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Nutrition During Cancer

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Nutrition in Cancer Care

This content is a selection of "Nutrition in Cancer Care (PDQ®)-Health Professional Version" developed by the National Cancer Institute at the National Institutes of Health.
Full content is available at: http://www.cancer.gov/cancertopics/pdq/supportivecare/nutrition/HealthProfessional

Overview

Nutrition plays major (but not always fully understood) roles in many aspects of cancer development and treatment.1 Malnutrition is a common problem in cancer patients that has been recognized as an important component of adverse outcomes, including increased morbidity and mortality and decreased quality of life.

Weight loss has been identified as an indicator of poor prognosis in cancer patients.2 It has been shown that at the time of diagnosis, 80% of patients with upper gastrointestinal cancer and 60% of patients with lung cancer have already experienced a significant weight loss,3 generally defined as at least a 10% loss of body weight in 6 months' time.4

Good nutrition practices can help cancer patients maintain weight and the body's nutrition stores, offering relief from nutrition impact symptoms and improving quality of life. 5 Poor nutrition practices, which can lead to undernutrition, can contribute to the incidence and severity of treatment side effects and increase the risk of infection, thereby reducing chances for survival.6

Nutrition impact symptoms are those symptoms that impede oral intake. They include, but are not limited to, anorexia, nausea, vomiting, diarrhea, constipation, stomatitis, mucositis, dysphagia, alterations in taste and smell, pain, depression, and anxiety.7 Early recognition and detection of risk for malnutrition through nutrition screening followed by comprehensive assessments is increasingly recognized as imperative in the development of standards of quality of care in oncology practices.2 Undesirable weight gain may be an effect of chemotherapy treatment for early-stage cancers, possibly resulting from decreases in resting metabolism.8 Consequently, the eating practices of individuals diagnosed with cancer should be assessed throughout the continuum of care to reflect the changing goals of nutritional therapy.

Nutritional status is often jeopardized by the natural progression of neoplastic disease. Alterations in nutritional status begin at diagnosis, when psychosocial issues may also adversely affect dietary intake, and proceed through treatment and recovery. Protein-calorie malnutrition (PCM) is the most common secondary diagnosis in individuals diagnosed with cancer, stemming from the inadequate intake of carbohydrate, protein, and fat to meet metabolic requirements and/or the reduced absorption of macronutrients. PCM in cancer results from multiple factors most often associated with anorexia, cachexia, and the early satiety sensation frequently experienced by individuals with cancer. These factors range from altered tastes to a physical inability to ingest or digest food, leading to reduced nutrient intake.

Cancer-induced abnormalities in the metabolism of the major nutrients also increase the incidence of PCM. Such abnormalities may include glucose intolerance and insulin resistance, increased lipolysis, and increased whole-body protein turnover. If left untreated, PCM can lead to progressive wasting, weakness, and debilitation as protein synthesis is reduced and lean body mass is lost, possibly leading to death.9

Anorexia, the loss of appetite or desire to eat, is typically present in 15% to 25% of all cancer patients at diagnosis and may also occur as a side effect of treatments. Anorexia is an almost universal side effect in individuals with widely metastatic disease 10,11 because of physiologic alterations in metabolism during carcinogenesis. Anorexia can be exacerbated by chemotherapy and radiation therapy side effects such as taste and smell changes, nausea, and vomiting. Surgical procedures, including esophagectomy and gastrectomy, may produce early satiety, a premature feeling of fullness.4 Depression, loss of personal interests or hope, and anxious thoughts may be enough to bring about anorexia and result in PCM.3 Evidence-based recommendations have been published describing various approaches to the problems of cancer-related fatigue, anorexia, depression, and dyspnea.12 Other systemic or local effects of cancer or its treatment that may affect nutritional status include hypermetabolism, sepsis, malabsorption, and obstructions.9

Anorexia can hasten the course of cachexia,3 a progressive wasting syndrome evidenced by weakness and a marked and progressive loss of body weight, fat, and muscle. Cachexia is estimated to be the immediate cause of death in 20% to 40% of cancer patients; it can develop in individuals who appear to be eating adequate calories and protein but have primary cachexia whereby tumor-related factors prevent maintenance of fat and muscle. Particularly at risk are patients with diseases of the gastrointestinal tract.

The etiology of cancer cachexia is not entirely understood. Cachexia can manifest in individuals with metastatic cancer as well as in individuals with localized disease. Several theories suggest that cachexia is caused by a complex mix of variables, including tumor-produced factors and metabolic abnormalities.11 The basal metabolic rate in cachectic individuals is not adaptive, that is, it may be increased, decreased, or normal.13 Some individuals do respond to nutrition therapy, but most will not see a complete reversal of the syndrome, even with aggressive therapy.6 Thus, the most prudent and advantageous approach to cachexia is the prevention of its initiation through nutrition monitoring and nutrition intervention.14

Nutrition Screening and Assessment

Nutrition in cancer care embodies prevention of disease, treatment, cure, or supportive palliation. Caution should be exercised when considering alternative or unproven nutritional therapies during all phases of cancer treatment and supportive palliation, as these diets may prove harmful. Patient nutritional status plays an integral role in determining not only risk of developing cancer but also risk of therapy-related toxicity and medical outcomes. Whether the goal of cancer treatment is cure or palliation, early detection of nutritional problems and prompt intervention are essential.

The original principles of nutrition care for people diagnosed with cancer were developed in 1979 15 and are still very relevant today. Proactive nutritional care can prevent or reduce the complications typically associated with the treatment of cancer.15

Many nutritional problems stem from local effects of the tumor. Tumors in the gastrointestinal tract, for example, can cause obstruction, nausea, vomiting, impaired digestion, and/or malabsorption. In addition to the effects of the tumor, marked alterations in normal metabolism of carbohydrates, protein, and/or fats can occur.10

The nutritional prognostic indicators most recognized as being predictive of poor outcome include weight loss, wasting, and malnutrition. In addition, significant weight loss at the time of diagnosis has been associated with decreased survival and reduced response to surgery, radiation therapy, and/or chemotherapy.16

Malnutrition and accompanying weight loss can be part of an individual’s presentation or can be caused or aggravated by treatments for the disease. Identification of nutrition problems and treatment of nutrition-related symptoms have been shown to stabilize or reverse weight loss in 50% to 88% of oncology patients.17

Screening and nutrition assessment should be interdisciplinary; the healthcare team (e.g., physicians, nurses, registered dietitians, social workers, psychologists) should all be involved in nutritional management throughout the continuum of cancer care.18 A number of screening and assessment tools are currently available for use in nutritional assessment. Examples of these tools include the Prognostic Nutrition Index,19,20 delayed hypersensitivity skin testing, institution-specific guidelines, and anthropometrics. Each of these tools can help identify persons at nutritional risk; unfortunately, the values obtained using such tools can be altered by the hydration status and the immune compromise frequently found in individuals diagnosed with cancer. In addition, each of these objective measures can carry a cost in terms of laboratory or practitioner time. One author has provided a useful overview of assessment procedures for advanced cancer patients.21

Another example of a screening and assessment procedure is the Patient-Generated Subjective Global Assessment (PG-SGA). Based on earlier work on a protocol called Subjective Global Assessment (SGA),22 the PG-SGA is an easy-to-use and inexpensive approach in identifying individuals at nutritional risk and in triaging for subsequent medical nutritional therapy in a variety of clinical settings2,23 The individual and/or caretaker complete sections on weight history, food intake, symptoms, and function. A member of the healthcare team evaluates weight loss, disease, and metabolic stress and performs a nutrition-related physical examination. A score is generated from the information collected. The need for nutrition intervention is determined according to the score.

Bioelectrical impedance analysis (BIA) is also used to assess nutritional status, as determined by body composition.24 The BIA measures electrical resistance on the basis of lean body mass and body fat composition. Single BIA measures show body cell mass, extracellular tissue, and fat as a percent of ideal, whereas sequential measurements can be used to show body composition changes over time. Because of cost and accessibility, BIA is currently in limited use and often unavailable in most ambulatory settings.

Taste and smell defects are common in cancer patients and may affect nutritional status. The relative importance of chemosensory changes to the etiology of malnutrition was assessed in 66 patients with advanced cancer. Some degree of chemosensory abnormality was reported by 86% of patients; approximately one-half of patients reported interference with enjoying favorite foods. Poor appetite, nausea, early satiety, and chemosensory abnormalities presented concurrently. These findings were significantly related to decreased energy intake. Further research is required to design nutritional interventions for these chemosensory problems.25

Because nutritional status can quickly become compromised from illness and decreased dietary intake, and because nutritional well-being plays an important role in treatment and recovery from cancer, early screening and intervention as well as close monitoring and evaluation throughout all phases of cancer treatment and recovery are imperative in the pursuit of health for the individual with cancer.

Goals of Nutrition Therapy

Optimal nutritional status is an important goal in the management of individuals diagnosed with cancer. Although nutrition therapy recommendations may vary throughout the continuum of care, maintenance of adequate intake is important. Therefore, a waiver from most dietary restrictions observed during religious holidays is granted for those undergoing active treatment. Individuals with cancer are encouraged to speak to their religious leaders regarding this matter before a holiday.

Whether patients are undergoing active therapy, recovering from cancer therapy, or in remission and striving to avoid cancer recurrence, the benefit of optimal caloric and nutrient intake is well documented.26-28

The goals of nutrition therapy are to accomplish the following:

  • Prevent or reverse nutrient deficiencies
  • Preserve lean body mass
  • Help patients better tolerate treatments
  • Minimize nutrition-related side effects and complications
  • Maintain strength and energy
  • Protect immune function, decreasing the risk of infection
  • Aid in recovery and healing
  • Maximize quality of life.

Patients with advanced cancer can receive nutritional support even when nutrition therapy can do little for weight gain.[bib14,29bib] Such support may help accomplish the following:

  • Lessen side effects
  • Reduce risk of infection (if given enterally)
  • Reduce asthenia
  • Improve well-being.

In individuals with advanced cancer, the goal of nutrition therapy should not be weight gain or reversal of malnutrition, but rather comfort and symptom relief.5

Nutrition continues to play an integral role for individuals whose cancer has been cured or who are in remission.30 A healthy diet helps prevent or control comorbidities such as heart disease, diabetes, and hypertension. Following a healthful nutrition program might help prevent another malignancy from developing.

References

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