Cancer-related fatigue remains poorly defined, but there is general agreement that it is multidimensional, subjective, perceived as abnormal and distressing, and inadequately relieved by rest.4, 7, 12
The National Comprehensive Cancer Network (NCCN) definition further states that cancer-related fatigue impairs usual functioning.45
The incidence of cancer-related fatigue varies with diagnosis and treatment regimens, with estimates for some disease/treatment combinations as high as 100%.46
Fatigue levels may vary within the individual patient and between individuals.47
Among the female participants in our study, almost 31% of them reported fatigue at baseline. Cancer-related fatigue leads to decreased activity which results in physiologic deconditioning, which, in turn, diminishes activity tolerance.48
The result of this downward spiral can be loss of physical function and chronic fatigue that may persist for months or even years after successful cancer treatment.11, 12, 49–51
Our findings support this association between fatigue and physical activity and between physiologic deconditioning and activity tolerance.
Adults with cancer may have disturbed sleep. In a study of 2,646 patients with cancer, 39% reported insomnia.52
Patients with cancer not only may experience decreased nighttime sleep and increased daytime sleep but may experience rapid eye movement (REM) sleep during afternoon sleep, which is considered abnormal.53
Although participants in our study had an adequate average total sleep time in 24 hours; some only had one to four hours of nighttime sleep and 19% of the 24-hour sleep total was daytime sleep.
Accurate assessment of sleep disturbance is a critical starting point for clinicians.
Polysomnography is the preferred sleep assessment modality because simply seeking a verbal report of whether patients have problems sleeping is inadequate.54
Actigraphy, a commonly used research tool based on measurement of movement and/or activity, is an objective, less costly, and less cumbersome sleep measurement device compared with polysomnography, but it cannot provide information about REM or other sleep stages and wave patterns. Neither polysomnography nor Actigraphy may be practical in everyday use by clinicians for patient care; thus, most will continue to rely on patient report via interview or questionnaires.
People with cancer may experience pain from their disease process. Fatigue, pain, and decreased functional status may be present concurrently and levels differ according to disease or treatment.55
Cancer pain may interrupt or delay sleep and increase fatigue, however pain may be mediated by sleep problems and both pain and sleep problems may mediate fatigue and lead to daytime sleepiness.56
In contrast, we found no significant correlations between sleep variables and pain. Both consistent pain and breakthrough pain may be associated with decreased function; and breakthrough pain is associated with depression.57
Our findings are similar in that fatigue, mood disturbance and performance status were moderately correlated with pain. Results using pain in our study need to be interpreted with the knowledge that our sample probably is not representative of all patients with multiple myeloma. We could not include patients with, or at high risk of, pathologic fracture and bone pain is the main source of pain with multiple myleoma. Psychosocial factors such as mood may also influence sleep and fatigue in people with cancer. In our study, baseline POMS scores indicated mood disturbance, including some very high scores. Our findings and those of others54
indicate that disturbed mood is strongly associated with fatigue severity. Depression and anxiety are associated with cancer-related fatigue, but may not predict it.58, 59
It is important for clinicians to recognize baseline mood disturbance because cancer treatment may compound mood problems. Mood changes and fatigue may result from medications used to treat MM such as thalidomide and steroids.60, 61
Patients have reported stress from steroid-related mood alterations, feeling depressed while needing to stay busy, and a desire to have less interaction with others.62
Good performance status is often one of the eligibility requirements for treatment of MM and other cancers. Patients with MM are at risk for decreased performance status at the time of diagnosis as well as during treatment. Those with low performance status may go untreated and those who are treated may face increasing performance status problems during treatment related to altered hematopoietic function and effects of medications. We found great variability in performance among participants in this study, including some individuals who were unable to walk or to lift any weight at baseline. Our findings as well as those of others indicate that performance status may be inversely associated with fatigue. 59–63
Fatigue and muscle wasting occur in 50% of patients with MM.64
Close to 100% of patients receiving intensive treatment experience fatigue. Thus, patients with MM are susceptible to virtually all treatment-associated complications that other patients with cancer experience, including cancer-related insomnia and cancer-related fatigue. Patients undergoing stem cell transplant treatment for MM are especially at high risk for developing both acute (during treatment) and chronic (post treatment) fatigue and functional deficits. 65
Research has shown that exercise can decrease patients’ fatigue and improve physical performance and psychological outlook.66–69
Individualized, moderate prescriptive exercise may lead to decreased fatigue which may then improve quality of life.70
Fatigue, mood, and functional performance may improve with a comprehensive exercise program incorporating low-to-moderate intensity aerobic and resistance exercise, education classes, and support from peers and cancer exercise program specialists.71
An individualized comprehensive exercise program may then address the holistic care needs of the patient with cancer-related fatigue, including fatigue, sleep and mood disturbances, and decreased performance status. Our analysis of baseline data from our exercise intervention study showed that fatigue, pain, sleep, mood and functional performance are interrelated. Our randomized trial of an individualized exercise program is designed to show how these variables are interrelated.