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Side effects of radiation therapy

Radiation therapy damages cancer cells but can also damage healthy cells in the treatment area. Damage to healthy cells causes side effects. Side effects depend on what part of the body receives radiation therapy. Different cells and tissues in the body cope differently with radiation. Rapidly dividing cells are affected the most. These include skin cells, cells lining the mouth and gastrointestinal (GI) tract and blood cells in the bone marrow.

Side effects can happen any time during, immediately after or a few days or weeks after radiation therapy. Most side effects generally go away within a few weeks to 2 months of finishing treatment. But some side effects may continue after treatment is over because it takes time for healthy cells to recover from the effects of radiation therapy. Late side effects can happen months or years after treatment. If doses of radiation are high enough, some cells may not be able to repair themselves. As a result, some side effects may last a long time or be permanent.

In general, the side effects of radiation therapy will depend on:

  • the type of radiation therapy
  • the part of your body being treated
  • the amount (dose) of radiation and treatment schedule
  • your overall health

General side effects of radiation therapy

Fatigue is one of the most common side effects of radiation therapy. It usually happens after a few weeks of radiation therapy and can get worse as treatment goes on. It can be caused by a number of things. During radiation therapy, your body uses more energy to heal itself. Fatigue is more common when larger areas of the body are treated. Radiation therapy to areas of bone marrow, such as the pelvis can cause anemia. Anemia can cause fatigue. Problems eating or sleeping can make fatigue worse. Changes to your schedule such as daily trips to the hospital can also make you feel tired. Fatigue usually goes away gradually after treatment has ended, but some people continue to feel tired for several weeks or months after radiation therapy.

Skin problems are common with external radiation therapy because the radiation travels through the skin to reach the area being targeted for treatment. The skin in the radiated area may become red, dry or itchy. It may change colour (become darker or tanned looking). Most skin reactions happen within the first 2 weeks of starting radiation therapy. They usually go away a few weeks after treatment, but some skin changes, like skin darkening or scarring, can be permanent. Some people do not experience any skin reactions with radiation therapy.

Hair loss (alopecia) or thinning of hair only happens in the area being treated with radiation therapy. How much hair loss you have and regrowth varies from person to person and depends on the dose of radiation. Hair loss can begin about 2 to 3 weeks after radiation therapy starts. Smaller doses of radiation usually result in temporary hair loss. Permanent hair loss is more common at higher doses. When hair regrows, usually about 3 to 6 months after radiation therapy is finished, the colour or texture may be different and it may grow back thinner or patchy.

Loss of appetite can start within the first few weeks of radiation therapy and can continue after treatment has ended. Side effects like sore mouth, dry mouth, problems swallowing and nausea and vomiting can cause loss of appetite. Radiation therapy to the head and neck area can cause temporary changes in taste or smell, which can make foods seem less appetizing. Some people lose interest in food completely and don’t eat, even though they know they need to. Maintaining good nutrition during and after radiation therapy is important to help a person recover from treatment.

Nausea and vomiting can be a common side effect of external radiation therapy, especially if the treatment area includes the stomach and abdomen. It can also happen as a general side effect regardless of the area being treated. Radiation sickness usually goes away a few weeks after radiation therapy is finished.

Low blood cell counts happen because of radiation’s effect on blood cells made in the bone marrow. Low blood cell counts are more common if you receive chemotherapy at the same time as radiation therapy or if the treatment area includes the pelvic bones (where many blood cells are made). Low blood cell counts are usually not severe enough to cause problems. When there is a break from treatment for a few days, blood cell counts usually recover.

Side effects of radiation to the brain

Stereotactic radiosurgery (SRS) focuses a high dose of radiation on one small area in the brain. Side effects will depend on the area where radiation therapy is given. Sometimes the whole brain is treated with radiation, although the doses are often lower. High doses of radiation therapy to the brain are more likely to cause long-term problems. In children, the younger the child, the more sensitive the brain cells are to the side effects of radiation.

Side effects of radiation therapy to the brain may include:

Side effects of radiation to the head and neck

Radiation therapy can irritate the mucous membranes lining the mouth, throat and upper part of the esophagus. It can also affect other structures in the treatment area.

Side effects of radiation therapy to the head and neck may include:

  • skin problems
  • hair loss
  • sore mouth
  • dry mouth
  • taste changes
  • difficulty swallowing
  • earaches or difficulty hearing if the ear is in the treatment area
  • changes to the voice, such as hoarseness, if the voice box (larynx) is in the treatment area
  • vision changes if the radiation damages any blood vessels of the eye or the optic nerve
  • dry eyes and vision loss if radiation involves the eyes
  • stiff jaw (trismus) if radiation involves the jaw
  • loss of appetite
  • dental problems such as tooth decay
  • nausea and vomiting
  • hormone problems – low levels of hormones can be a late side effect of radiation therapy to the hypothalamus, pituitary gland or thyroid
  • nerve damage if radiation therapy damages any of the cranial nerves causing vision changes, hearing problems or weakness of the face, tongue, neck or shoulder
  • death of bone from radiation (caused osteoradionecrosis)

Side effects of radiation to the chest

Radiation therapy to treat lymphoma and cancers of the lung, esophagus, spinal cord and breast is often directed at structures within the chest. Radiation to the upper part of the chest can irritate the throat and esophagus.

Side effects of radiation therapy to the chest may include:

Side effects of radiation to the abdomen

Radiation therapy to the upper abdomen can irritate the esophagus and stomach. Radiation to the lower abdomen is more likely to irritate the small and large intestines. People are more likely to experience side effects if a large part of the abdomen is treated.

Side effects of radiation to the abdomen may include:

Side effects of radiation to the pelvis

Radiation therapy to the pelvis can irritate the large and small intestines and cause digestive problems. It can also irritate the bladder and affect the reproductive organs.

Side effects of radiation to the pelvis may include:

Late side effects

Late side effects can appear a long time after treatment finishes and can be different depending on where on your body you had radiation therapy. Some possible late effects are:

  • fertility problems (if you had radiation therapy to the pelvis)
  • heart problems (if you had radiation to the chest)
  • lung problems (if you had radiation to the chest)
  • changes in skin colour
  • mental or emotional problems (if you had radiation to the head and neck or brain)
  • osteoporosis
  • second cancers

gastrointestinal (GI)

Referring to or having to do with the digestive organs.

The gastrointestinal (GI) tract, or digestive tract, includes the mouth, pharynx (throat), esophagus, stomach, small intestine and large intestine.

somnolence syndrome

A group of symptoms that include drowsiness, lethargy (abnormal drowsiness or lack of energy), loss of appetite and irritability.

Somnolence syndrome can occur in children following radiation therapy to the head.

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