Altered amino acid homeostasis and the development of fatigue by breast cancer radiotherapy patients: A pilot study.

Abstract Objectives To examine altered amino acid homeostasis as a predisposing factor of fatigue in female radiotherapy breast cancer patients. Design and methods Participants underwent breast-conserving surgery and adjuvant breast irradiation and were free from significant fatigue pre-radiotherapy. The Functional Assessment of Cancer Therapy fatigue subscale was used to assess fatigue pre- and post-radiotherapy. Blood biochemistry factors and urinary and plasma amino acid levels were measured. Results One third of 27 patients developed fatigue and were designated as the fatigued cohort. It was possible to differentiate between fatigued subjects pre- and post-radiotherapy based upon their urinary amino acid profiles. Univariate analysis supported altered amino acid homeostasis within the fatigued cohort. Urinary levels of histidine and alanine were increased pre-radiotherapy whilst threonine, methionine, alanine, serine, asparagine and glutamine levels were higher after 5 weeks of radiotherapy for the fatigued cohort. Conclusions Fatigue was accompanied by altered amino acid homeostasis with increased amino acid excretion suggestive of a catabolic response.