The thing about cancer in cats
Cats have about half the cancer rate of dogs. But the cancers that cats get are more likely to be malignant.
This combined with the fact that cats tend to hide illness well means that when we find cancer in cats it's often both serious and advanced. That's the thing about cancer in cats.
What is cancer?
All cancers begin with a cell or small group of cells changing abnormally. These abnormal cells then divide and multiply in an uncontrolled way. This may cause a growth called a tumour (lump). Some cancers start from blood cells (eg leukaemia) and these ones don't form solid tumours. Instead the abnormal cells build up in the blood or bone marrow.
The abnormal change in the cell or cells is caused by a gene mutation. This can occur by chance when a cell is dividing or due to damage to the cell. The immune system deals with a lot of these mutations and stops or slows the cancer growth. Some cancers escape the immune system and grow out of control.
Are all tumours cancer?
No. We can have both benign and malignant tumours. A malignant tumour is called a cancer and can spread to other areas of the body (causing secondary or metastatic tumours).
- usually grow pretty slowly
- don't spread to other parts of the body
- are usually covered by normal cells
Benign tumours only cause a problem if they grow very large and become uncomfortable or squash other body parts.
- usually grow quite quickly
- invade surrounding tissues and cause damage
- spread to other areas of the body through the bloodstream or the lymph system
Malignant tumours cause problems in many ways. They can destroy, replace or squash normal tissue causing dysfunction. For example cancer cells growing in the liver can damage liver cells and prevent the liver doing its job; cancer cells growing in the blood vessel walls can result in rupture of the wall and haemorrhage.
The main types of cancer
Cancers are grouped based on the type of cell they start in. There are five main types:
- carcinomas – begin in 'lining' cells such as the skin and tissues that cover internal organs
- sarcomas – begin in connective or supportive tissue cells such as bone, cartilage, fat, muscle or body vessels
- leukaemias – begin in blood forming tissue such as the bone marrow
- lymphomas and myelomas – begin in immune system cells
- brain and spinal cord cancers – begin in central nervous system cells
Cancers are also categorised depending on where they first appear (eg lung cancer, mammary cancer, liver cancer). The most common sites of cancer in cats include: the skin; the immune system (lymphoma and leukaemia); the mouth; the stomach and intestines; and the mammary glands.
Signs and symptoms of cancer
The signs of cancer can be very hard to distinguish from those of other diseases. For example, cats with cancer present with signs such as:
- reduced appetite
- weight loss/muscle loss
- difficulty breathing
- lumps and bumps
- seeming painful
- drinking more/urinating more
- wounds that won't heal
None of these are specific for cancer. If your cat has any of these, get a check up, but don't automatically think the worst!
Cats are very good at hiding illness. It's not unusual for signs to only be noticeable when the cancer is advanced or for us to find something when a cat is brought in for vaccination/check up.
When this happens, it's very distressing and many people feel guilty for not picking things up earlier. The thing about cancer in cats is that there probably wasn't anything you could've detected.
While we might strongly suspect cancer based on history and physical examination, we need diagnostic testing to confirm it.
Going down the diagnostic road isn't right for every patient. Before we do any tests, you need to know about any risks and what to expect from testing.
If diagnostic testing is right for your cat, we'll usually start with general blood and urine testing. We might not get a cancer diagnosis with these, but we can get a good idea of overall health and if other disease are present, which will affect treatment options and prognosis.
When we need more information, we might suggest:
- specific blood tests
- diagnostic imaging (ultrasound or X-ray)
- tissue sampling (needle aspirates or biopsies)
A pathologist can look at the samples and hopefully give us a specific diagnosis.
Some areas of the body are hard to get information about. A prime example is the brain, which we can only see with a CT or MRI.
When cancer is diagnosed, we may also need to 'stage' it. This means working out if and how far it's spread.
Treatment for cancer in cats
The best treatment will depend on the type of cancer, where the cancer is and the overall health of your cat. It also depends on you and your situation. Going forward with cancer treatment can be a roller coaster ride with many up days and down days. And it's important to acknowledge that sometimes no treatment is a good option.
Cancer may be treated with surgery, chemotherapy or radiation. Often a combination of treatments is used. Let's look at these a bit more.
For most of the cancers we see in cats, if we're going to get a cure, it's going to be achieved by surgery. The 'best' types of cancers are the ones we can cut out.
Unfortunately, many cat cancers are not operable. They've either spread or they're not in a place we can operate on (eg in both kidneys) or surgery might reduce quality of life too much (eg removing the tongue).
We do a lot of cancer surgery, but there will be some that we'll suggest you see a specialist surgeon for.
Chemotherapy ('chemo') is widely used to treat cancers in cats. It's important to know that chemo aims to put cancer into remission – hopefully for years – but it's not a cure.
Different cancers require different chemo protocols. Different cancers also have different remission periods. With cats, we consider a 'long' remission to be more than a year.
Naturally, we all tend to think about what happens to people having chemo, especially losing hair and feeling sick. If it's any consolation, cats only occasionally lose their whiskers but they don't go bald and they don't usually feel persistently sick. Compared to people (and dogs), cats generally handle chemo pretty well. In a study of people's perceptions of the quality of their cat's life during chemo, 83% were happy they decided to try chemo treatment.
We can do chemo at Elwood, but we're not cancer specialists (oncologists). There are some very good oncologists in Melbourne that we can refer you to if needed.
Radiation can be a very effective cancer treatment in cats. This is especially the case where the cancer is confined to one area but can't all be removed surgically (eg tumours of the face/mouth). The side effects of radiation are generally not too bad, but a general anaesthetic is needed to give each treatment.
Radiation is only available at a few specialist centres in Australia. Fortunately, we do have one quite close to us – SouthPaws in Moorabbin.
There are three commandments when it comes to palliative care for pets:
- don't let them be in pain
- don't let them be miserable with nausea and vomiting (and diarrhoea)
- don't let them starve
We'll often try to preempt these problems, especially pain, by providing medications before obvious signs occur.
Just as important as sticking to these commandments is making sure anything we prescribe is able to be given easily and with the minimum of stress (to you and your cat). If you can't give medications, please tell us – there's no judgement here!
Caring for the carer
It's normal to feel a whole range of emotions when caring for a pet with cancer: sadness, grief, anxiety, fear, uncertain, guilt, stress and a lot of love. Make sure you acknowledge your feelings and take care of yourself – your cat needs you to be okay.
While we're trained to treat pets, we're people who talk to people all day. You can talk to us. We have a lot of tissues available.
Specific cat cancers
Lymphoma (lymphosarcoma, LSA) is the most common cancer in cats (about 25% of all cancers). It starts in lymphocytes, which are cells of the immune system that make antibodies. These cells are both in the blood and within body tissues.
Because lymphocytes are widely distributed in the body, lymphoma can occur in virtually any organ (eg liver, spleen, kidneys) or tissue (eg lymph nodes, eyes). But the gastrointestinal (alimentary) form of lymphoma is the most common and accounts for about 80% of cases.
Unfortunately, the gastrointestinal form tends to have very vague symptoms (weight loss, inappetence, vomiting and sometimes diarrhoea), which are the same as with conditions such as inflammatory bowel disease and pancreatitis. The gastrointestinal form can be very hard to detect on physical examination as the cancer cells are within the gut wall and can't be easily felt. Ultrasound is very useful for detecting lymphoma.
Chemo is the most commonly used treatment and can lead to complete remission rates of approximately 30–65% with a median duration of remission of 3–7 months. Cats with feline immunodeficiency virus (FIV) tend to have a poorer prognosis.
Squamous cell carcinoma
Squamous cell carcinoma (SCC) is a skin cancer that frequently occurs on the ears and nose of cats with white or light coat colours with little pigmentation. It occurs in these areas due to chronic sun damage. Even though SCC is a skin cancer, it can also develop in the oral cavity of cats. This suggests that sun exposure isn't the only cause.
The treatment of choice is surgery (eg ear amputation). But oral and nasal surgery is very complicated in cats, so radiation therapy may be used as well as or instead of surgery. Chemo is typically unsuccessful.
Palliative treatment with pain medication and anti-inflammatories can result in a good quality of life for quite long periods.