Before treatment starts, many people already feel tired from the tests and investigations used to diagnose the cancer. The cancer itself can also make you feel tired. They may also be tired from trying to cope with different emotional effects. People who are older, have other medical problems, or have more than one type of treatment are more likely to be affected by cancer related fatigue.
Many people feel tired after surgery and need to take things easy for a while. This effect is usually temporary. However, some types of surgery may cause continuing problems with fatigue. For example, surgery to the stomach may lead to problems with absorbing food. If you are unable to absorb nutrients from food this can affect your energy levels.
Chemotherapy and radiotherapy
Chemotherapy is the use of anti-cancer (cytotoxic) drugs to destroy cancer cells. It is often given in cycles a few weeks apart. Some people feel most fatigued in the first few days after chemotherapy and then find it gets better until the next cycle. The fatigue may increase with each round of treatment.
Radiotherapy treats cancer by using high-energy rays to destroy cancer cells. Often people may feel increasingly fatigued as the treatment goes on.
Fatigue caused by chemotherapy or radiotherapy usually improves after treatment, but sometimes it can be more of a long term problem.
Many people find their normal levels of energy return within 6–12 months of the treatment ending. However, some people find they still feel tired and have low energy levels a year or so later. Sometimes, tiredness can continue for two years or more, although this is far less common.
Hormonal therapies are treatments that can stop or slow the growth of some cancer cells. They either alter the levels of particular hormones in the body or prevent the hormones from being absorbed by cancer cells. These are often given for several years. Some hormonal therapies can cause fatigue.
Targeted (biological) therapies
Targeted therapies use substances that target the growth of cancer cells. Some of them can cause fatigue.
Apart from treatment related anaemia, doctors are still trying to find out exactly why cancer treatments cause fatigue. It’s thought that fatigue may occur after having cancer treatment because:
- the body needs extra energy to repair and heal
- there is a build-up of chemicals as the cancer cells are destroyed
- the body’s immune system is affected.