Does total parenteral nutrition (TPN) really promote tumor growth? A morphometric study

Cancer cachexia

Cancer cachexia is a complex syndrome that includes host tissue wasting, anorexia, asthenia, and abnormal host intermediary metabolism. It is present in approximately 50% of cancer patients during treatment and nearly 100% of treated cancer patients at death. Cachexia has a detrimental impact on cancer therapy. The central problem of cancer cachexia is that energy balance is not maintained, and the host has a relative hypophagia which results in host tissue wasting. The tumor by its nature and obligate growth can continue to consume glucose, amino acids, and lipids at the expense of the host. This produces abnormal host intermediary metabolism including elevated glucose production and recycling, decreased muscle protein synthesis, and increased muscle and fat breakdown. The exact mechanisms of cancer cachexia have been only partially elucidated. The identification of signal molecules like cachectin which mediate these changes may be on the horizon. Nutritional support can reverse some of the derangements seen with cachexia, and there is evidence that functional lean body mass or body cell mass can be restored in some (but not all) patients. However, nutritional support has not yet improved response to chemotherapy or radiation therapy, nor has it improved host tolerance of chemotherapy. It has improved operative mortality and morbidity in cachectic cancer patients undergoing major surgical procedures. Optimum host nutritional support appears to be dependent on high insulin concentrations in both humans and rats. Insulin and exercise may be methods to preserve host lean tissue and feed the host rather than the tumor. Future studies depend on better definition of tumor-bearing host metabolism, altering the relationship between neoplasm and host to preferentially feed the host, and making the neoplasm more susceptible to effective treatment.

Perioperative nutritional support in the cancer patient

Cancer patients in whom elective surgical intervention is planned are frequently malnourished. Moreover, the tumor itself may be responsible for additionally altering metabolism in the host, although the mechanisms by which this occurs are not clear. All preoperative cancer patients should be carefully surveyed for indices of malnutrition. Patients with a history of inadequate oral protein and calorie intake, an unintentional weight loss of greater than 10 pounds, or a serum albumin level of less than 3.5 gm per dl should undergo a thorough nutritional assessment, including anthropometric measurements, 24-hour urinary urea nitrogen and creatinine measurements, and recall skin antigen testing. Surgical risk may be predicted by using indices that are sensitive and specific in assessing preoperative parameters of malnutrition. Adequate nutritional support for 7 to 10 days prior to surgery should be provided to all patients falling into the high-risk category and has been shown to significantly reduce the rate of postoperative complications and death in this group. Generally, a serum albumin of less than 3 gm per dl, a recent unintentional weight loss of greater than 10 to 15 per cent of normal body weight, and/or skin test anergy should be considered to designate high risk. In the formulation of a nutritional plan, estimates of daily energy requirements are essential and can be made by use of the Harris-Benedict equation, metabolic cart measurements, and perhaps 24-hour urinary creatinine values. Generally, 30 to 45 kcal per kg of body weight with 1.2 to 1.5 gm of protein per kg of body weight daily, regardless of the route of delivery, will provide adequate nutritional support. Patients should be fed by the enteral route if possible. Although oral intake is preferable, many malnourished cancer patients will be unable to achieve necessary protein and calorie requirements in this manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Cancer and protein metabolism

We have reviewed the data that indicate that protein depletion is an important problem in cancer patients. An incomplete, yet useful, idea of the underlying mechanisms emerges. Further, we have seen that the provision of nutritional support may have a beneficial effect on patients with cancer, and we have explored areas of recent advances in nutritional formulation as regards energy and nitrogen source. Finally, data regarding micronutrients affecting nitrogen metabolism were reviewed. The extent to which tumor metabolism and changes secondary to the tumor-bearing state are influenced by micronutrients is not known. Traditional regimens based on the requirements of normal subjects or noncancer patients may not be relevant to the metabolic needs of the cancer patient. This could explain in part the failure of nutritional intervention trials to demonstrate a consistent benefit of nutritional support to the cancer patient. Further information regarding micronutrient needs in normal humans and cancer-bearing patients and their utilization by malignant tumors will have to be obtained.

Response of tumor-bearing rats to high-fat total parenteral nutrition

Total parenteral nutrition (TPN) solutions fed to tumor-bearing rats have been shown to affect host and tumor metabolism. This study was initiated to evaluate the effect of two intravenous nutrient regimens on carcass and organ composition as well as tumor composition and growth. Thirty Sprague-Dawley rats were implanted with Walker 256 carcinosarcoma and randomly assigned to one of three diet groups: (1) A, a glucose-based TPN formula; (2) B, a lipid-based TPN formula, isocaloric to A; and (3) C, a purified powdered diet fed ad libitum. Equal assignments were made for non-tumor-bearing controls. Tumor-bearing rats infused with diet B had the highest amount of carcass and organ fat as well as the lowest carcass and organ protein. Tumor composition paralleled carcass composition, but tumor weight and density did not differ among dietary groups. Tumor weight to body weight ratios were highest in the group fed diet B. These data indicate that although tumor growth remains unchanged, alterations in body and tumor composition are effected by a high fat TPN solution.