Few of us have not had our lives touched by cancer. Most of us know someone who has been affected by this disease, be it a family member, a friend, or even a pet. And while cancer is the most common cause of death of cats and dogs, it also the most curable of all chronic diseases. While we tend to associate cancer with serious disease in our pets, not all cancers carry the same prognosis. Many can be cured, long-term remissions can be achieved for others and, for the rest, a good quality of life is possible for a little extra time. Pet Cancer Awareness Month is designed to help owners recognize the signs of cancer early and understand how it is diagnosed and treated.
What is cancer?
All cancers share a common property: the development of new and abnormal tissue (a neoplasm) whose cells have lost the capacity to control their own division. The affected cells grow and divide without control and result in the development of masses (lumps or tumours) or thickening of affected organs. Neoplasia can affect any tissue type in the body.
Benign tumours do not spread to other parts of the body or invade surrounding tissue. Malignant tumours may invade surrounding tissue and can spread to other sites in the body (or ‘metastasize’) via the blood stream or lymphatic vessels. The term cancer is generally used to refer to these malignant growths. Because of their more aggressive and invasive nature, malignant tumours are usually more serious than benign tumours, often causing more extensive disease and may be more difficult to treat. Overall, cats get cancer about half as often as dogs do. But when cats do develop tumours they are much more likely to be malignant. Early detection and treatment are, therefore, essential for the best possible outcome.
What causes cancer?
The cause of cancer in any individual cat is often unknown, and many cancers likely arise for a number of different reasons. Genetic susceptibility to the development of certain tumours almost certainly occurs in cats. The two most common types of cancer found in cats are lymphoma and squamous cell carcinoma. Exposure to environmental factors may trigger abnormalities within cells that may lead to the development of some cancers. This may include exposure to sunlight or to a wide variety of different chemicals (carcinogens). In most individuals the underlying causes and triggers for the cancer remain unknown.
A tumour under a cat’s tongue
We do know that some viral infections in cats can cause cancer, and feline leukemia virus is probably the best example of this. Fortunately, vaccination has helped decrease the incidence of this virus in many areas. However, when susceptible cats are exposed to this virus it can infect the blood-producing cells of the bone marrow and can lead to the development of leukemia or lymphoma. Infection with feline immunodeficiency virus also can lead to the development of cancer. Testing for these viruses is simple and is recommended for at-risk cats.
How would I know if my cat had cancer?
Because cancer is not a single disease, how it affects any one cat will depend on the type of cancer and the region of the body affected. Some cancers grow slowly and initially cause only vague signs of illness such as poor appetite, lack of energy, or weight loss. In other cases there may be more obvious signs such as persistent lumps under the skin or in the mouth, changes in the eyes, vomiting, diarrhea, unexplained bleeding or wounds that do not heal. As the disease progresses, additional complications may develop that relate to the affected tissues or organs.
|Ten Warning Signs of Cancer in Pets|
|1. Lumps and bumps|
|2. Abnormal odours (especially bad breath)|
|3. Abnormal discharges (from the eyes, ears, nose, etc.)|
|4. Wounds that won’t heal|
|5. Unexplained weight loss|
|6. Changes in appetite|
|7. Coughing or difficulty breathing|
|8. Lethargy and depression|
|9. Changes in bathroom habits|
It is important to remember that many other diseases commonly cause the same signs as cancer – especially in older cats. If cancer is diagnosed, there are usually treatment options that will cure, control, or manage the disease, at least for a period of time. As it is important to diagnose cancer early, it is vital to seek veterinary advice as soon as any abnormalities are noticed.
How is cancer diagnosed?
If you or your veterinarian suspect your cat has cancer based on clinical signs and physical exam findings, further testing will be needed to confirm the diagnosis. The diagnosis of cancer can be made only by the microscopic examination of the affected tissue. A biopsy (a small fragment of tissue) is obtained by the veterinarian and sent for microscopic examination for evidence of neoplasia.
X-ray of a cat with a cancerous mass in the chest
Additional tests including radiographs (X-rays) or ultrasound examination of the chest and/or abdomen are often needed to identify the location and extent of the disease and may be recommended prior to any extensive treatment. Blood and urine analyses are performed to determine how the cancer may have affected the patient’s major organ systems and to identify any concurrent disease before treatment is initiated.
With some cancers, occasionally more sophisticated techniques may be required to either make (or confirm) the diagnosis, or to plan the most appropriate treatment. Computed axial tomography (so-called ‘CAT’ or ‘CT’ scans) or magnetic resonance imaging (MRI scans) are becoming more widely available for pets and can be very helpful, especially, for example, in the diagnosis of brain tumours, and in assessing the extent of tumour invasion.
How is cancer treated?
Cancer treatment is as varied as the disease itself. Treatment depends upon the type and extent of the disease, the presence of concurrent disease, and owner finances. Other factors to consider include the patient’s personality and the owner’s ability to provide nursing care at home. Treatments range from simple surgical excision of a benign skin tumour to referral to a veterinary oncologist for therapy involving a combination of surgery, chemotherapy, or radiation of an extensive malignancy.
Cat receiving chemotherapy at our hospital
Cancer treatments should always include provisions for pain control, nutritional support, and prevention of nausea. Many veterinary patients can be successfully treated for cancer but for those cats whose disease is advanced or who cannot be treated for other reasons, hospice care and humane euthanasia provide compassionate alternatives for our feline companions.
[Dr. Glenys Hughes]
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