The Fatigue of Cancer is Distinctly Different Than the Fatigue of Chronic Renal Fatigue (GP148)

Outcomes 1. Participants will be able to distinguish differences in fatigue phenotypes by using the rate of perceived effort, tapping speeds, and a fatigue scale.2. Participants will be able to appraise the difference in fatigue associated with cancer and that associated with renal failure. Key Message The location of fatigue in cancer is located upstream to the motor cortex where the fatigue of renal failure arises from the motor cortex or downstream of the motor cortex. This is determined by using tapping speed performance and rate of perceived effort with a fatigue scale. Importance There are different phenotypes of fatigue that arise from chronic illnesses. The first step to therapeutic considerations is to determine the phenotype of fatigue associated with that particular disease entity. Objective(s) Subjective fatigue in chronic illnesses may arise from different mechanisms. Fatigue may arise centrally, upstream from the motor cortex (M1), such as the supplementary motor area (SMA), from M1 due to GABA inhibitory interneurons, spinal cord Renshaw cells, to the neuromuscular junction, or from peripheral muscle. Subjective fatigue in chronic illnesses may arise from different mechanisms. Fatigue may arise centrally, upstream from the motor cortex (M1), such as the supplementary motor area (SMA), from M1 due to GABA inhibitory interneurons, spinal cord Renshaw cells, to the neuromuscular junction, or from peripheral muscle. Scientific Methods Utilized This was an exploratory project designed to capture data on the performance of the FTT by patients diagnosed with CKD. The FACIT-F assessed subjective fatigue severity. Patients were asked to complete timed tapping tasks using their dominant hand's index finger. Tapping time frames were 15, 30, and 60 seconds. Tests were repeated twice with 60 seconds of rest between each task. The effort was assessed using the Borg Rating of Perceived Exertion scale after the tapping trials. Pearson correlation coefficients were calculated to assess the relationship between fatigue, perceived effort, and tapping rate. To further examine the data, data were stratified by history of neuropathy, dialysis, ECOG scores, and rate change. R2, the variance accounted for, was included as a measure of effect size. Results A total of 30 patients consented to participate in the study. They had an average age of 73, 53% were male, and 37% had a history of peripheral neuropathy. When looking at the difference in means, those with a rate decrease had a mean FACIT-F TOI score of 6.4 points higher than those with a rate increase, indicating more significant fatigue in those with a reduced tapping rate. Similarly, the Total FACIT-F Scores were 6.6 higher in those with a tapping rate decrease than those with a rate increase. Unlike cancer patients, there was no association with RPE suggesting that the location of fatigue is from the motor cortex to the muscle. This was distinctly different from the results of the same study design used in 30 patients with cancer. In this study fatigue by the BFI correlated with the rate of perceived effort and not task failure. Conclusion(s) The neurophysiological causes of fatigue in cancer is pre-motor cortex whereas it arises from the motor cortex to muscle in those with fatigue from chronic renal failure. Impact This study provides evidence that fatigue from chronic illnesses arises from different sites within the CNS to muscle. Phenotyping fatigue within a group of chronic illnesses is the first step to developing individual therapies for each chronic illness.