Specialized Nutrition Support

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In 2002, the American Society for Parenteral and Enteral Nutrition (ASPEN) published guidelines for the use of specialized nutrition support (SNS) in oncology patients. The guidelines provide evidence-based direction regarding the use of enteral nutrition (EN) and parenteral nutrition (PN) support.

Enteral nutrition (EN) has been associated with improvements in nitrogen balance and sometimes associated with weight gain in cancer patients [46]. PN has also been associated with improvements in nitrogen balance, and PN appears to more consistently cause weight gain [46]. However, this weight gain is primarily body fat [62] and produces little benefit above improving patient comfort and sense of well-being [46, 63]. Neither EN nor PN in cancer patients has beneficial effects on serum proteins, such as albumin when administered for 7-49 days. SNS appears to have less of a beneficial impact on cancer patients than non-cancer patients, likely because of the overriding importance of the underlying metabolic abnormalities induced by CCS [64].

Enthusiasm for the use of SNS in cancer patients has historically been tempered by concern that provision of nutrients may stimulate tumor growth and metastasis. Investigators have found that PN provision in excess of energy requirements more than doubles the rate of tumor growth in murine models [65-67]. Limited data are available in humans. An increase in tumor cell proliferation and protein synthesis has been observed in head and neck and colorectal cancer patients receiving PN, but it is unlikely that this is of clinical significance [68-70].

The American Gastroenterological Association (2001) and ASPEN (2002) hold similar positions on the use of PN in oncology patients [64, 71]. The use of SNS in cancer patients should generally be reserved for those circumstances where a patient is moderately or severely malnourished as a result of their cancer or cancer therapy or is likely to be unable to meet their nutritional requirements orally for more than 7-10 days, AND in whom future active therapy is planned to treat the underlying malignancy [64]. Table 7.5 presents the general contraindications to SNS. PN should not routinely be given to patients undergoing cancer chemotherapy or radiation therapy. ASPEN guidelines further state that PN is appropriate only in malnourished patients who are anticipated to be unable to ingest and/or absorb adequate nutrients for a prolonged period of time, defined as greater than 7 to 10 days [64]. PN should be avoided in most cases if a patient's life expectancy is less than 40-60 days [64]. If intravenous therapy is felt

Table 7.5

Contraindications to Specialized Nutrition Support in Cancer Patients [64]

Enteral nutrition

Malabsorption GI obstruction GI bleeding Severe diarrhea Intractable vomiting Hemodynamic instability Prognosis and/or social circumstances not consistent with aggressive specialized nutrition support

Parenteral nutrition

Functional gastrointestinal tract Need for nutrition support <5 days Prognosis not consistent with aggressive nutrition support Inadequate vascular access Patient/caregiver request Hemodynamic instability Profound metabolic and/or electrolyte disturbances

From: Huhmann MB, Cunningham RS. Importance of nutritional screening in treatment of cancer-related weight loss. Lancet Oncology. 2005;6: 334-43.

appropriate in an individual with a life expectancy of less than 40 days, hydration therapy with intravenous fluids only is recommended [64].

4.3. Perioperative Nutrition Support

In the 1980s and 1990s, numerous studies examined the relative benefits of enteral nutrition (EN) versus parenteral nutrition (PN) on outcome in cancer patients undergoing elective surgical resections with curative intent.

Early studies indicated reduced morbidity and mortality with perioperative PN supplementation in cancer patients, especially those with gastrointestinal malignancies [72]. However, these studies have been criticized because of the inclusion of heterogeneous populations, variable and likely suboptimal macronutrient provision, and inadequate sample sizes [5]. More recent studies of perioperative PN, primarily in GI cancer patients, indicate increased incidence of infection in patients receiving parenteral nutrition, with no improvement in survival [73-75]. The limited data in significantly malnourished GI cancer patients also indicate no benefit of perioperative PN over EN, but does indicate a benefit over standard isotonic fluids [73-75]. Risks associated with postoperative PN include increased infection rate, increased complication rate and increased cost [74, 76-78].

The many trials attempting to assess the efficacy of enteral nutrition in perioperative care are difficult to compare because of differing definitions of malnutrition and study designs. Enteral administration of nutrients postoperatively is generally acknowledged as the first choice [79] because it is theoretically more physiologic, may be associated with fewer complications and is less expensive [80]. Arguments against EN include increased risk of gastrointestinal side-effects including diarrhea and vomiting. Enteral nutrition is generally well tolerated postoperatively, and complications can usually be corrected with temporary decreases in the enteral formula infusion rate.

Studies indicate EN has advantages over PN. An early meta-analysis indicated cost benefits of EN over PN [81]. Subsequent meta-analyses confirmed this economic advantage and also indicated a decreased risk of infection associated with EN in comparison to PN [64, 82]. Studies also indicate decreased intestinal permeability and lower incidence of hyperglycemia in comparison to the PN [83]. American Society for Parenteral and Enteral Nutrition (ASPEN) guidelines recommend that perioperative EN is indicated in patients anticipated to be unable to meet nutritional needs orally for a period of 7 to 10 days whose GI tract is functional [64].

Tolerance of SNS is often an issue in oncology care. Studies indicate that the incidence of diarrhea, distention, vomiting, and other side effects is decreased [74, 77] with the use of PN when compared to EN postoperatively; however, there are some reports that contradict this [76, 78, 84].

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