Cancer: What You Need to Know

In 2006, Regan, an 11-year-old cocker spaniel, was visiting the veterinary hospital for a routine senior wellness exam. During the exam, his veterinarian detected a small mass in the left anal sac. Preanesthetic blood tests, x-rays, and an ultrasound showed nothing abnormal. The tumor was removed and a biopsy performed, and it was found to be a carcinoma with histologically complete margins (a clear zone of normal tissue around the borders of the tumor). Regan recovered well from surgery. No further treatment was prescribed, and the dog is doing well nearly two years later, with no evidence of cancer.

Cancer is one of the most frightening diagnoses pet owners hope they never hear. Although it can't always be cured, the good news is that cancer is considered a chronic disease, which means it can be successfully controlled in many cases. In addition, the earlier the disease is detected, the better the chance of remission or cure. Regular wellness examinations and routine screening are crucial to detecting cancer as early as possible.

WHAT IS CANCER, AND WHAT CAUSES IT?

Cancer is the process in which normal cells in the body undergo excessive or uncontrolled growth. Cancer can occur in any organ in the body and can spread from one part of the body to another through the blood or lymph system; this process is called metastasis.

Cancer is caused by a variety of factors, potentially involving viruses, genetic components, exposure to carcinogens, and other unknown causes. In this respect, cancer in pets is the same as in any other animal, including humans. Some cancers in pets are preventable, such as breast (mammary) cancer in dogs, which rarely occurs after early spaying or neutering.

Cancer is not contagious. With the exception of canine transmissible venereal tumor, which can spread to other dogs, there is no evidence that cancer can spread to other animals or to their human caregivers. In cats, some cancers are associated with feline leukemia virus, which is a contagious virus that can pass between cats, but the cancers themselves are not contagious.

The longer a cancer goes untreated, the greater the chances are for it to compromise your pet's quality of life. Other organs may become affected (through metastasis), and the function of normal cells may be compromised. In addition, secondary effects of the cancer can cause acute, life-threatening problems.

Many of the signs of cancer (see the box on page 27) are nonspecific, indicating problems that could be caused by another condition or disease, so a visit to your primary care veterinarian is always the first step when you suspect something amiss in your pet.

WHAT HAPPENS AFTER CANCER IS DIAGNOSED?

If a cancer diagnosis is confirmed, your veterinarian may suggest a biopsy (if one hasn't already been done), lymph node evaluation, x-rays, standard blood tests, and a urinalysis, as well as more complicated procedures. These procedures are performed to determine the pet's general health, the stage of the cancer, and possible treatment strategies. Ask your veterinarian if you have any questions about these procedures.

The treatment of cancer in pets has evolved to parallel treatment in humans, with certain differences. One of the most important differences is in the goal of therapy. In humans, many cancers are cured, and cancer survivors may enjoy many decades of comfortable life. For this reason, treatment of cancer in humans is aggressive and often associated with severe side effects. On the other hand, most pet owners prefer to avoid severe side effects and prolonged hospitalization for quality-of-life reasons. In addition, the intense, specialized supportive care units and strategies for human cancer patients are not available for pets. Therapies are therefore often primarily directed at maximizing quality of life, and the aim is usually tumor control, or remission, rather than cure at any cost.

It is important to recognize that although your pet's cancer may not be curable, he or she can enjoy a high quality of life. In this sense, cancer is similar to other chronic illnesses such as kidney or heart disease.

More than one form of treatment is often required to effectively fight cancer. This can mean using as many as three different cancer therapies, including surgery, radiation therapy, and chemotherapy, in addition to complementary treatments, diet, and supportive care. Such an approach requires a multidisciplinary cancer care team that develops, coordinates, and monitors all aspects of your pet's treatment plan.

THE CANCER CARE TEAM

One of the most influential factors affecting your pet's quality of life and remission time is the dedication that you and your veterinary healthcare team have. As your pet's primary caregiver, you are in the best position to know and meet your pet's needs. Your most important task is to find a veterinary team that is experienced in cancer treatment and committed to working with you as a member of that team to provide cutting-edge treatment and compassionate care.

Start with Your Primary Care Veterinarian

Your primary care veterinarian plays an essential role on the cancer care team. He or she is familiar with your pet's medical history and can serve as his or her “care ambassador.”

Careful evaluation of each pet is necessary to plan the best treatment. Your veterinarian will perform a thorough physical examination and a review of medical records, x-rays, blood tests, and other test results. Sometimes additional testing is necessary. Your veterinarian will discuss your pet's individual situation with you in detail and will work with you to formulate a treatment plan. 

Tip: It's crucial that all members of your pet's veterinary 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.

Involve Specialists If Needed

Although your primary care veterinarian is an integral part of the cancer care for your pet, you may need to visit a specialist in veterinary oncology. These board-certified veterinarians have undertaken further training and have achieved certification in cancer diagnosis and treatment. Specialist veterinarians will not only assist you in making the best treatment decisions for your pet but will also work to support the relationship between you as the owner/caregiver and your veterinarian.

Your pet's veterinary healthcare team may include a veterinary oncologist, a veterinary radiation oncologist, or a veterinary surgeon who has considerable experience in treating cancer in pets. Depending on the type of cancer, all three specialists may be involved in decision making and working with you and your primary veterinarian to coordinate the best possible treatment for your pet while maintaining your pet's best quality of life.

Veterinary oncologists believe that any pet with cancer can be helped. That help may include treatment using traditional and nontraditional means, or it may involve palliation (relief or lessening of symptoms) to maintain quality of life. Regardless, the only way to make the best decision for your pet is to have access to the best, most up-to-date information and advice possible.

HOW IS MY PET LIKELY TO RESPOND TO TREATMENT?

For cancer in dogs and cats, expected remission times and life span, or “prognosis,” are highly variable and depend on a number of factors, the most important of which is the type of cancer, diagnosed by a biopsy. Other factors that influence your pet's prognosis include:

• The stage of the disease, which reflects the number, location, and size of tumors in the body
• Whether your pet is feeling sick or not (loss of appetite is one of the most important symptoms)
• Histologic grading, which is the specific appearance of tumor cells and their pattern of infiltration in various tissues (what pathologists find when they examine a biopsy specimen)
• The presence of paraneoplastic syndromes (tumor-associated conditions)
• The treatment chosen and the care given by the owner and veterinary team
• The pet's response to therapy

It's difficult to accurately predict the prognosis for individual pets because not enough is known about the specific way the above factors influence prognosis for the wide variety of cancers that occur. However, in general, pets who are not feeling sick and are diagnosed early in the course of tumor growth have a better chance of remission with treatment. Some animals are truly cured of cancer, but this depends greatly on cancer type.

Pets who are not feeling sick and who are diagnosed early generally have a better chance of remission with treatment.

By taking your pet to your veterinarian for regular visits and routine screening—as well as any time you suspect something might not be quite right—you give your pet the best chance of living a longer, more comfortable life.

What to Watch For

The signs of cancer depend both on the type of cancer and where in the body it is located. Signs may include:

• A mass on the pet's body
• Enlarged lymph nodes
• Reduced appetite
• Less energy
• Changes in bowel movements
• Unusual odor from the mouth

None of these signs is absolutely diagnostic for cancer, but any of them signals that a veterinarian should be consulted to examine your pet and decide if further testing is needed.

Routine Screening Is Essential

Some cancers occur more often in certain breeds. For example, a British study found that English cocker spaniels were 7.3 times more likely than other breeds to develop an anal sac carcinoma, like Regan had. In addition, some cancers are seen more often in older dogs. However, cancers can affect pets of any age. This is why routine screening is important for dogs and cats (as it is for early detection of breast or prostate cancer in humans). Screening allows early diagnosis and potentially curative treatment.

Taking your pet to see your veterinarian is crucial as soon as you suspect a problem.

When seeing a veterinarian (such as a specialist) 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 of a particular problem, be sure to provide a history of events, recurrences, treatments, medications, and outcomes associated with the condition(s). A written list can save time and ensure completeness.