Fatigue and dyspnea are two of the most common symptoms associated with advanced cancer. Fatigue is also commonly associated with cancer treatment and occurs in up to 90% of patients undergoing chemotherapy. Both symptoms have many possible underlying causes. In most patients, the etiology of fatigue or dyspnea is multifactorial, with many contributing interrelated abnormalities. In one study of patients with advanced cancer, fatigue was found to be significantly correlated with the intensity of dyspnea. This chapter will discuss the mechanisms, clinical features, assessment, and management of both of these troublesome and often undertreated symptoms in cancer patients.
Cancer-related fatigue is defined by the National Comprehensive Cancer Network (NCCN) as "a distressing, persistent, subjective sense of physical, emotional, and/or cognitive tiredness or exhaustion related to cancer or cancer treatment that is not proportional to recent activity and interferes with usual functioning." In cancer patients, fatigue is often severe; has a marked anticipatory component; and results in lack of energy, malaise, lethargy, and diminished mental functioning that profoundly impairs quality of life. It may be present early in the course of the illness, may be exacerbated by treatments, and is present in almost all patients with advanced cancer.
Fatigue is sometimes referred to as asthenia, tiredness, lack of energy, weakness, and exhaustion. Not all of these terms have the same meaning to all patient populations. Moreover, different studies of fatigue and asthenia have looked at different outcomes, ranging from physical performance to the purely subjective sensation.
The mechanisms of cancer-related fatigue are not well understood. Substances produced by the tumor are postulated to induce fatigue. Blood from a fatigued subject when injected into a rested subject has produced manifestations of fatigue. The host production of cytokines in response to the tumor can also have a direct fatigue-inducing effect. Muscular or neuromuscular junction abnormalities are a possible cause of chemotherapy- or radiotherapy-induced fatigue. In summary, fatigue is the result of many syndromes—not just one. Multiple mechanisms are involved in causing fatigue in most patients with advanced cancer.
The causes of fatigue in an individual patient are often multiple, with many interrelated factors. Figure 1 summarizes the main contributors to fatigue in cancer patients.
Cancer cachexia results from a complex interaction of host and tumor products. Host cytokines such as tumor necrosis factor, interleukin-1 (IL-1), and IL-6 are capable of causing decreased food intake, loss of body weight, a decrease in synthesis of both lipids and proteins, and increased lipolysis. The metabolic abnormalities involved in the production of cachexia and the loss of muscle mass resulting from progressive cachexia may cause profound weakness and fatigue. However, many abnormalities described in Figure 1 are capable of causing profound fatigue in the absence of significant weight loss.
Decreased physical activity has been shown to cause deconditioning and decreased endurance to both exercise and normal activities of daily living. On the other hand, overexertion is a frequent cause of fatigue in noncancer patients. It should also be considered in younger cancer patients who are undergoing aggressive antineoplastic treatments such as radiation therapy and chemotherapy and who are nevertheless trying to maintain their social and professional activities.
In patients without cancer who present with fatigue, the final diagnosis is psychological (eg, depression, anxiety, and other psychological disorders) in almost 75% of patients. The frequency of major psychiatric disorders in cancer patients is low. However, symptoms of psychological distress or adjustment disorders with depressive or anxious moods are much more frequent. Patients with an adjustment disorder or a major depressive disorder can have fatigue as their most prevalent symptom.
Low red blood cell count related to advanced cancer or chemotherapy has been associated with fatigue, and its treatment results in improvement of fatigue and quality of life in these patients. In terminally ill patients with advanced cancer, treatment of anemia may not resolve fatigue adequately due to the multifactorial nature of its etiology. Fatigue may be the result of the more intense nature of the other contributory factors.
Autonomic insufficiency is a frequent complication of advanced cancer. Autonomic failure has also been documented in patients with a subset of severe chronic fatigue syndrome. Although the association between fatigue and autonomic dysfunction has not been established in cancer patients, it should be suspected in patients with severe postural hypotension or other signs of autonomic failure.
Both intrathecal and systemic opioid therapies, as well as cachexia and some antineoplastic therapies, can result in hypogonadotropic hypogonadism. This condition can lead to fatigue, depression, and reduced libido.
Chemotherapy and radiotherapy treatments are common causes of fatigue in cancer patients. The pattern of fatigue reported by patients with cancer who receive myelosuppressive chemotherapy is cyclical. It begins within the first few days after therapy is started, peaks around the time of the white blood cell nadir, and diminishes in the week thereafter, only to recur again with the next cycle of chemotherapy. Fatigue tends to worsen with subsequent cycles of chemotherapy, which suggests a cumulative dose-related toxic effect. Compared with women with no history of cancer, former patients with breast cancer who had received adjuvant chemotherapy reported more fatigue and worse quality of life due to this symptom. Similar results have been noted in breast cancer patients who have been treated with high-dose chemotherapy and autologous stem-cell support and in patients treated for lymphoma.
Radiation therapy tends to cause a different pattern of fatigue. It is often described as a "wave" that starts abruptly within a few hours after treatment and subsides shortly thereafter. Fatigue has been noted to decrease in the first 2 weeks after localized treatment for breast cancer but then to increase as radiation therapy persists into week 4. It then decreases again 3 weeks after radiation therapy ceases. The mechanism for fatigue in these situations is not well understood.
Administration of chemotherapy and radiotherapy for malignancy causes a specific fatigue syndrome. Combined therapy with the two modalities appears to cause worse fatigue than does either modality given alone.
Surgery is another common cause of fatigue in patients with cancer. In addition, commonly used medications such as opioids and hypnotics may cause sedation and fatigue.
Comorbid conditions not necessarily related to cancer, such as renal failure or congestive heart failure, may coexist and contribute to the problem. Other conditions include the chronic stress response (possibly mediated through the hypothalamic-pituitary axis), disrupted sleep or circadian rhythms, and hormonal changes (eg, premature menopause and androgen blockade secondary to cancer treatment).
Since fatigue is essentially a subjective sensation, it is by nature difficult to assess. There is agreement that self-assessment should be the "gold standard." Due to the complex nature of the symptoms of fatigue, an effort to identify a set of diagnostic criteria similar to those for depression has been attempted. This syndromal approach has been useful to assess the presence or absence of the clinical syndrome of fatigue.
Table 1 summarizes the four most common measurable indices to assess fatigue. The first category in Table 1 looks at the objective function that the patient is capable of performing when subjected to a standard task. These functional tasks have limited value in cancer care, however, as they are very difficult for the advanced cancer patient to perform.
The second category in Table 1 attempts to assess the subjective effects of standard tasks.
The third category in Table 1 has been the most commonly used in oncology. The two most common scales, ECOG (Eastern Cooperative Oncology Group) and Karnofsky Performance Status, consist of a physician's rating of the patient's functional capabilities after a regular medical consultation. A physical therapist completes the Edmonton Functional Assessment Tool and attempts to determine the functional status, as well as all the obstacles to clinical performance, of these patients.
The fourth category in Table 1 is the most relevant for both clinical management and clinical trials in fatigue. Visual analog scales, numerical scales, the Brief Fatigue Inventory, and the Piper Fatigue Self-Report Scale have been validated. In addition, there are validated functional assessments in most quality-of-life questionnaires.
In addition to the assessment of the intensity of fatigue, the clinical assessment of these patients requires clinicians to determine the impact of all factors on the presence of fatigue.
To treat fatigue optimally, it is vital to identify and prioritize the different underlying factors in the individual patient. Thorough records, including recent treatment history, physical examination, and medication review, in addition to simple laboratory investigations, will help identify possible underlying causes. Figure 2 outlines a therapeutic approach to fatigue management in cancer patients. Whenever possible, an attempt should be made to treat these contributing factors. It is impossible to be certain whether one of these identified problems is a major contributor to fatigue or simply a coexisting problem in a given patient. Therefore, it is of great importance to measure the intensity of fatigue and the patient's performance before and after treating any contributing factor. If the level of fatigue does not improve after correction of these abnormalities, it is clear then that further treatment will not result in improvement in the future.
In patients with cancer treatment–related fatigue, it is important to exclude specific causes, such as hypothyroidism, hypogonadism, and anemia, and to consider other potential adverse effects of treatment. If specific problems are identified, they should be appropriately managed. For instance, patients with anemia may experience symptomatic improvement with the administration of erythropoietic therapy (epoetin alfa [Epogen, Procrit] and darbepoetin alfa(Drug information on darbepoetin alfa) [Aranesp]) at the dose and administration schedule that best fit the patient's need. Epoetin alfa(Drug information on epoetin alfa) may be administered weekly by subcutaneous injection; darbepoetin alfa has a longer half-life, requiring less-frequent dosing. Dosages and schedules of both agents may be increased if necessary. (For up-to-date information about the safety and use of erythropoiesis-stimulating agents from the US Food and Drug Administration (FDA) visit the "Information on Erythropoiesis-Stimulating Agents (ESA), Epoetin alfa (marketed as Procrit, Epogen), Darbepoetin alfa (marketed as Aranesp)" page on the FDA's Web site.
In most patients, there will be no identified reversible causes. A number of effective pharmacologic and nonpharmacologic symptomatic treatments are available for these patients.
Corticosteroids. There is substantial evidence that corticosteroids can reduce fatigue and other symptoms in cancer patients. They are probably best retained for short-term use. Their beneficial effects generally last between 2 and 4 weeks, and longer-term use carries the risk of serious adverse effects. Most studies have used the equivalent of 40 mg/d of prednisone(Drug information on prednisone).
Progestational agents. In recent studies of terminally ill patients, megestrol (60–480 mg/d) has been shown to have a rapid (less than 1 week) beneficial effect on appetite, fatigue, and general well-being.
Psychostimulants. Psychostimulants (eg, methylphenidate(Drug information on methylphenidate), 5–10 mg in the morning and at noon or 5 mg as needed) may be useful in treating fatigue in patients with advanced cancer. The safety and efficacy of long-term methylphenidate use for fatigue have not been established. Recently, Morrow et al found modafinil(Drug information on modafinil) (Provigil) therapy to be beneficial in mitigating fatigue, especially when used in cancer patients with severe baseline fatigue who were on cytotoxic therapy.
In addition to these agents, a number of other drugs have been tried in preliminary studies in patients with fatigue.
In a recent double-blind, randomized, controlled trial by the North Central Cancer Treatment Group (NCCTG), 282 patients with cancer reported improvement of cancer-related fatigue when treated with American ginseng (Panax quinquefolius) vs placebo.
In a randomized, controlled study of 142 patients with advanced cancer conducted by Bruera et al, donepezil(Drug information on donepezil) (Aricept) was not significantly superior to placebo in the treatment of cancer-related fatigue.
Segal et al studied the effect of exercise on the fatigue experienced by prostate cancer patients receiving radiation therapy. Among the 121 patients, over a period of 24 weeks, 40 patients initiating radiotherapy with or without androgen deprivation took part in resistance exercise, 40 participated in aerobic exercise, and 41 received usual care. Results of the Functional Assessment of Chronic Illness Therapy–Fatigue (FACIT-F) subscale showed that compared with usual care, resistance exercise resulted in both short- and long-term improvement in fatigue and aerobic exercise resulted in short-term improvement.
Physical therapy and occupational therapy. Physical therapy may encourage increased activity, where appropriate, and provide active range of motion to prevent painful tendon retraction. Recent evidence suggests that exercise (aerobic and resistance) may reduce fatigue during chemotherapy. Assessment of the home environment by an occupational therapist can be useful. The provision of ramps, walkers, wheelchairs, elevated toilets, and hospital beds may allow the patient to remain at home in a safe environment. Education regarding the pattern of fatigue during treatment has been helpful. Counseling (more specifically, cognitive behavioral therapy) for stress management, depression, and anxiety may reduce distress and fatigue as well as improve mood.
A recent controlled trial by Cohen et al assessed 163 breast cancer patients receiving radiation therapy who were randomized to a yoga group, a stretching group, or a waitlist group. Patients assigned to yoga for three 1-hour sessions a week for 6 weeks during radiation therapy showed improvement in fatigue (Brief Fatigue Inventory Scale [BFI] scores, 0.23), as did the stretching group (BFI, 0.45). However, patients in the yoga group had a greater improvement in physical functioning (SF-36 [Short Form 36 Health Survey]), compared with the stretching and waitlist groups.