Q: Please provide a review on pallia-tive care for animals diagnosed with cancer.
A: Dr. Dennis Bailey gave an excellent lecture on Palliative Care for Cancer Patients at the 2008 American College of Veterinary
Internal Medicine Forum in San Antonio. Here are some relevant points:
Neoplasia still remains one of the most common causes of death and euthanasia in dogs and cats. For seve-ral common forms
of cancer, such as lymphoma and osteosarcoma, aggressive treatment consistently provides extended periods of excellent quality
of life but only rarely provides a cure.
Many dogs and cats diagnosed with cancer never undergo definitive cancer therapy, either because they are not good candidates
or because of owner choice. For these animals, palliative care is important to provide and sustain an excellent quality of
life for as long as possible.
It is important to recognize that a treatment is defined as palliative care or definitive therapy based on the intended outcome,
not the actual outcome.
Palliative care refers to supportive care given to improve or maintain quality of life, without necessarily slowing the progression
of the cancer or prolonging life. In contrast, definitive therapy refers to aggressive treatment administered with the goal
of trying to slow cancer progression and prolong life.
Palliative care should not be regarded as "giving up." Some dogs and cats with advanced-stage cancers do not benefit from
more aggressive definitive-intent therapy. For example, when dogs with metastatic osteosarcoma are treated with definitive-intent
therapy, survival times are compar-able to those achieved with palliative care alone. Conversely, palliative care should not
be regarded as "enabling the owner to prolong the inevitable." If an animal's quality of life is suboptimal and cannot be
restored with palliative care, then humane euthanasia should be recom-mended. However, palliative care often is very effective
at restoring quality of life or prolonging excellent quality of life. Additionally, whenever palliative care is being provided,
close owner communication is essential to ensure that quality of life is being maintained.
Malnutrition is a common complication of cancer. A recent veterinary study indicated that, while only 4 percent of dogs with
cancer were emaciated — defined as body conditioning score <3 out of 9 — at the time of initial diagnosis, 68 percent had
documented evidence of weight loss and 15 percent had moderate to severe muscle wasting. Cancer cachexia is a complex metabolic
syndrome characterized by weight loss, anorexia and wasting of lean body mass secondary to the growing malignancy.
The factors contributing to cancer cachexia can be divided into two broad categories. The first includes mechanical and functional
abnormalities that lead to decreased nutrient intake.
Oral tumors can cause dysphagia and considerable pain. Gastrointestinal tumors can cause pain, early satiety, mechanical obstruction,
nausea, vomiting, diarrhea and malabsorption of nutrients. Advanced-stage neoplasia, regardless of its anatomic location,
often is associated with partial or complete anorexia.
The second group of factors includes numerous metabolic derangements that prevent the body from efficiently using nutrients.
Abnormalities in the way the body uses carbohydrates, proteins and lipids all have been identified. The result is that a cancer
patient can lose weight and lean muscle mass even in the face of adequate food intake. The underlying mechanisms for these
metabolic derangements are not completely understood, but substances released by the tumor itself and by the patient's body
in response to the tumor are both thought to play important roles.
An animal's nutritional assessment is based on a thorough history and physical examination. It is important to ask an owner
about his or her animal's usual dietary habits, including the type of food, the amount fed at each meal, the number of meals
per day, the types and amounts of treats given and the extent of the animal's appetite.
The owner should then be asked about any recent changes in dietary habits, as well as any changes in body weight or body conditioning.
Physical examination should then be used to assess weight, body condition and muscle mass objectively. If available in the
medical record, previous assessments should be used as a baseline for comparison.
Early changes associated with cancer cachexia may be as subtle as the animal not finishing its food as quickly as usual or
requiring some coaxing. As cancer cachexia progresses, the animal's nutritional intake will become inadequate despite coaxing
and offering more palatable foods, and eventually weight loss and muscle wasting will become evident.