Acceptability and tolerance of a low tyrosine and phenylalanine diet in patients with advanced cancer - a pilot study

Background Low phenylalanine (phe) and tyrosine (tyr) diets limit tumour growth in animal models and may offer a novel cancer therapy. We studied the efficacy and acceptability of a low phe and tyr diet in patients with advanced cancer. Methods Patients with advanced metastatic melanoma (n=22) and metastatic breast cancer (n=15) were invited to follow a low phe and tyr diet (10 mg kg−1 phe and tyr per day) for 1 month. In those individuals who followed the diet for 1 month, we attempted to establish the effects on nutritional status (body weight, fat free mass, percentage body fat, serum albumin), immune cell function (white cell count, lymphocytes and neutrophils), plasma levels of phe–tyr and tryptophan and quality of life (Hospital Anxiety and Depression score). Results Only three of the 22 patients with metastatic melanoma and three of the 15 patients with metastatic breast cancer agreed to start the diet. All patients experienced problems and side‐effects and increases in anxiety and depression. There were declines in weight, with loss of fat and fat free mass but slight increases in white cell counts and neutrophils. Conclusions Low phe and tyr diets do not appear to be a viable treatment option for patients with advanced cancer.