Chapter 18. Supportive Care of the Cancer Patient
SECTION A Prevention and Management of Nausea and Vomiting
Mary Lynn Higginbotham
INCIDENCE OF CHEMOTHERAPY-ASSOCIATED NAUSEA AND VOMITING
The management of chemotherapy-associated nausea and vomiting is an important aspect in the treatment of animals with cancer. Quality of life (QOL) is of utmost importance to owners and practitioners alike and therefore pre-emptive treatment of chemotherapy side effects is necessary. A 1983 survey of human oncology patients found that nausea and vomiting are the most feared side effects of chemotherapy, 1 and, in the author’s experience, this is true for pet owners as well. When nausea and vomiting occur, the practitioner is not only faced with the sick patient, but also with poor compliance of the recommended therapy and/or decreased dose and dose intensity, resulting in an inferior long-term outcome for the patient. In addition, chemotherapy-associated nausea and vomiting (CANV) is easier to prevent than it is to treat. Few studies have been performed in veterinary medicine evaluating the incidence or treatment of CANV; therefore, most information on this subject has been derived from the human literature and clinical experience.
CLASSIFICATION OF CHEMOTHERAPY-ASSOCIATED NAUSEA AND VOMITING
CANV can be classified into three categories: acute, delayed, and anticipatory. 2-4 Acute vomiting is described as vomiting within 24 hours of receiving chemotherapy; delayed is vomiting after the first 24 hours of receiving chemotherapy; and anticipatory is a conditioned response to previous vomiting, either acute or delayed, in response to chemotherapy. 2-4 Chemotherapy-associated vomiting is drug and patient dependent. Whereas anticipatory vomiting is rarely encountered, delayed vomiting is most common in veterinary patients.
MECHANISMS OF CHEMOTHERAPY-ASSOCIATED NAUSEA AND VOMITING
Vomiting is mediated through the vomiting center located in the reticular formation of the medulla oblongata. The vomiting center receives stimulatory input from various afferent pathways, including the cerebral cortex, the chemoreceptor trigger zone (CRTZ), the vestibular apparatus, and vagal or sympathetic stimulation from peripheral sensory receptors such as those located within the abdominal viscera, including the GI tract. 5,6 The CRTZ is located in the area postrema of the medulla, where the blood–brain barrier is less effective and is thus able to detect toxins in the blood and CSF. 5,7 The CRTZ stimulates the vomiting center by releasing neurotransmitters. Neurotransmitters involved in emesis include serotonin (5-HT 3 ), substance P, dopamine, histamine, and enkephalins, among others. In addition to stimulation of the CRTZ, chemotherapeutic agents may stimulate the vomiting center via vagal afferents caused by release of serotonin from the enterochromaffin cells within the GI tract wall. 3 Serotonin has been implicated as a primary mediator of acute phase CANV but does not appear to be as important in the delayed phase of CANV, 8 whereas substance P may play more of a role in delayed CANV. 4,8
PHARMACOLOGY OF CHEMOTHERAPY-ASSOCIATED NAUSEA AND VOMITING
Serotonin Receptor Antagonists
Although there are several generations of 5-HT 3 receptor antagonists, those most commonly used in veterinary medicine include dolasetron (Anzemet) and ondansetron (Zofran). These agents bind to both the 5-HT 3 receptors located peripherally on the afferent vagal neurons of the GI tract as well as those located in the CRTZ. Metoclopramide has also been shown to be a weak antagonist of peripheral 5-HT 3 receptors at high doses. 3
Neurokinin-1 Receptor Antagonists
Neurokinin-1 (NK-1) receptor antagonists inhibit the binding of substance P to NK-1 receptors in the vomiting center, perhaps inhibiting both peripherally and centrally mediated vomiting. An NK-1 receptor antagonist, maropitant (Cerenia, Pfizer Animal Health, New York), was approved in 2007 for use in dogs as a general antiemetic. A recent study has shown maropitant to be more effective than metoclopramide when treating vomiting of various causes. 9 Maropitant was also found to be effective at preventing and controlling emesis associated with cisplatin administration when compared with placebo. 10,11
Dopamine Receptor Antagonists
Dopamine receptor antagonists also have some anti-emetic activity by inhibiting stimulation of the emetic center by the CRTZ. Metoclopramide is the most frequently used antidopaminergic agent. Another class of frequently used antidopaminergic agents is the phenothiazines, including prochlorperazine (Compazine) and chlorpromazine (Thorazine). These agents may also have antihistaminic and weak anticholinergic effects that also contribute to their function as anti-emetics. The efficacy of dopamine receptor antagonists in treating CANV is limited at best.
Opiates
Opiate receptors are found in abundance in the CRTZ; although some narcotic agents can induce emesis, others have anti-emetic properties. Butorphanol significantly reduces the emetogenesis associated with cisplatin 12 and streptozocin 13 administration in dogs. One side effect to note with butorphanol is the sedative effect associated with its use.
Histamine Receptor Antagonists
Histamine receptors are also found in abundance within the CRTZ; however, the H 2 receptor antagonists such as cimetidine, ranitidine, and famotidine are not effective as anti-emetic agents. Diphenhydramine and other H 1 receptor antagonists also have not been shown to be helpful for CANV. 3
USE OF ANTI-EMETIC AGENTS IN THE ONCOLOGY PATIENT
For those agents that are highly emetogenic and likely to cause acute CANV (cisplatin and streptozocin) pretreatment anti-emetic agents such as butorphanol or maropitant, are a necessity. Butorphanol has been effective when given subcutaneously 20 minutes before cisplatin administration, 12 as has maropitant when given subcutaneously 1 hour before cisplatin administration. 10 No standard protocols exist for treatment of delayed CANV; however, using agents such as ondansetron or maropitant as necessary for symptomatic care is reasonable. In addition, for patients that have experienced delayed CANV with previous chemotherapy doses, pre-treatment with an antiemetic as well as dispensing an oral formulation (available for ondansetron and maropitant) for at-home use to control CANV is recommended (see Table 18-1 for anti-emetic agents used in veterinary medicine).
| 5-HT 3 , 5-hydroxytryptamine (serotonin); K9, canine; PO, per os; SQ, subcutaneous; IM, intramuscular; IV, intravenous; CRI, continuous rate infusion; Fe, feline; NK-1, neurokinin-1. | |||||
| Drug | Trade Name | Mechanismof Action | Dose | Route | Frequency |
|---|---|---|---|---|---|
| Metoclopramide | Reglan | Dopamine antagonist | K9: 0.1–0.4 mg/kg | PO, SQ, IM | q6–8h |
| Weak peripheral 5-HT 3 antagonist | 1–2 mg/kg/day | IV CRI | |||
| Fe: 0.2–0.4 mg/kg | PO, SQ | q6–8h | |||
| 1–2 mg/kg/day | IV CRI | ||||
| Dolasetron | Anzemet | 5-HT 3 antagonist | K9: 0.5–0.6 mg/kg | PO, SQ, IV | q24h |
| Fe: 0.6 mg/kg | IV | q24h | |||
| Ondansetron | Zofran | 5-HT 3 antagonist | K9: 0.1–1.0 mg/kg | PO, IM | q12–24h |
| 0.11–0.22 mg/kg | IV | ||||
| Fe: 0.1–0.15 mg/kg | IV | q6–12h | |||
| Maropitant | Cerenia | NK-1 receptor antagonist | K9: 1.0. mg/kg | SQ | q24h (max 5 d) or 1 hr before cisplatin administration |
| 2 mg/kg | PO | q24h (max 5 d) | |||
| Prochlorperazine | Compazine | Dopamine antagonist | K9: 0.1–0.5 mg/kg | IM, SQ | q8h |
| Histamine antagonist | Fe: 0.1–0.5 mg/kg | IM, SQ | q8h | ||
| Anticholinergic | |||||
| Chlorpromazine | Thorazine | Dopamine antagonist | K9: 0.1–0.5 mg/kg | IM, SQ | q6–8h |
| Histamine antagonist | Fe: 0.22–0.5 mg/kg | IM, SQ | q6–8h | ||
| Anticholinergic | |||||
| Butorphanol | Torbugesic | Opiate antagonist | K9: 0.4 mg/kg | IM, SQ | 20 min before cisplatin or immediately after streptozotocin administration |
SPECIES VARIATIONS
Species variations important to the management of veterinary patients should be noted. Rather than vomiting, cats tend to have more nausea and anorexia associated with treatment. Although metoclopramide may be used in felines, it can cause excitement. More often, steroids or cyproheptadine (an antiserotonergic agent) may be used as appetite stimulants and a transdermal formulation of cyproheptadine is available to avoid the added stress of pilling cats.
SUMMARY
Because of the multifactorial nature of CANV and inter-patient and species variations, it is important to consider anti-emetic agents associated with each individual situation. Pre-emptive attempts at controlling nausea and vomiting will help decrease both acute and delayed CANV and help improve the QOL of our patients while undergoing treatment. It will also prevent undesirable delays and dose reductions, ultimately decreasing the efficacy of our chemotherapy protocols.
Selected References ∗
V.A. Puente-Redondo, E.M. Siedek, H.A. Benchaoui, et al. , The antiemetic efficacy of maropitant (Cerenia™) in the treatment of ongoing emesis caused by a wide range of underlying clinical aetiologies in canine patients in Europe , J Small Anim Pract 48 ( 2 ) ( 2007 ) 93 ;
Prospective study evaluating the efficacy of the NK-1 receptor antagonist, maropitant, for vomiting induced by multiple causes .
D.M. Vail, H.S. Rodabaugh, G.A. Conder, et al. , Efficacy of injectable maropitant (Cerenia) in a randomized clinical trial for prevention and treatment of cisplatin-induced emesis in dogs presented as veterinary patients , Vet Comp Oncol 5 ( 1 ) ( 2007 ) 38 ;
Prospective study evaluating the efficacy of maropitant as an anti-emetic in cisplatin-treated dogs .
R.J. Washabau, M.S. Elie, Antiemetic therapy , In: (Editor: J.D. Bonagura) Kirk’s current veterinary therapy XII: small animal practice ( 1995 ) WB Saunders , Philadelphia , p. 679 ;
In-depth review of the physiology of vomiting and pharmacology of anti-emetic agents available in 1995 .
SECTION B Nutritional Management of the Cancer Patient
S. Dru Forrester, Philip Roudebush and Deborah J. Davenport
KEY POINTS
• Nutritional management is an important component of cancer care that may affect quality of life and survival time.
• One therapeutic food containing increased amounts of omega-3 fatty acids and the amino acid arginine has been shown to improve survival and quality of life in dogs with cancer.
• To lessen the likelihood of side effects (e.g., diarrhea), it is critical to gradually (over 10–14 days) transition to therapeutic foods formulated for cancer patients.
• If feeding a therapeutic food is not possible, it is important to facilitate caloric intake and maintain body condition by feeding a complete and balanced food that the patient will eat.
• Nutritional recommendations for overweight or obese cancer patients may need to be adjusted, especially if there are concomitant conditions (e.g., increased risk for pancreatitis, arthritis).
• Many supplements have been suggested for cancer patients; however, most have not been critically evaluated in dogs or cats.
Nutritional management can improve quality and quantity of life for cancer patients. Many owners understand the importance of nutrition in cancer patients and are willing to implement nutritional recommendations that can potentially increase the quality of their pet’s life. This chapter reviews metabolic consequences of cancer, evidence supporting nutritional intervention in dogs and cats with cancer, and guidelines for implementing nutritional management.
NUTRITIONAL CONSEQUENCES OF CANCER AND CANCER TREATMENT
Weight loss and decreased body condition may occur in cancer patients as a result of tumor location (e.g., oral masses), cancer cachexia, or complications of cancer treatment (e.g., decreased appetite caused by chemotherapy). Cancer cachexia is a paraneoplastic syndrome characterized by progressive weight loss and decreased body condition, despite adequate nutritional intake. It is not known how many dogs and cats with cancer suffer from cachexia. In a study of dogs presented to a veterinary oncology service, only 4% exhibited cachexia, defined as thin body condition, whereas 29% were markedly overweight. 1 However, 15% had clinically relevant muscle wasting, and 68% had lost weight compared with their body weight before cancer was diagnosed. In the same study, dogs with hematopoietic neoplasia (e.g., lymphoma) were significantly more likely to lose more weight compared with dogs with solid tumors. Human patients with cancer cachexia respond less favorably to treatment and have decreased survival time compared with patients that have not lost weight. 2-6 Cachexia also has negative effects on quality of life in human cancer patients. 2,3 It seems reasonable that similar consequences occur in veterinary cancer patients; however, this has not been critically evaluated.
METABOLIC ALTERATIONS IN CANCER PATIENTS
Dogs with lymphoma and other malignant diseases have significant alterations in carbohydrate metabolism; these alterations occur because tumors preferentially metabolize glucose (carbohydrates) for energy, forming lactate as an end product. 7-12 Dogs with cancer must then expend energy to convert lactate back to glucose, resulting in a net energy gain by the tumor and net energy loss by the patient. Following intravenous administration of glucose, dogs with cancer have increased blood lactate and insulin concentrations, which persists after successful treatment with chemotherapy or surgery. 10,13 In addition, administration of lactate-containing fluids increases blood lactate concentrations in dogs with lymphoma; these findings are the basis for recommending avoidance of glucose- or lactate-containing fluids in dogs with cancer. 11
In addition to altered carbohydrate metabolism, cancer patients have altered protein and fat metabolism. In one study, cancer-bearing dogs had significantly lower plasma concentrations of several amino acids (e.g., arginine); these alterations in plasma amino acid profiles did not normalize after tumors were removed surgically. 14 Altered lipid profiles have also been reported in dogs with lymphoma. 9 Decreased fat synthesis or increased lipolysis can deplete fat stores and contribute to cachexia; several cytokines (e.g., tumor necrosis factor alpha) produced in cancer patients appear responsible for altered lipid metabolism and may contribute to cachexia.
THE IDEAL NUTRITIONAL PROFILE FOR PATIENTS WITH CANCER
Nutritional management is an important component of multi-modality therapy of dogs and cats with cancer and should be given equal consideration when planning treatment (chemotherapy, radiotherapy, surgery, and pain management). Providing appropriate nutrition may improve QOL, enhance effectiveness of cancer treatment, and increase survival time. Pending further studies in cats, therapeutic principles for feline patients with cancer should follow those for people and dogs with cancer. Key nutritional factors in dogs and cats with cancer include soluble carbohydrate, fiber, protein, arginine, fat, and omega-3 fatty acids ( Table 18-2 ). It is also critical to supply the pet’s energy needs (i.e., calories) to maintain ideal body condition.
| NA, Information not available from manufacturer | ||||||
| ∗ Nutrients expressed on a percent dry matter basis unless otherwise indicated. Values obtained from manufacturers’ published information. | ||||||
| † Data from Debraekeleer J: Nutrient profiles of commercial dog and cat foods (Appendix L). In Hand MS, Thatcher CD, Remillard RL. et al (eds): Small animal clinical nutrition , ed 4, Topeka, 2000, Mark Morris Institute, pp 1073-1083. | ||||||
| Protein | Soluble Carbohydrate | Fat | Omega-3 Fatty Acids | Arginine | Crude Fiber | |
|---|---|---|---|---|---|---|
| Recommended levels for dogs with cancer | 30–45 | <25 | 25–40 | >5 | >2.5 | >2.5 |
| Recommended levels for cats with cancer | 40–50 | <25 | 25–40 | 2-3 | >2.5 | >2.5 |
| Products | ||||||
| Hill’s Prescription Diet n/d Canine, moist | 38 | 20 | 33.2 | 7.3 | 2.95 | 2.7 |
| Hill’s Prescription Diet a/d Canine/Feline, moist | 44.2 | 15.4 | 30.4 | 2.6 | 2.4 | 1.3 |
| Hill’s Prescription Diet p/d Feline, moist (Canada) | 49 | 16.2 | 24 | 1 | 2.3 | 2.8 |
| Hill’s Prescription Diet p/d Feline, dry (Canada) | 39 | 24 | 29 | 1.1 | 2.2 | 1.3 |
| Hill’s Science Diet Puppy Healthy Development Savory Chicken Entrée | 28.2 | 39.2 | 23.6 | 0.4 | 1.8 | 1.3 |
| Hill’s Science Diet Kitten Healthy Development Liver & Chicken Entrée | 49 | 16 | 24 | 1 | 2.3 | 2.8 |
| Hill’s Prescription Diet m/d Feline, dry | 52 | 14.7 | 22 | 0.23 | 2.64 | 5.9 |
| Hill’s Prescription Diet m/d Feline, moist | 53 | 15.7 | 19.4 | 0.3 | 3.2 | 6.0 |
| Iams Eukanuba Maximum Calorie/Canine & Feline, moist | 42 | 12 | 37 | 0.22(minimum) | NA | 0.5 |
| Purina CV Feline Formula, moist | 42.5 | 23 | 27 | NA | NA | 1 |
| Purina DM Feline Formula, dry | 58 | 15 | 18 | 0.39 | 3.57 | 1.3 |
| Purina DM Feline Formula, moist | 57 | 8.1 | 24 | 0.88 | NA | 3.7 |
| Royal Canin Veterinary Diet Canine and Feline Recovery RS | 53.4 | 2.3 | 33.4 | NA | 5.9 g/1000 kcal | 3.4 |
| Dry grocery brand dog foods (average) † | 25.3 | 52.2 | 12.3 | <1 | <2 | 3.1 |
| Dry specialty brand dog foods (average) † | 28.1 | 45.1 | 16.3 | <1 | <2 | 3.3 |
| Moist grocery brand dog foods (average) † | 41.2 | 19.9 | 27.1 | <1 | <2 | 1.8 |
| Dry grocery brand cat foods (average) † | 34.8 | 43.9 | 12.3 | <1 | <2 | 2.2 |
| Dry specialty brand cat foods (average) † | 35.3 | 37.4 | 18.5 | <1 | <2 | 2.4 |
| Moist grocery brand cat foods (average) † | 51.2 | 9.7 | 26.6 | <1 | <2 | 1.5 |
Soluble Carbohydrate and Fiber
Most adult, non-producing dogs and cats do not require soluble carbohydrates; however, pet food manufacturers include ingredients with soluble carbohydrates because they are good energy sources and their unique properties aid in manufacturing processes. Soluble carbohydrates may be poorly used by pets with cancer and can contribute to increased lactate production. For this reason, it is recommended that soluble carbohydrates comprise <25% of food on a dry matter basis ( Table 18-2 ). Soluble (fermentable) and insoluble (poorly fermentable) fiber sources may help maintain intestinal health, especially in pets undergoing cancer treatment. Increased dietary fiber may help manage abnormal stool quality or diarrhea, which may occur when changing from high-carbohydrate, dry foods to high-fat commercial or homemade foods.
Protein and Arginine
Dietary protein should be highly digestible and exceed maintenance levels for adult dogs and cats because patients with cancer have altered protein metabolism and may suffer loss of lean muscle mass ( Table 18-2 ). Arginine is an essential amino acid that may have specific therapeutic value in pets with cancer. Adding arginine to parenteral solutions decreased tumor growth and metastatic rates in rodent cancer models. 15,16 Increased dietary arginine in conjunction with increased dietary omega-3 fatty acid intake improved clinical signs, QOL, and survival time in dogs treated for cancer. 17,18 The minimal effective level of dietary arginine for pets with cancer is unknown; however, the positive correlation between plasma arginine concentrations and survival in dogs with lymphoma suggests it should be >2.5% arginine on a dry matter basis.
Fat and Omega-3 Fatty Acids
Some tumor cells have difficulty using lipids as a fuel source, whereas host tissues can use lipids for energy. This finding led to the hypothesis that foods relatively high in fat may benefit pets with cancer compared with foods relatively high in carbohydrates. In North America, pets receive most of their nutrient intake from commercial dry pet foods; these foods are usually high in soluble carbohydrate (25%–60%) and relatively low in fat (7%–25%). These characteristics make most of these foods inappropriate for nutritional management of dogs with cancer; this may also be true for cats, although it has not been evaluated (see Table 18-2 ).
Omega-3 fatty acids, especially those found in certain types of fish and fish oil (eicosapentaenoic acid [EPA], docosahexaenoic acid [DHA]), are probably the most important to consider for pets with cancer. Fish oil and EPA/DHA supplementation have many beneficial effects, including inhibition of lipolysis and muscle protein degradation associated with cachexia. Several human epidemiologic studies have suggested that consumption of fish or higher levels of omega-3 fatty acids protect against certain types of cancer. The recommendation for feeding high levels of omega-3 fatty acids such as EPA and DHA to pets with cancer is based on in vitro cell culture studies, extensive studies in rodent cancer models, clinical trials in human patients with severe forms of cancer, and clinical trials in dogs treated for lymphoma and nasal tumors. 19
Antioxidants
Use of antioxidants in cancer patients is somewhat controversial. Some believe that supplementation with high-dose dietary antioxidants such as vitamin E may improve effectiveness of cancer therapy by enhancing immune function, increasing tumor response to radiation or chemotherapy, decreasing toxicity to normal cells, and helping reverse metabolic changes contributing to cachexia. Others believe that dietary antioxidants may protect cancer cells against damage by chemotherapy or radiation therapy. At present, megadose vitamin therapy does not appear indicated if pets are fed a complete and balanced commercial food. Instead, levels of vitamin E and other antioxidant nutrients should be appropriate for the level of polyunsaturated fatty acids, trace minerals, and oxidants in the food.
EVIDENCE SUPPORTING NUTRITIONAL MANAGEMENT OF CANCER PATIENTS
Several well-controlled clinical trials have evaluated a high-fat, low-carbohydrate, arginine- and fish oil–supplemented therapeutic food (Prescription Diet n/d Canine, Hill’s Pet Nutrition, Inc.) in dogs undergoing single-agent chemotherapy for lymphoma with doxorubicin or radiation therapy for nasal tumors. 17,18,20 Dogs fed the therapeutic food had higher serum concentrations of omega-3 fatty acids and arginine compared with dogs fed the unsupplemented control food. Higher concentrations of EPA and DHA were associated with lower plasma lactic acid responses and longer disease-free interval and median survival time in dogs with Stage III lymphoma. 18 In one study, improved QOL was noted in dogs with lymphoma fed the fish oil and arginine supplemented food. 20 Additional beneficial effects (i.e., lower tissue concentrations of inflammatory mediators, improved performance scores, and less histologic damage to normal tissues from radiation therapy) were observed in dogs undergoing radiation therapy for nasal tumors when fed the fish oil and arginine–supplemented food. 17 It is expected that similar clinical responses would occur in patients with a wide range of cancer types; however, this has not been reported.
FORMULATING A NUTRITIONAL PLAN FOR CANCER PATIENTS
The goals of nutritional management of cancer patients are to provide adequate nutrients to facilitate recovery, minimize metabolic consequences of cancer, and maintain lean body mass. Before establishing and implementing a nutritional plan for cancer patients, it is helpful to remember these goals, which help guide patient assessment and monitoring, nutritional recommendations, and education of pet owners.
Patient Assessment
A thorough dietary history should be obtained prior to initial management of cancer patients. This should include detailed information about current foods (brands, quantity, and frequency) and any over-the-counter supplements. Physical examination should include weighing the patient and determining body condition. Body condition can be assessed by assigning a score ranging from 1 to 5 (1 = very thin, 3 = ideal body condition, 5 = grossly obese). 21 This is a more objective method for determining fat stores and body composition. A body condition score should be determined and recorded in the patient’s medical record along with body weight as a routine part of the physical examination at each visit. This allows for detecting changes in body condition over time, which is important in cancer patients.
Selecting a Food
Selecting the appropriate food for management of cancer patients should include consideration of owner/pet preferences, body condition, and presence of concurrent diseases. Foods prepared by a reputable manufacturer and tested in feeding trials are preferred over homemade foods because they are more likely to provide complete and balanced nutrition, are more readily available, and are convenient to use. When owners are interested in preparing homemade foods, veterinarians should consult a clinical nutritionist or additional resources to assist with creating a nutritionally balanced food. 22 Based on current evidence, the authors believe that bones and raw food (BARF) diets should not be fed because cancer patients are immunocompromised and are at risk for septicemia as a result of bacterial contamination. 23,24 Body condition and presence of concurrent disorders must also be considered when selecting a food. Foods formulated for cancer patients are relatively high in fat, which is appropriate for dogs and cats that are underweight or in good body condition. However, they may not be ideal for overweight or obese patients, particularly if there are concomitant conditions such as pancreatitis, hyperlipidemia, osteoarthritis, or anticipated need for amputation of a limb (e.g., osteosarcoma). When managing patients with multiple problems, it may be helpful to consult with a clinical nutritionist for advice.
Several commercially available foods provide key nutrients in appropriate levels for cancer patients ( Table 18-2 ). One food (Prescription Diet n/d Canine) has been shown to improve lifespan and QOL in selected canine patients with cancer. 18,25 Similar foods are recommended in cats with cancer, although no studies have been done to evaluate their effects. When changing to a food with increased fat, it is critical to gradually transition (over a period of 10–14 days) to the new food in order to avoid complications. Sudden introduction of a food containing relatively higher amounts of fat may cause unacceptable side effects (e.g., refusal to eat the new food, loose stools or severe diarrhea), causing pet owners to abandon a potentially beneficial treatment. It may also be helpful to divide the daily food amount and give three to six small meals per day during the initial feeding of the new food. In patients that will not eat a recommended therapeutic food, it is reasonable to try a different food. When owners are not willing or able to purchase a therapeutic food formulated for cancer patients, it is important to maintain caloric intake and body condition by offering a complete and balanced food that the patient will eat.
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