliva for a period of time (usually 3-7 days) after each treatment. It is recommended that any people in contact with your pet during this time take common-sense precautions, such as wearing gloves to clean faeces, and not letting your pet lick you, to reduce the risk of absorbing any microscopic contamination that may be in the environment. Certain groups of people, such as pregnant women and small children, should have minimal contact during this period. We will discuss this more and provide an instruction sheet for you to refer to prior to the first dose of chemotherapy.