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

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 5weeks 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.