Animals can suffer from many different types of cancer; fortunately a fair proportion of these cancers will respond to treatment. As Veterinary Surgeons we have many treatment options available to us and these options include drug therapy, which we call chemotherapy. We use chemotherapy in different ways depending on the type of cancer we are treating. Sometimes we use drug therapy alone, sometimes it is used before surgery to reduce the size of a tumour and sometimes it is used after surgery or in combination with radiotherapy to help prevent recurrence or distant spread (metastasis).
The thought of giving your pet chemotherapy can be worrying and deciding whether to start therapy can be very difficult. The mention of chemotherapy may bring thoughts or memories of people being very ill for long periods as a result of their treatment. In veterinary medicine we do not usually make animals unwell as a result of their chemotherapy. This is because we are trying to make them as well as possible, for as long as possible, rather then giving treatments that will adversely affect their quality of life. We would expect animals to have normal quality of life through their treatment with chemotherapy and for your pet to be a part of family life as usual.
Unfortunately chemotherapy can cause some side effects and this is a result of the way chemotherapy drugs work. Cancerous cells divide very quickly, so treatment is aimed at trying to slow down tumour growth and kill cancerous cells. As a consequence other cells in the body that divide quickly can be affected. The cells that we most worry about are in the bone marrow and in the gut, as they turnover very quickly. The bone marrow produces new red blood cells (which carry oxygen to the tissues), white blood cells (which fight infection) and platelets (which help the blood to clot). Chemotherapy will slightly reduce the production of both white blood cells and platelets as they turnover in the body very quickly. However red blood cell production is rarely affected by chemotherapy as they have a much longer lifespan in the body. The reduction in white blood cells and platelets as a result of chemotherapy is rarely a clinical problem, however it is important that we check that the white blood cell and platelet numbers have returned to normal, before further chemotherapy is given. If they have not then white blood cells may fall to a dangerously low level leading to infection and low platelets may lead to bleeding problems. Cells in the gut are also affected by chemotherapy, which is why transient nausea, vomiting and diarrhoea can be seen after chemotherapy administration. Animals rarely lose their hair as a direct consequence of chemotherapy, but poor hair re-growth over clipped patches is relatively common and cats can occasionally lose their whiskers.
Every care will be taken to reduce the risk of side effects to an absolute minimum. Depending on the type of chemotherapy given, we would expect to see side effects in about 10% of our patients. When side effects do occur they are usually mild and self-limiting, with the most common side effects being transient nausea, vomiting or diarrhoea after the chemotherapy has been given. Rarely some animals will become very sick and then need hospital treatment. If side effects do occur there are many ways we can adjust chemotherapy protocols and adjunctive treatments that we can give that will reduce the likelihood of them happening in the future.
Chemotherapy drugs do represent a small amount of risk to the people handling them, which is why we will prepare and administer the drugs using our specialist equipment and expertise at Dick White Referrals. If you are given chemotherapy drugs to administer at home this will be fully explained to you during the consultation; however gloves should be worn whenever chemotherapy drugs are handled.
After your pet has received chemotherapy, the drugs given are excreted in a form that is still active. There are minimal risks as a result of this if sensible precautions are observed. However if you, or anyone in contact with your pet is pregnant, immunosuppressed or has very young children, there is an increased risk and you should discuss this fully before chemotherapy is commenced. Chemotherapy drugs are excreted in urine and faeces, so these represent the main risk of exposure in the 3-5 days after they have been given. If your dog urinates normally outside this represents little risk, however gloves should be worn when handling bags used to collect faeces and when cleaning cat litter trays. If an accident occurs inside (vomit/urine/faeces) in the first 3-5 days then it needs to be cleared up carefully, again this will be discussed with you in more detail once treatment is underway.
There is a lot to consider before commencing treatment with chemotherapy, which we will fully discuss with you during your consultation. How successful chemotherapy will be depends on the type of tumour present and needs careful assessment of each individual patient, the likely outcomes will be explained in detail before treatment is commenced.
