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  and are still very relevant today. Proactive nutritional care can prevent or reduce the complications typically associated with the treatment of cancer.
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.
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.
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.
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.
A number of screening and assessment tools are currently available for use in nutritional assessment. Examples of these tools include the Prognostic Nutrition Index,[6,7] 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.
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), 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 settings.[10,11] 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.