What is fatigue? How does it affect cancer patients?
Risk factors: In the setting of cancer, fatigue may be caused by the type of cancer and its stage, chemotherapy or radiation therapy, stress, anemia, depression, chronic pain, lack of sleep, lack of proper nutrition, nausea and vomiting, infections, dehydration and electrolyte imbalance, and weight loss.
Etiology and the disease process: The causes of fatigue in patients with cancer are not clearly understood and appear to be multiple. Fatigue can be one of the first symptoms of the presence of cancer and can also be an indication of disease progression. The disease of cancer itself can cause fatigue, primarily through the release of cytokines, which are thought to induce fatigue, the increased need of cancer cells to maintain their high rate of metabolism, and the alteration of hormone levels. The stress of having cancer also can be the cause of fatigue. Treatments can lead to fatigue as the body tries to deal with the insult of cytotoxins or radiation and tries to rebuild cells after treatment. Many biological therapies (those that attempt to strengthen the patient’s immune system to fight cancer) have flu–like symptoms, including fatigue, as side effects. Medication used as supportive care (for example, to treat depression or vomiting) can cause fatigue. Another cause of fatigue is lack of sleep, which may be caused by pain, emotional issues, depression, and anxiety. Poor nutrition, caused by lack of interest in food or an inability to eat because of mucositis, diarrhea, nausea, or vomiting, has been implicated in fatigue. Surgery for cancer may be the cause of fatigue, which often lessens as the patient recuperates and heals. One way that cancer can cause fatigue is by spreading to bone marrow, where it destroys red blood cell production and leads to anemia, the most commonly reported cause of fatigue. Both chemotherapy and radiation therapy can destroy bone marrow and cause anemia.
Incidence: Depending on the type of cancer and its treatment, approximately 14 to 96 percent of patients with cancer report feeling mentally and physically fatigued during the course of treatment while 19 to 82 percent of patients report cancer-related fatigue following treatment, according to the National Cancer Institute's 2014 estimates.
Symptoms: Fatigue is manifested by extreme tiredness and inability to perform normal daily functions. Fatigue can then lead to other symptoms, such as depression or poor nutrition (if the patient is unable to shop for groceries or cook). Because of the nature of cancer-related fatigue and its interactions with risk factors and other conditions, it is difficult to pinpoint a single symptom. Common symptoms, however, can include dizziness, confusion, inability to think clearly, loss of balance, being bedridden for more than one day, and worsening conditions (for example, increased vomiting, pain, or depression).
Screening and diagnosis: Because of the complex nature of cancer-related fatigue and its many presumptive causes, it is necessary to carefully rule out causes before effective treatment can occur. It is imperative to understand the pattern of fatigue, including when it started, how long it lasted, and how it changed the patient’s daily activity pattern. If fatigue was reported only after radiation therapy, for example, depression and other medications could be ruled out as the cause. The kind of cancer and its stage is important to know, as are known treatment-related symptoms. The side effects of chemotherapeutic agents or other medications may be instructive in determining the cause of fatigue. The health care provider should understand the patient’s sleep patterns before starting treatment for cancer as well as during treatment for cancer. It is important to know if the patient’s eating habits have changed. Patients should be screened for depression, as this is a common cause of fatigue. Patients may be depressed because of their cancer or because they fear losing their jobs, are having financial difficulties, or are upset about their inability to perform their normal daily activities.
Anemia, which is a common cause of fatigue, can be determined through blood tests. Depression scores can be determined through the use of various screens. No staging is available, however, for grading cancer-related fatigue.
Treatment and therapy: To be treated properly, the source of fatigue whether is it physical, emotional, or psychological must be determined. Because anemia is the most common cause of fatigue, blood tests generally are done to check for low red blood cell counts, low hemoglobin concentration, or both. Anemia can be corrected by blood transfusions. After a focused review, in 2010 the US Food and Drug Administration approved a new risk management program and demanded updated warnings and revised dosing instructions for the use of erythropoiesis-stimulating agents (ESAs) in the treatment of anemia as these agents were found to decrease survival and/or augment the chance of tumor development or reappearance in patients with several types of cancer.
Fatigue due to lack of sleep, depression, or poor nutrition generally can be helped by administration of supportive care, such as drugs, or correction of an underlying cause, such as the inability to shop for and prepare food.
Patients may be able to help themselves by being aware of what causes their fatigue. It may be important to schedule regular naps or limit the number of visitors. It is important to save energy for important tasks and to ask for help with other tasks. Energy levels may be maintained by scheduling regular eating times, including healthy snacks, limiting caffeine and alcohol, and drinking increased amounts of fluids. Some patients report that mild to moderate exercise also helps fight cancer-related fatigue, allows for a better frame of mind, and increases the ability to sleep at night. Exercise can include aerobic or resistance training. Relief of cancer-related fatigue may also come from practicing yoga or meditation. Research suggests that psychosocial interventions, such as group or individual therapy, education, stress management, or support groups, also have a positive effect on cancer-related fatigue.
Prognosis, prevention, and outcomes: Because cancer-related fatigue is often caused by many overlapping factors, it is difficult to predict which patients will be most affected. Fatigue may subside once treatments are completed and the patient’s bone marrow has recovered. Fatigue may increase as the cancer stage progresses and the cancer spreads in the body.
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