The effect of a phenylalanine and tyrosine restricted diet on elemental balance studies and plasma aminograms of patients with disseminated malignant melanoma.

Previous studies indicate dietary phenylalanine and tyrosine restriction may be of value in managing advanced cancer patients. To further evaluate this approach, we performed a 60-day study in which four patients with advanced malignant melanoma received formula diets via nasogastric tube containing only 8 mg total phenylalanine and tyrosine per kg lean body mass per day. Two of three patients completing elemental balance studies were in negative nitrogen, potassium, and phosphorus balance, suggesting an essential nutrient deficiency. Three patients tolerated the diet well, but one was non-compliant. Although no serious toxicity developed, serum albumin, total iron binding capacity and cholesterol significantly decreased (p less than 0.01) in the three complaint patients. Fasting plasma phenylalanine and tyrosine values did not significantly change during the study, but two-hour postprandial plasma phenylalanine and tyrosine concentrations fell below normal and were significantly lower than preprandial levels (p less than 0.01). There were no tumor responses.