Cancer-related fatigue

Cancer-related fatigue or CRF may refer fatigue caused by cancer that begins before cancer treatment, or fatigue that begins during cancer treatment, which is also known as Post-cancer Fatigue or PCF.

Cancer-related fatigue excludes the diagnosis of chronic fatigue syndrome when symptoms can be fully accounted for by cancer-related fatigue. People with pre-existing ME/CFS may experience a significant increase in fatigue after developing cancer.

Disease process
Cancer-related fatigue and chronic fatigue syndrome have some similarities but are believed to have different underlying disease mechanisms, and affect the body differently. Fatigue can be one of several early symptoms of cancer, or may be triggered by cancer treatment. Differences include different EEG findings, different hs-CRP levels and different heart rate variability.

Symptoms
Post-exertional malaise (PEM) is increasingly regarded as the hallmark symptom in ME/CFS, but is only found in a minority of people with cancer-related fatigue.

Cancer-related fatigue was found to more closely linked to sleep quality, anxiety and depression compared to chronic fatigue syndrome.

Diagnostic criteria
Cancer-related fatigue cannot be diagnosed without a clear test indicating that cancer is present. ME/CFS is not diagnosed if an alternative explanation is present for the symptoms, such as an untreated fatiguing illness, although this does depend on the diagnostic criteria used.

Risk factors
Triggers and risk factors differ significantly between ME/CFS and cancer-related fatigue. ME/CFS is mostly commonly associated with a sudden rather than gradual onset, and often begins after an infection, particularly a virus, although many other events may trigger ME/CFS include accidents and injuries, and surgery.

Cancer-related fatigue (CRF) is associated with different demographics, for example older patients and obesity is a significant risk factor, plus the type of cancer, the cancer treatment schedule, plus specific anti-cancer drugs and treatments.

Treatment
Treatment for chronic fatigue syndrome differs significantly from the treatment of cancer-related fatigue. Exercise intolerance is a hallmark of ME/CFS and exercise therapy is linked to worsening symptoms in the vast majority of ME/CFS patients, but exercise often improves cancer-related fatigue.

Notable studies

 * 2022, Commonalities in the Features of Cancer and Chronic Fatigue Syndrome (CFS): Evidence for Stress-Induced Phenotype Instability? - (Full text)
 * 2020, Post-exertional Malaise in People With Chronic Cancer-Related Fatigue - (Full text)
 * A subset of people with chronic CRF (up to 33% in this sample) may experience PEM. Exercise specialists and health care professionals working with people with chronic CRF must be aware that PEM may be an issue. Symptom exacerbation after exercise should be monitored, and exercise should be tailored and adapted to limit the potential for harm.

Learn more

 * Spotting the difference: Cancer related fatigue vs everyday fatigue - Leukaemia Care