Cancer Treatment-Related Fatigue: Psychometric Testing of the Cancer Treatment-Related Fatigue Representation Scale (CTRFRep) in Patients Undergoing Radiation Treatment for Cancer

Abstract

Cancer treatment-related fatigue (CTRF) is recognized as a prevalent and bothersome symptom for patients with cancer. In a model of the CTRF experience, CTRF representation, or the beliefs, thoughts and emotions surrounding the experience of CTRF, is believed to mediate the relationship between CTRF intensity and CTRF distress. To date, there is no reported measure of CTRF representation. The purpose of this descriptive, cross-sectional study guided by Leventhal’s Common Sense Model of Self-Regulation was to evaluate an instrument designed to measure CTRF representation, the CTRF Representation scale (CTRFRep), based on an existing measure, the Illness Perception Questionnaire (IPQ-R). The study included 47 patients (mean age=57.7 years) receiving radiation therapy for cancer interviewed one month post-treatment. 77% of patients had fatigue during treatment. Three content experts and one theory expert assessed content validity of the CTRFRep. The content experts included three behavioral oncology nurse researchers whose focus is on symptom management and/or fatigue. The theory expert was a nurse researcher who is an expert in the area of self-regulation theory. As tested, the CTRFRep consisted of 105 items in 10 subscales addressing beliefs about the Identity, Timeline (Acute vs. Chronic/Cyclical), Consequences (positive/negative), Cause, Control (Treatment/Personal), Symptom Coherence, and Emotional Representation of CTRF. When evaluating psychometrics, the Identity and Cause subscales are analyzed independent of the other subscales. For the Identity subscale, symptoms most reported as related to CTRF were lack of energy, loss of strength, and feeling blue. For the Cause subscale, the most common beliefs regarding causes of CTRF were cancer treatment(s), having cancer, and stress or worry. Results indicate adequate reliability in six of eight remaining subscales (α>=0.70); the item N in those subscales was reduced from 56 to 34. To address construct validity, logistic regression assessed whether CTRFRep mediated the relationship between CTRF intensity and CTRF distress. After controlling for negative affect, the Identity and Consequences subscales were significant mediators – the Acute vs. Chronic Timeline and Emotional Representation scales were partial mediators – of the relationship between CTRF intensity on CTRF distress. These findings indicate fatigue is a problem for people undergoing treatment for cancer, and the CTRFRep may be a reliable and valid measure of CTRF representation for patients undergoing radiation treatment for cancer. Small sample size prevented successful factor analysis of the CTRFRep. Further research of the CTRFRep is warranted.