Page 323 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 16 Supportive Care for the Cancer Patient 301

alterations in olfactory and taste senses. 258 Because dogs and cats Epidemiology, Prevention, and Risk Factors
rely heavily on olfactory cues, the loss of olfactory bulb stimulus In humans the two major nutritional factors associated with the
Additionally, the loss
258,259
diminishes the palatability of foods.
VetBooks.ir or alteration of taste (ageusia or dysgeusia) can further complicate relative risk of developing cancer are body weight (obesity) and
fruit and vegetable consumption.
271–274
anorexia and may last for several months before neuronal regen-
Although these param-
eration can take place at the olfactory bulb and tongue. 258,259 eters may be interrelated, both appear to play a role in carcinogen-
Cachexia, on the other hand, although identified in many esis. Convincing data indicate that the westernized diet and lack
human cancer patients, does not appear to be common in dogs of fruit and vegetable matter are linked to an increased relative
with nonhematopoietic malignancies. 251,255,260,261 Evidence in risk of nearly all types of neoplasia, including prostate, colon, and
humans and mouse models suggests that the most prominent breast cancers, lymphomas, and leukemias. 275–277 It is not yet clear
influence inciting the cachectic phenomenon may be excessive whether this increased relative risk is due to a decreased dietary
cytokine stimulation, which leads to insulin resistance, extensive intake of fiber, carotenoids, and flavonoids or to an increased
lipolysis, and proteolysis of tissue stores. 262,263 The three primary intake of saturated fat and protein. In people consuming higher
cytokines thought to be involved in promoting enhanced proteol- amounts of fruits and vegetables, it is apparent that combined fac-
ysis are tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL- tors may be involved, in addition to confounding lifestyle differ-
1β), and IL-6. 262,263 TNF-α and IL-1β have both been directly ences, that may be important.
associated with anorexia and upregulation of the mitochondrial Few studies in veterinary medicine have examined the effects
uncoupling protein, whereas IL-6 and TNF-α have been observed of dietary substrate (protein, fat, and carbohydrate) and plant-
to increase myofibrillar degradation machinery—all of which may based dietary intake and cancer incidence. Two epidemiologic
play a role in the anorexia/cachexia syndrome associated with neo- studies used validated food frequency questionnaires to exam-
plasia. 264,265 IL-6 and C-reactive protein, both markers of inflam- ine the calories coming from fat, protein, and carbohydrate
mation, are increased in canine lymphoma patients. 257,266,267 for 1 year before diagnosis of mammary carcinoma and after
Yet it does not appear that cachexia is a common occurrence in diagnosis and compared this with survival data. 278,279 This data
dogs diagnosed with neoplasia, because dogs examined 6 months was contradictory to human findings because dogs with an
before diagnosis of cancer showed no difference in body weight increased protein intake had increased STs after diagnosis, and
or body condition than when presenting with various neopla- fat and carbohydrate intake did not play a role in progression
sias. 260 This may be partially explained by differences in common of the disease. 278,279 In another study the risk of neoplasia was
tumor types between species. Cachexia in humans is often associ- increased in dogs fed nontraditional, poorly balanced diets (i.e.,
ated with epithelial cancers, such as pancreatic, colon, mammary, table foods as primary consumption). 280 Further examination
and prostate cancer. Additionally, human patients undergo dra- showed no association between blood selenium concentration
matically different and more aggressive treatment protocols over and mammary carcinomas compared with healthy, age-matched
lengthy periods, which we typically do not encounter in veterinary and hospitalized control dogs; however, tissue retinol status was
medicine because of owners’ financial constraints and quality of decreased in dogs with mammary carcinoma. 280 Whether the
life decisions. lower serum retinol resulted from the dogs being fed a commer-
Cats may show a more typical cachectic response involving cial diet with inadequate retinol or was a manifestation of the
excessive lean body mass wasting. Approximately 56% of cats with disease was not determined. Because feeding an incomplete diet
lymphoma and other solid tumors have body condition scores less was associated with an increased risk, feeding a complete and
than 5 out of 9. 268 More intriguing is that the ST for cats with balanced commercial diet is highly recommended. These results
lymphoma with a body condition score of 5 or greater was 16.9 are not surprising considering that food stuffs and methods of
months, compared with 3.3 months for cats with lower scores. 268 feeding are dramatically different between dogs and people. In
This warrants monitoring of caloric intake and aggressive imple- many cases a high-protein food may be evaluated as higher qual-
mentation of nutritional interventions in feline oncology patients. ity because protein is an expensive ingredient; therefore many
These sensitivities should be taken into consideration during confounding variables—such as ingredient inclusion, ingredi-
radiation therapy, for which cats often stay overnight and are ent quality, digestibility, and owner socioeconomic-associated
fasted for multiple days in a row. Providing ample time to consume health provisions—should be considered in studies of this
calorie-dense foods should be considered for the hospitalized cat nature, and such studies cannot be directly compared with
to ensure that food is offered often enough for the cat to maintain human studies.
a normal caloric intake. Anecdotally, 19 of 20 cats undergoing RT A study that examined nutritional risk factors in Scottish terri-
at the author’s (JJW) facility for a month lost weight during treat- ers, which have a genetic predisposition to developing transitional
ment, suggesting that feeding patterns and weight loss should be cell carcinoma (TCC), found that the addition of vegetables to
monitored and ameliorated when possible. the diet resulted in a lower incidence of the disease 281 ; however,
Metronomic feeding surrounding chemotherapy protocols there were confounding lifestyle factors that cannot be accounted
may be beneficial to tumor growth and progression. The exact for in this epidemiologic investigation, including better health
nature of how this would be implemented in dogs and cats is in its care, variation in nutrition supplied as commercial food, and
infancy; however, the concept of starving the tumor during che- other associated environmental exposures. Nevertheless, the find-
motherapy may be beneficial for chemotherapeutic efficacy. 269,270 ings of this study are provocative and suggest that further study is
The typical protocols involve either not feeding the patient or warranted.
limiting feeding in the 24 to 72 hours before chemotherapy to Recent investigations of specific nutrients and cancer treat-
help sensitize the tumor cells to a more stressful environment and ment primarily have focused on oxidative damage in tumors
dampen the inflammation associated with the tumor. Many clini- and antioxidants (addressed in a later section of the chapter).
cal trials are underway in humans to achieve a better understand- Specific vitamins and their relationship to cancer development
ing of this phenomenon. have received significant attention, including retinol, ascorbic