Fatigue During Cancer Radiation Therapy

Why you're so tired after radiation therapy

When you are prescribed radiation therapy to treat cancer, your doctor will provide you with a list of possible side effects of treatment. Things like nausea, diarrhea, and hair loss usually catch a person's attention first because they seem to be the worst. While these are side effects that can be difficult to tolerate, it is actually fatigue that affects people the most. Lack of energy and excessive tiredness seem to plague all cancer patients, but those going through radiation therapy do experience it more frequently and often chronically. Learning how to manage and cope with fatigue is essential for your quality of life during radiation therapy treatment.

man laying on a couch
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Symptoms of Fatigue

Usually a week or so after the first radiation therapy treatment you may begin to feel the following symptoms of fatigue:

  • Feeling tired or lethargic throughout the day 
  • Exhaustion (this feeling lasts longer than being tired, is more intense and isn't relieved by rest).
  • Reduced energy
  • Reduced motivation
  • Reduced concentration

Walking from the parking lot to your office may take longer and it may be difficult to accomplish physical tasks. Fatigue can be extremely frustrating because you aren't quite sleepy, but you just don't have enough energy to do much. Fatigue does affect everyone differently; some may experience mild fatigue, while others may suffer from severe chronic fatigue that considerably affects their quality of life. Your fatigue may increase over time as you undergo more radiation therapy treatments.

Why Does Radiation Therapy Cause Fatigue?

Fatigue occurs during radiation therapy because the body is working hard to repair damage to healthy cells incurred during treatment. The degree of fatigue generally varies depending on the amount of tissue irradiated, as well as the location.

But radiation therapy may not be the sole culprit of fatigue: it can be a result of cancer itself or the mental stress associated with being a cancer patient. Certain medications, such as those to prevent and treat nausea, can also be responsible for fatigue. It's impossible to pinpoint the exact cause because there are many factors in cancer treatment that can all be responsible.

6 Tips to Help Cope With Fatigue

There are many things you can do to help cope with cancer fatigue:

  • Ask for help and accept it when it is offered. Don't let pride get in the way of asking for help. Also, accept help when it is offered to you. Tasks like mowing the lawn, grocery shopping, and cleaning may be impossible when you are fatigued. Pushing yourself to accomplish everyday chores can leave you even more exhausted. Friends and family are usually happy to help—allow them to do so.
  • Get enough sleep. Getting a good night's rest is essential for everyone, not just people with cancer. If you have trouble sleeping at night, try to limit how often or how long you are napping during the day. Too much sleep can result in more fatigue and restless nighttime sleeping.
  • Rest when you need it. If you begin to feel tired, stop and take a few moments to rest to recharge your batteries. Resting can mean taking a short power nap or just sitting in a relaxing place and taking time out for yourself.
  • Ensure you are properly hydrated. Dehydration is a common cause of fatigue. Make sure you are drinking plenty of water and eating enough fruits and vegetables, which are high in water content. If you are experiencing nausea, try drinking water at room temperature—it may be easier to tolerate. Avoid caffeinated drinks; they act as a diuretic, the energy boost is short-lived, and they actually make you more tired later.
  • Think twice before drinking energy drinks. You may be tempted to drink an energy drink to give you more energy, but avoid the temptation. They are loaded with sugar and caffeine, which may give you a boost, but not enough to last the day. Like other caffeinated beverages, they may increase fatigue after you come down from the caffeine/sugar rush. 
  • Exercise when you feel you can. Studies show that exercise can increase energy in people with cancer. Exercise can be a short walk, swimming, or yoga; you don't have to hit the weights at the gym to reap the benefits of exercising.

Communicating With Your Doctor About Fatigue

Many people underestimate fatigue and fail to discuss it with their doctor. There can be underlying medical reasons for fatigue, such as anemia, that may need to be addressed. Unfortunately, there is no medication, prescription or OTC, that treats fatigue, but your doctor may be able to determine what is contributing to fatigue and offer solutions specific to your situation.

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Article Sources
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  1. Stadje R, Dornieden K, Baum E, et al. The differential diagnosis of tiredness: a systematic review. BMC Fam Pract. 2016;17(1):147. doi:10.1186/s12875-016-0545-5

  2. Dhruva A, Dodd M, Paul SM, et al. Trajectories of fatigue in patients with breast cancer before, during, and after radiation therapy. Cancer Nurs. 2010;33(3):201-12. doi:10.1097/NCC.0b013e3181c75f2a

  3. Wang XS, Woodruff JF. Cancer-related and treatment-related fatigue. Gynecol Oncol. 2015;136(3):446-52. doi:10.1016/j.ygyno.2014.10.013

Additional Reading
  • American Society of Clinical Oncology. Side Effects of Radiation Therapy. 
  • National Cancer Institute. Fatigue (PDQ). 
  • National Cancer Institute. Radiation Therapy and You.