What is cancer?
Cancer refers to a group of diseases in which abnormal cells (the structural and functional units of all living organisms)
grow without control, invade surrounding tissues and ultimately spread to other organs throughout the body. Caring for
pets diagnosed with cancer will require not only a well trained and dedicated veterinary team who understands both the
medical and emotional aspect of cancer but also a well informed pet owner who actively participates in the treatment

There are over a hundred specific
cancer types, each behaving in a unique way and requiring unique treatment
. Besides treating the cancer itself, other very important aspects of cancer management include pain control
and nutrition. It is imperative that pets with cancer are provided with pain medication to relieve discomfort caused by the
disease as well as by the treatments, and are fed diets specifically designed to support a cancer patient. To learn more
about these topics, please visit the
Cancer Pain Management and Cancer Nutrition sections.

How does cancer form in cats and dogs?
In a normal body, new cells are constantly being made to replace old or damaged cells. This process is tightly regulated
and a delicate balance exists between cell multiplication (division) and cell death to maintain the right number of cells.
Sometimes this process goes wrong because of changes in the cell's genetic material (DNA), and the body begins to
produce more cells than it needs and/or cells don't die when they should. These extra cells usually undergo further
genetic changes and can then form a mass called a tumor.  

Tumors can be either benign (noncancerous) or malignant (cancerous). Benign tumors typically remain localized to one
place and do not invade surrounding tissues or distant organs. They are not usually dangerous but can cause medical
problems once their size begins to compress on surrounding tissues. In contrast, malignant tumors contain cells that have
the ability to invade neighboring tissues and to spread to distant organs via blood circulation or the
lymphatic system, a
process known as metastasis. To learn more about metastasis, please visit the
How Does Cancer Spread section.

Is cancer contagious?
Cancer is NOT contagious. Feline leukemia virus, which causes certain types of cancer in cats, is the only exception.
While this virus can spread between cats, it cannot be passed on from a cat to a dog or to a human.

Can cancer be treated in cats and dogs?
Similarly to humans, cancer is the leading cause of death among older cats and dogs, and accounts for approximately
50% of deaths each year. However, cancer should not be automatically equated with a death sentence because it can be
successfully treated if diagnosed early. Several treatment options are available for your pet, including
chemotherapy, radiation therapy, immunotherapy, targeted therapy, cancer vaccines and others. To learn about which of
these treatment options are used to treat your pet's specific cancer, please visit the "
Cancer Types in Cats and Dogs"

Even if your pet is diagnosed with cancer for which there is no effective treatment or your pet did not respond well to a
traditional treatment, enrolling your pet in a veterinary clinical trial may provide you with an option to try new therapies.
The treatment is often available at decreased or no cost to you and even if your pet did not respond to the new
investigational therapy, its participation will help scientists develop better and more successful cancer treatments in the
future. To learn more about these trials (which are partially or fully funded by the institutions), please visit the
Dog Clinical
Trials or Cat Clinical Trials sections. To learn more about veterinary clinical trials in general, please visit the Pet Clinical
Trials section.

Does cancer cause pain in pets?
Pain is common in pets with cancer, with some tumors causing more pain than others. In addition to pain caused by the
actual tumors, pets will also experience pain associated with cancer treatments such as surgery, radiation therapy or
chemotherapy. Untreated pain decreases the pet's quality of life, and prolongs recovery from the illness, treatment or
injury. It is, therefore, essential that veterinary teams that are taking care of pets with cancer should also play a vital role
in educating pet owners about recognizing and managing pain in their pets. The best way to manage cancer pain in pets
is to prevent it, a term referred to as preemptive pain management. This strategy anticipates pain ahead of time and
administers pain medication before the pet actually experiences pain, thus ensuring the pet's maximum comfort.

To learn more about which tumors are likely to cause a lot of pain, how to recognize pain in pets with cancer and what
cancer pain management options are available for your pet, please visit the
Cancer Pain Management section.

Is nutritional support important for pets with cancer?
Cancer cachexia (a term referring to progressive severe weight loss) is frequently observed in pets with cancer. Pets with
cancer lose weight partly because of lack of appetite and partly because of cancer-induced altered metabolism. Some of
the causes for decreased appetite are related to the cancer itself (for example, tumors may physically interfere with food
chewing, swallowing, and digestion process) and some may be related to the side effects of cancer treatment (for
example, some chemotherapy drugs cause nausea and vomiting, and radiation therapy can cause mouth inflammation).

Proper nutrition while undergoing cancer treatment is essential to maintain your pet's strength, improve survival times,
quality of life and maximize response to therapy. Adequate nutritional support was shown to decrease the duration of
hospitalization, reduce post-surgery complications and enhance the healing process. Additionally, pets with cancer need
to be fed diets specifically designed to provide maximum benefit and nutritional support for the patient. To learn more,
please visit the
Cancer Nutrition section.

Who treats cancer in pets?
The medical science that studies cancer in animals is called veterinary oncology and veterinarians that specialize in
cancer diagnosis and treatment are called veterinary oncologists. Veterinarians that perform surgery to treat cancer are
called veterinary surgical oncologists and those who administer radiation treatment are called veterinary radiation

Where do I find a qualified veterinary oncologist?
To locate a qualified veterinary oncologist worldwide who can discuss with you appropriate cancer treatment plan for your
pet's cancer condition, please visit the "
Locate a veterinary oncologist" section.  

How common is cancer in cats and dogs?
Cancer occurrence rate is usually measured as the number of new cases of cancer in companion animals per year. The
rates are difficult to calculate because there are no registries in place and the following numbers represent only
approximate yearly cancer incidence in dogs and cats per 100,000 animals based on available data:

Source: Withrow Stephen J, and David M. Vail. Small Animal Clinical Oncology. St Louis: Saunders Elsevier, 2007.
Tumor formation through loss of normal growth control
Metastasis of malignant tumor cells
Cancer site
Overall cancer occurrence
Skin (nonmelanoma) cancer occurrence
Skin (melanoma) cancer occurrence
No Data
Digestive cancer occurrence
Respiratory cancer occurrence
Connective tissue cancer occurrence
Mouth and pharynx cancer occurrence
Breast cancer occurrence
Lymphoid tumors occurrence
Bone cancer occurrence
© 2007 Pet Cancer Center. ALL RIGHTS RESERVED.
Last updated 2/19/2017
Comprehensive guide to cancer diagnosis and treatment in cats and dogs
What is cancer?
Introduction to cancer in cats and dogs