Cancer, cancer cachexia, and diet: lessons from clinical research.

Cachexia is a common cause of morbidity and mortality in cancer patients. Successful nutritional repletion might enhance treatment results, quality of life, and survival. In the past, attempts at nonvolitional feeding (enteral and parenteral techniques) have not been as successful as initially hoped. The cachectic cancer patient's loss of lean body mass has been very difficult to restore, although fat can be repleted. Laboratory and epidemiologic investigations have suggested that dietary calories and dietary fat may play a promotional role in cancer. Overfed animals and obese humans both have an increased tendency for development of malignancy. Breast cancer has been investigated extensively for its relationship to diet. Certain fatty acids appear to stimulate breast cancer, as do obesity-related changes in circulating hormones. Obesity in breast cancer and weight gain on adjuvant therapy may therefore be adverse prognostic signs. Clinical trials of decreasing dietary fat as an adjuvant to breast cancer therapy are in progress. The current challenge in nutritional management of the cancer patient is to incorporate laboratory, epidemiologic, and clinical data into a successful repletion strategy. It seems unlikely that traditional methods of supplying excess calories will succeed, so that other, more specific nutritional manipulations should be evaluated in clinical trials.