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.