As with people, dogs often get cancer, especially as they get older. By far the most common areas affected are the skin, the digestive system and the breast, which is the most common in bitches.
The vet says my dog has a tumour – is it cancer?
The language surrounding cancer can be confusing and definitions are difficult. Tumours (also called growths) can be cancerous, or non-cancerous, depending on what they do within the body.
A tumour is the uncontrolled growth of microscopic body components (known as cells). This causes disease, often by forming a lump within the organs of the body and disrupting their normal layout so that they cannot function properly. Some tumours stay in the tissue where they have started; these are generally described as a “benign” and are not actually cancers. Others can spread within the body; these are described as “malignant” and are called cancers.
What causes cancer? Could I have done something to prevent it?
There are some things that appear to make cancer more likely, and statistically, some breeds appear to be more at risk from certain types of cancer. It is known that spaying a bitch before two years of age reduces her risk of breast tumours, but straightforward links with diet and lifestyle have not so far been fully researched in dogs.
What are the symptoms?
Cancer can occur in any part or system of the body and so its symptoms are very varied. Also, many of the symptoms are common to a large range of diseases – so a diagnosis of cancer cannot be made on symptoms alone.
You should certainly take your dog to the vet if you have discovered a lump on the surface of the skin, but not all surface lumps are cancers. A sore that won't heal should also be investigated. Other signs â€¨of tumours (benign or cancerous) affecting internal organs can include:
These can be signs of many other illnesses as well and they are good reasons to take your pet to the vet. Even though cancers may be slow growing, they can sometimes cause sudden signs of illness.
What happens next?
Usually it is not possible for the vet to tell whether an animal has cancer just by looking. Blood tests to screen for cancer are still in their infancy. Further tests, such as blood samples and x-rays, are often needed.
Ultrasound or MRI scanning may be suggested. These may help in discovering whether the cancer has spread to other areas of the body – a process that vets refer to as “staging”. They can also give an indication of your pet’s general health, which affects the ability to withstand treatment.
A biopsy (taking a small sample for examination under a microscope) may help to identify the tumour and see if it is cancerous. Reaching a definite diagnosis can sometimes be difficult; for example, biopsies do not always contain enough good quality material when examined under a microscope.
What is the treatment?
There are many types of tumours and treatment is available for non-cancerous and even for some cancerous tumours. For an isolated lump that has not spread within the body, surgery may provide a cure. But it does depend on where the tumour is growing. Even a benign tumour in an area such as the brain cannot be easily removed in animals. Where a cancer is spreading inwards, the possibilities for treatment depend on the exact type of cancer and how far it has spread. However, quality of life is important and if an animal is in severe, unrelievable pain, your vet is likely to encourage you to choose euthanasia.
There are three basic types of treatment – surgery, chemotherapy and radiotherapy. Several other new therapies are also sometimes available, such as photodynamic therapy or immunotherapy. Some forms of treatment require frequent visits to your own vet, or to specialists, and it can be important for treatment to be given at particular time intervals.
Surgery is often chosen for tumours of the skin, or for internal growths that are apparently distinct. The lump removed at surgery usually needs to be analysed to find out whether or not it is likely to have spread. Sometimes with internal growths where the size of the tumour is causing illness, surgery can relieve the symptoms but the risk of recurrence remains.
Chemotherapy is appropriate for several types of cancer. Veterinary chemotherapy usually has few side effects, or none at all, because the doses used are smaller than those used in humans. Unfortunately, it does not usually cure the cancer – the aim is to slow the cancer down and reduce the symptoms.
Chemotherapy is sometimes carried out following surgery, if it has not been possible to remove the entire cancer, to try to slow down recurrence. It is also used in widespread cancers that cannot be surgically removed, such as those involving the white blood cells (leukaemias). Some types of chemotherapy may be available from your own vet; others are only carried out by specialists.
Regular visits to the vet for treatment are usually essential and sedation may be needed during treatment. You may need to give tablets as well. Possible side effects from chemotherapy include a short period of reduced appetite, vomiting or diarrhoea. Sometimes the drugs will cause the white blood cell count to drop, which can increase the likelihood of infections, so blood tests are usually taken to check for this during treatment.
Radiotherapy is only available at a few specialist centres. Again, it does not usually cure, and regular visits are often needed for a period of time. Because your pet needs to be absolutely still for the treatment, a short general anaesthetic is given for each treatment.
Is it fair to treat an animal with cancer?
Vets are well aware of the importance of keeping animals pain-free and current painkillers are very effective. Sadly, for all animals with an incurable cancer, there will eventually come a point when they are suffering and have lost their quality of life. You and your vet should work together to recognise when this occurs and then opt for euthanasia. However, most vets would agree that a healthy, happy animal does not need to be euthanased even if your dog has an incurable disease.
How long will my pet live?
This is something that cannot be predicted with certainty. The type of cancer and how far it has advanced at diagnosis give some idea, and for some cancers there are more specialised tests that help indicate prognosis. However, like all illnesses, cancers do not necessarily follow a set course. Unfortunately, sudden deteriorations can occur.
Specific types of tumours and cancers
The information given below is not exhaustive, but it gives a general idea of the treatment for the various types of cancer commonly found in dogs.
Many of the lumps that occur in the skin are benign and can be surgically removed. Occasionally, there may be obstacles to removal if the lump is very large, or in an area where repairing a surgical wound is difficult. This is something your veterinary surgeon will discuss. Unfortunately there are some cancerous types that recur in the same place and a few that spread to other sites in the body. Biopsies may be helpful because if an aggressive tumour is identified, then cutting out a larger area of skin at surgery may reduce the likelihood of recurrence or spread.
Dogs have five breasts on each side of the tummy, visible as two rows of nipples, and tumours may occur in one or more. About half of these tumours are benign, while the rest are malignant cancers. The choices for surgery are removal of the lump alone, or removal of some or all of the rest of the breast tissue. Removing more tissue does not appear to prevent internal spread of cancers. These often spread to the lungs, so chest x-rays are advisable prior to surgery, although early spread may not be visible. Spaying a bitch at or after breast surgery could reduce the chance of recurrence.
Leukaemia or lymphoma
This is a cancer that affects the white blood cells. A particular type of white blood cell, called a lymphocyte, is usually involved. Lymphocytes circulate in the blood and also in the lymphatic system, which is a system of vessels and centres (swellings called lymph nodes are often referred to as glands). This is where the body screens for infections and other foreign bodies that may be attempting to enter the system.
When lymphocytes become cancerous, their numbers increase uncontrollably. The lymphocyte count in the blood may rise, but often the lymphocytes sit in one place and multiply. This can cause enlargement of one or more lymph nodes, producing lumps in the throat area or other parts of the body, or it may involve internal organs, such as the liver, spleen or bowel. The cancerous lymphocytes can easily spread to other parts of the body through the blood circulation or the lymphatics (the tubes that connect the lymph nodes).
Because lymphoma is usually widespread, surgery alone is not usually appropriate. Untreated, the average survival time from diagnosis is about two months. This can be prolonged with chemotherapy (in some cases for 12 months or occasionally longer), although unfortunately not all lymphomas respond successfully. Survival expectations are something you should discuss with your veterinary surgeon, as these differ depending on the part of the body affected.
Warning signals that your pet may be in pain
- Changes in behaviour
- Loss of appetite
- Reluctance to move around and go for walks
- Restlessness, difficulty in getting comfortable
- Your pet may seem withdrawn or tense
- An occasional “tail wag” does not mean that your pet is pain free
- An improvement in demeanour with painkillers (only ever give painkillers prescribed by a vet)
For further information, see the leaflet, Time to say goodbye