Therapeutic modalities: adjunctive therapy
Adjunctive therapies have long been used as a means of improving the quality of life in veterinary cancer patients and are now an accepted component of oncology case management. Because the quality of their pet’s life is usually the owner’s first concern, decisions on primary and adjunctive therapies should not only consider disease factors but also the owner’s goals, preferences, and limitations.
A variety of adjunctive therapies are employed in controlling the clinical signs encountered in dogs and cats that are treated for cancer. A treatment goal for any oncology patient is to maintain quality of life by limiting treatment side effects, pain, and discomfort. Clinical signs may be caused by the cancer itself, such as the pain associated with osteosarcoma or may be a side effect associated with a treatment modality, such as radiation or chemotherapy.
Side effects associated with chemotherapeutic agents include vomiting, nausea, anorexia, diarrhea, hair loss, and bone marrow suppression. Although nausea and vomiting are often self-limiting in oncology patients, in some cases they are severe enough to require medical intervention. Fortunately, there are a variety of anti-emetics available today. Metoclopramide has been used for decades in veterinary medicine and is an effective anti-emetic. Maropitant citrate,e a newer NK1 receptor antagonist, is gaining in popularity due to its efficacy and the convenience of oral or injectable once daily dosing. A recent study revealed that the use of maropitant citratee for five days following doxorubicin administration significantly decreased the amount and intensity of vomiting.14 Ondansetron hydrochloridef and dolasetron mesylateg both 5-HT3 receptor antagonists, may also be used to control vomiting. Some advocate the addition of an H2 blocker (famotidine) or proton pump inhibitor (omeprazole) to minimize the risks of vomiting and reflux esophagitis. Diarrhea following chemotherapy administration has also been reported and is often easily managed with metronidazole or opiate antidiarrheals, such as loperamide.
Anorexia attributed to chemotherapy has been reported in oncology patients as well. The most common cause of anorexia is nausea, but occasionally another underlying disease process may be responsible for gastrointestinal signs and should be considered. Appetite stimulants, such as mirtazapine, a 5-HT3 receptor antagonist, or cyproheptadine, a serotonin antagonist antihistamine, have been used with some success in canine and feline oncology patients. Some veterinarians will dispense medications for owners to have at home and use on an as-needed basis, for example the “3-Ms” of maropitant citratee (or metoclopramide), metronidazole, and mirtazapine. Some clinicians, on the other hand, prescribe medications only at the occurrence of clinical signs. Inmost cases, clinical side effects of chemotherapy are self-limiting or can be managed with owner-administered medications. However, chemotherapy side effects should never be considered trivial. In some cases, they are life threatening and require hospitalization for more intensive treatment.
The nutritional status of all oncology patients should be routinely assessed beginning at diagnosis and throughout treatment. The incidence of cachexia is lowin veterinary patients. It is characterized by a distinct set of metabolic changes that are nearly impossible to reverse once they are present, although dietary modifications can slow progression. Diets should be tailored to each individual taking into account their cancer diagnosis, any other disease processes (e.g., pancreatitis or renal disease), and nutritional needs, as well as environmental factors including other pets in the household and an owner’s ability or willingness to feed the diet. The most important dietary consideration for canine and feline oncology patients is that the ration is palatable and eaten, otherwise it has no benefit. Providing a complete and balanced diet, whether commercially available or homemade, is imperative. A variety of diets have been used for veterinary cancer patientsh,i. Itmay be beneficial to consult a veterinary nutritionist who can formulate a diet specific to the patient.15
Recognition and alleviation of pain in oncology patients is essential for maintaining quality of life. Pain in these patients may be due to the cancer itself, a treatment modality being used (e.g.,radiation or surgery), or a concurrent disease (e.g., osteoarthritis). To adequately control pain, a combination of more than one pain medication (NSAIDs, opioids, and adjuvant drugs such as gabapentin) is routinely required. Practitioners have at their disposal comprehensive sources of information on pain management. Most notably, the recently updated AAHA/AAFP Pain Management Guidelines for Dogs and Cats provide current recommendations for a multimodal approach to preempting and controlling pain.16