The expression of genes related to energy production at the cellular level changes during radiation therapy, and these changes correlate with self-reported fatigue in men undergoing treatment for prostate cancer.

Summary: This study provides evidence that genes related to mitochondrial biogenesis and bioenergetics were differentially expressed during radiation therapy, and that these changes were significantly related to changes in fatigue reported by study subjects. Changes in biochemical pathways pertinent to the maintenance of mitochondrial integrity, mitochondrial transport mechanisms, and the respiratory chain may provide some explanation of how fatigue develops in cancer patients receiving radiation therapy. 

Hsiao CP, Wang D, Kaushal A, Chen MK, Saligan L. Differential Expression of Genes Related to Mitochondrial Biogenesis and Bioenergetics in Fatigued Prostate Cancer Men Receiving External Beam Radiation Therapy. J Pain Symptom Manage. 2014 Apr 28 [epub] PMID: 24786901