What is cancer?
Cancer is the process where normal cells in the body undergo excessive or unrestrained growth.
Cancer can occur in any bodily organ and can travel from one part of the body to another distant part by the blood or lymph system. There are more than 100 different types of cancer that can be grouped into one of six major categories:
Sarcomas: Cancer that begins in tissue that connects, supports or surrounds other tissues and organs (such as muscle, bone and fibrous tissue).
Carcinomas: Cancer cells that originate in tissues that cover a body surface, line a body cavity or make up an organ.
Lymphomas: Cancer that occurs in cells that make up an important component of the immune system and protect the body's cells.
Leukaemias: Cancer that occurs in the blood-forming tissues and blood cells.
Skin cancers: Cancer that originates in the skin cells; the most common in dogs being mast cell tumour.
Brain tumours: Cancer that originates in the brain cells.
What are the causes of cancer in a pet?
Cancer is caused by a variety of factors, potentially involving viruses, genetic components, exposure to carcinogens, and other unknown factors. In this respect cancer in pets is the same as in any other animal, including humans.
What should I do?
Try as you might, when you hear the word "malignant," it's hard to focus on anything but what it may mean for your pet. What are the treatment options? What will work? How will having cancer affect your pet’s quality of life?
First, most cancers require more than one form of treatment to effectively fight the disease. This can mean using as many as four different cancer therapies, including Surgery (surgical oncology), Chemotherapy (medical oncology), Radiation therapy (radiation oncology), and immunotherapy. This requires a multi-disciplined cancer care team that develops, coordinates and monitors all aspects of your pet’s treatment plan.
Start with a primary care veterinarian.
Primary care is a term for the branch of medicine concerned with your pet’s overall, general well being. It is important to have a veterinarian who is familiar with your pet’s medical history and who can serve as their "care ambassador".
Know your pet’s medical history.
Particularly when seeing a veterinarian for the first time, it's important to give a complete picture of the health status of your pet. If your pet has several health problems or a long history with one, be sure to provide a history of events, recurrences, treatments, medications, and outcomes associated with the condition. A written list can save time and ensure completeness.
Make sure all members of the cancer care team are informed.
If your pet develops a condition that requires one or more specialists or needs surgery, it's important that all members of your pet’s veterinary medical team have complete and consistent information. So when you visit one veterinarian, make sure you have the names and contact numbers of any others involved with your pet’s care and keep them apprised of your pet’s condition.
Know when and how you will receive test results.
Assume nothing. Ask when and how you will be notified of test results. If results do not arrive when you expect them, contact your veterinarian and ask about them.
Specialist veterinary care
Although your primary care veterinarian is an integral part of the cancer care for your pet, often you may need to visit an expert in a specific area of veterinary science. These veterinarians have undertaken further training and have achieved certification by various veterinary Colleges. They are often called Specialists.
Medical oncology is the general study and treatment of cancer. Medical oncologists are trained in the prevention, detection and medical treatment of all forms of cancer.
Surgical oncology is the specialty concerned with the physical removal of cancerous tissue. Sometimes, surgery is augmented with other forms of care, such as chemotherapy or radiation therapy. Surgical oncologists have specialty experience in treating distinct types of cancer, from breast, bone and lung cancer to cancers that occur within the abdomen, as well as skin cancer.
Internal medicine deals with the function of the internal organs, such as the liver and lungs, plus the diagnosis and treatment of associated problems. Internists often provide the first contact for an unspecified internal illness or problem. They may diagnose and treat the problem themselves, or work in conjunction with another specialist (such as an oncologist) for more focused diagnosis and treatment.
Emergency medicine is the specialty that deals with critical health and accident cases, where immediate treatment can sometimes mean the difference between life and death.
How is my pet likely to respond to treatment for cancer?
For cancer in dogs and cats, expected remission times and life span, or "prognosis", is highly variable and depends on a number of factors, the most important of which is the type of cancer as diagnosed by biopsy. Other factors that will influence your pet’s prognosis include:
- The stage of the disease, which reflects the number, location, and size of major populations of tumour cells in the body.
- Whether your pet is feeling sick or not. Loss of appetite is one of the most important symptoms.
- Histologic grading: the specific appearance of tumour cells and their pattern of infiltration in various tissues (what the pathologists reports from a biopsy specimen).
- The pet’s response to therapy.
- The presence of paraneoplastic syndromes, previously described.
- The treatment chosen and the care given by the owner and veterinarian.
It is difficult at this time in veterinary medicine to accurately predict the prognosis for a given individual pet because not enough is known about the specific way the above factors influence prognosis for the wide variety of cancers that occur.
In general, pets that are not feeling sick and are diagnosed early in the course of tumour growth have a better chance of remission with treatment. Untreated pets with malignant cancer often live 2 months or less, but this varies greatly depending on the type of tumour. Lymphoma and osteosarcoma are two common cancers in dogs. With therapy, many dogs with one of these cancers live 9 months to 1 year. Therefore, a reasonable goal is a 1 year survival. Occasionally the pet will live much longer, up to 2 1/2 years or more. Some animals are truly cured of cancer, but this depends greatly on the tumour type.
The treatment of cancer has evolved over the last few decades to parallel treatment in humans, with certain differences. The important difference between cancer therapy in humans, and that offered for pet animals, is in the goals of therapy. In humans, many cancers are cured, and cancer survivors may enjoy many decades of comfortable life. For this reason, treatment of cancer is aggressive and may be associated with side effects. While pet animals are very similar biologically to humans, the chance for survival of decades is remote. Therapies are therefore directed at preserving quality of life; and tumour control, or remission, is the aim rather than cure at any cost.
The goal of veterinary cancer therapy is to achieve a "complete clinical remission" or to make the pet as normal as possible with no outward evidence of cancer. Often the treatment starts with surgery. If the surgeon is unable to remove all the tumour cells without causing compromise to your pet’s quality of life, then radiation therapy may be offered as a follow-up. If the tumour has spread to other sites, or if the risk of spread is very high, then treatment may involve the use of anti-cancer chemotherapy medications. They are used in a set format, or "protocol". Various such protocols exist, using slightly different drug sequences and dosages.
It is important to recognize that although cancer is a rarely curable disease, your pet can be treated in such a way that a high quality of life is achieved following diagnosis. In this respect, it is similar to treating heart or kidney disease, which can also be fatal. Remember that one of the most important factors influencing your pet’s quality of life and remission time is the interest and dedication of you and your veterinary care team.