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.
3. Sleep therapy: some patients benefit from behavioral changes such as a low-stimulus environment before bedtime.
4. Acupuncture: this has not been well studied, but small trials suggest possible benefit.
Escalante and Manzullo reported that many cancer patients and survivors are reluctant to mention fatigue as a symptom. Physicians also tend to place low priority on asking about fatigue. Thus, both patients and their doctors are encouraged to discuss this important symptom.
References:
1. Barsevick A et al, “I'm so tired: Biological and genetic mechanisms of cancer-related fatigue”, Qual Life Res. 2010 December; 19(10): 1419-27.
2. Escalante CP et al, “Cancer-related fatigue: The approach and treatment”, J Gen intern Med 2009; 24(Suppl 2): 412-6.
Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.