Fatigue can be worse than pain for cancer patients, according to Andrea Barsevick, PhD, RN, of the Fox Chase Cancer Center in Philadelphia, Pennsylvania. Barsevick and coworkers reported that fatigue presents many challenges for researchers, doctors, and patients.
The first challenge for researchers is how to measure fatigue. Papers in the medical literature report that 25 to 99 percent of cancer patients experience fatigue. This wide range is due in part to different ways of measuring fatigue, and in part to different groups of patients being studied. An independent working group called Assessing the Symptoms of Cancer using Patient-Reported Outcomes (ASCPRO) developed a consensus definition of cancer-related fatigue as “the perception of unusual tiredness that varies in pattern of severity and has a negative impact on ability to function in people who have or have had cancer”.
Understanding the biological and genetic mechanisms of fatigue present further challenges. Barsevick identified six physiological pathways to fatigue:
1. Cytokine dysregulation
2. Hypothalamic-pituitary-adrenal axis dysfunction
3. Serotonin dysregulation
4. Circadian rhythm disruption
5. Altered ATP metabolism
6. Vagal afferent nerve activation
In addition, multiple genetic factors are associated with fatigue. These mechanisms are important for research into better treatments.
Currently available treatments are summarized in a review article by Dr. Carmen P. Escalante and Dr. Ellen F. Manzullo. Both pharmacologic and non-pharmacologic interventions are used. The stimulants methylphenidate and modafanil are the most commonly prescribed drugs for cancer-related fatigue, according to Escalante and Manzullo. Non-pharmacologic treatments include:
1. Psychosocial interventions: education, support groups, individual counseling, and coping strategies such as scheduling important activities for times when fatigue is least bothersome.
2. Exercise: aerobic conditioning, strength training, flexibility and stretching exercises, yoga, and seated exercise options. Physical exercise has the strongest evidence for effectiveness of all non-pharmacologic therapies.