Radiation therapy is commonly used to treat brain cancer. Its goal is to destroy cancer cells and shrink tumors. It’s often used alongside other treatments, such as surgery or chemotherapy.

When radiation damages healthy cells, it can cause some unwanted side effects. Specific side effects vary between people based on factors around your treatment and overall health.

In this article, we break down the side effects of radiation therapy for brain cancer. We also look at how radiation therapy is used to treat cancer and how to manage these side effects.

Radiation therapy is used to shrink tumors and slow the growth of brain cancer. It’s often used together with chemotherapy or surgery to give doctors the best chance of completely removing the tumor. It’s also used for people who aren’t able to undergo surgery.

Radiation therapy uses high doses of radiation to kill cancer cells by damaging their DNA. Radiation is concentrated beams of energy. It’s also used in X-rays in lower doses to produce an image of the inside of your body. When the DNA of cancer cells is damaged, the cells are unable to divide or grow and eventually die.

However, radiation therapy also damages the DNA of healthy cells around the part of your body where radiation is delivered. It’s especially prone to damaging rapidly growing cells such as stem cells.

Stem cells have the potential to become any other type of cell. When these are damaged, your body is unable to create new cells to replace the cells in your body when they die — at least temporarily. Not replacing these cells may cause you to develop side effects that usually pass after 2 to 3 weeks.

Radiation therapy can cause side effects due to damage to healthy brain tissue and cells around your head and neck. The goal is to deliver the lowest possible effective dose of radiation to minimize damage to healthy brain tissue.

Some side effects appear shortly after treatment while others may not occur for months or years.

Early side effects usually appear within a few weeks of treatment and pass within 3 weeks.

Fatigue and mood changes

Fatigue and mood changes are among the most common side effects of radiation therapy.

Fatigue has been reported in up to 90 percent of people with cancer treated with radiation. Many people undergoing radiation therapy find they need to prioritize rest or take time off from work. Fatigue is different from a feeling of tiredness, and it may build over time as you continue radiation treatment.

Scheduling time throughout the day for naps and exercising regularly are two strategies that may help you deal with your fatigue.

Many people find they may have more energy at certain times of day, so you may want to take this into account when planning your day.

Fatigue may last up to a year after treatment.

Mood changes may include irritability, depression, and anxiety. Hormonal imbalances caused by radiation therapy and psychological factors can both play a role in the development of mood changes.

Hair loss

Many people who receive radiation lose a noticeable amount of hair.

A recent study found that 75 to 100 percent of people develop noticeable hair loss on their scalp after receiving radiation greater than 2 gray (Gy), which is a low dose. The study found that 50 percent of people with cancer treated with 36.1 Gy of radiation experience severe hair loss.

Hair loss generally starts 2 to 3 weeks after starting radiation therapy.

The American Cancer Association notes that hair often grows back within 3 to 6 months after radiation treatment is finished.

Nausea and vomiting

About 50 to 80 percent of people undergoing traditional radiation therapy develop nausea and vomiting during or after treatment. Nausea may come in waves and may appear before vomiting.

Several types of medication can help treat nausea and vomiting, including corticosteroids. You can work with your doctor to find the treatment that is right for you.

Skin changes

Approximately 85 percent of people undergoing modern radiation therapy experience moderate to severe skin reactions around the treatment area. Some people develop dry and peeling patches of skin, while others develop skin that looks sunburned, puffy, red, or swollen.

Severe reactions may include blistering, skin loss, and ulcers. It’s fairly common to develop sores in your mouth.

If you develop severe skin reactions, your doctor may adjust your radiation dosage.


Radiation therapy can cause swelling of the brain that causes headaches. Headaches are a less common side effect than fatigue or irritability but can affect your quality of life. There are several medications that can help the pain from these headaches. Your doctor may also recommend steroids to address headaches.

If you experience new or worsening headaches, it’s important to let your doctor know. You can work together to find the right medication for your symptoms.

Vision changes

Some people develop blurry vision or other vision changes because of damage to cells in the eyes or optic nerve. Vision changes due to damage to the optic nerve is a rare side effect but can seriously impact your vision. It’s important to immediately report any visual changes to your doctor.

Radiation necrosis

Radiation necrosis is a rare side effect where a lump of dead tissue forms at the tumor site months or years after the initial treatment. It can often be managed with corticosteroids, but in some cases, you may need surgery.

Increased risk of another brain tumor

Radiation can damage the DNA of your healthy cells, increasing your chances of developing cancer in your brain, surrounding tissue, or skull. The risk is small, and when it happens, tumors usually occur years after radiation.

Memory and cognitive changes

If large areas of your brain become damaged, you can potentially develop cognitive changes, such as:

  • problems concentrating
  • personality changes
  • memory loss
  • specific symptoms to the part of your brain damaged
  • hormonal imbalances


Swelling of your brain due to radiation can lead to seizures. If you develop new or worsening seizures, it’s important to contact your doctor as soon as possible.

Tips for coping with radiation side effects

Radiation side effects vary but can impact your quality of life. Here are some general ways you can manage your side effects at home:

  • Prioritize getting plenty of rest.
  • Eat a healthy and balanced diet.
  • If you lose your taste or appetite, you may want to work with a dietician to develop a meal plan.
  • Try to exercise regularly if you’re able, though it’s not recommended that you start a new rigorous training program.
  • Drink plenty of fluids.
  • Limit your intake of caffeine, alcohol, and tobacco.
  • Talk about how you’re feeling with friends, family, or professionals.
  • Take pain relievers if you develop sores in your mouth.
  • Follow any other particular instructions you’re given by your treatment team.
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More than half of people with cancer receive radiation therapy. However, people with certain health considerations may not be eligible for radiation therapy. These considerations include:

What should I know about radiation therapy?

Radiation therapy plays an important role in cancer treatment, but also comes with its own risks. Before deciding if radiation therapy is right for you, you may want to ask your doctor question such as:

  • How many treatments will I need?
  • What other treatments will I need?
  • What side effects are most likely?
  • What are the chances of developing severe side effects?
  • Who can help me manage side effects?
  • What is my prognosis with or without radiation therapy?
  • Are there any clinical trials I may be eligible for?
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Radiation therapy damages the DNA of cancer cells to help shrink tumors or slow the progression of cancer. It can also damage healthy cells and lead to side effects.

Common side effects include hair loss, fatigue, mood changes, nausea, and vomiting. Some side effects may not appear for months or years after treatment.

It’s important to alert your doctor or other health professionals about any side effects you’re having. They can help you avoid severe complications and adjust your treatment if necessary.