Cancer-related fatigue is common, affecting around 9 out of 10 people with cancer.
The fatigue may be caused by the cancer itself, or the side-effects of cancer treatment.
What causes cancer-related fatigue?
Cancer treatments commonly associated with fatigue include:
- Chemotherapy. Any chemotherapy drug may cause fatigue, but it may be a more common side effect of certain drugs. Patients frequently experience fatigue after several weeks of chemotherapy but this varies among patients. In some patients, fatigue lasts a few days, while others report fatigue persisting throughout the course of treatment and continuing after the treatment is complete.
- Radiotherapy. Radiotherapy therapy can cause cumulative fatigue (fatigue that increases over time). This can occur regardless of the treatment site. Fatigue usually lasts from three to four weeks after treatment stops but can continue for up to two to three months.
- Bone marrow transplantation. This aggressive form of treatment can cause fatigue that lasts up to one year.
- Biological therapy. Interferons and interleukins are cytokines, natural cell proteins that are normally released by white blood cells in response to infection. These cytokines carry messages that regulate other elements of the immune and endocrine systems. In large amounts, these cytokines can lead to persistent fatigue.
- Combination therapy. More than one cancer treatment at the same time or one after the other increases the chances of developing fatigue.
Other factors that may contribute to cancer-related fatigue include:
- Tumour-induced hypermetabolic state. Cancer cells compete with normal cells for nutrients, often at the expense of the normal cells' growth. In addition to fatigue, weight loss and decreased appetite are common effects of this phenomenon.
- Decreased nutritionfrom the side effects of treatments (such as nausea, vomiting, mouth sores, taste changes, heartburn or diarrhoea) can cause fatigue.
- Anaemia. Cancer treatments can cause reduced blood counts, which may lead to anaemia, a blood disorder that occurs when there is not enough haemoglobin in the blood. Haemoglobin is a substance in the red blood cells that enables the blood to transport oxygen through the body. When the blood can't transport enough oxygen to the body, fatigue can result.
- Hypothyroidism. If the thyroid gland is under-active (hypothyroidism), metabolism may slow down so that the body does not burn food fast enough to provide adequate energy. This is a common condition in general, but may happen after radiotherapy to the lymph nodes in the neck.
- Medication. Medication used to treat side effects such as nausea, pain, depression, anxiety and seizures can cause fatigue.
- Pain. Research shows that chronic, severe pain increases fatigue.
- Stress. Stress can worsen feelings of fatigue. Stress can result from dealing with the disease and the "unknowns," as well as from worrying about daily accomplishments or trying to meet the expectations of others.
- Overworking yourself. Fatigue may result when patients try to maintain their normal daily routines and activities during treatments. Modification may be necessary in order to conserve energy.
- Depression. Depression and fatigue often go hand-in-hand. It may not be clear which started first. One way to sort this out is to try to understand your depressed feelings and how they affect your life. If you are depressed all the time, were depressed before your cancer diagnosis, are preoccupied with feeling worthless and useless, you may need treatment for depression.