Radiation therapy is a cancer treatment that uses high-frequency waves to destroy cancer cells. Doctors determine the type of radiation and dose based on the type and location of the cancer as well as your general health and other factors.

Radiation therapy is a cancer treatment that uses high-energy waves to damage or destroy cancer cells.

The waves stop cancer cells from growing and making more cancer cells by affecting the DNA inside of them. However, it can sometimes damage noncancerous cells.

Radiation therapy targets an affected area with high-energy waves, often the location of a tumor or the place where a tumor was removed during surgery to destroy any remaining cancer cells.

This type of treatment is sometimes ideal because it allows doctors to only affect specific parts of your body, unlike other cancer treatments like chemotherapy that can affect cells in your entire body.

You see lower doses of radiation used in other parts of medicine like X-rays.

According to the American Cancer Society, more than half of people with cancer undergo radiation therapy. It can be your only treatment. Or, it can be given with other types of treatment, such as surgery and chemo.

There are two types of radiation therapy, and your doctor will consider many factors when deciding which is best for you, including:

  • cancer type
  • tumor size
  • location of cancer
  • the proximity of cancer to other tissues sensitive to radiation
  • your overall health and well-being
  • whether you’ll need other cancer treatment
  • age

External beam radiation therapy

With external beam radiation therapy, a large machine sends radiation waves to the site of cancer from outside the body.

You can’t see the rays, and the apparatus doesn’t touch you but moves around you. The movement allows it to send the radiation from many different directions.

Doctors use this type of radiation as a local treatment to target a specific part of your body. For example, when used for breast cancer, the radiation is targeted only at your chest instead of your whole body.

Internal radiation therapy

Internal radiation therapy is done in different ways. With brachytherapy, a doctor may implant a source of radiation into your body near the cancer site. The sources of radiation are often in the form of:

  • capsules
  • ribbons
  • seeds
  • balloons
  • wires
  • tubes
  • liquid

This process usually takes place inside an operating room in order to contain the radiation. Doctors and technicians typically use imaging tests to be sure the implant goes in the place it needs to.

You may be given general anesthesia to put you to sleep during the procedure. Or, you may receive local anesthesia to numb the area where you’re receiving the implant.

Depending on the strength of the radiation and the size and location of the implant, you may need to stay in the hospital for a few days for treatment. If your implant is smaller, you may be able to go home after treatment, but you’ll likely have specific guidelines and precautions to follow.

Radiation remains a local treatment that tackles a specific part of the body.

When receiving radiation in the liquid form, it’s administered via the mouth, IV line, or injection. Your bodily fluids may also give off radiation for some time after the test. For skin cancers, this type of radiation may be applied directly to the skin.

Radiation therapy is an essential tool for treating cancer and is often used with other therapies, such as chemotherapy or tumor removal surgery. The main goals of radiation therapy are to shrink tumors and kill cancer cells.

There are many reasons why doctors may choose to treat cancer with radiation. They use it to:

  • destroy all cancer cells
  • shrink the tumor
  • stop cancer from coming back
  • treat cancer symptoms

For example, one 2017 study discusses the effects of using radiation therapy to treat cancer that has spread to the bones. The overgrowth of cancer cells has put pressure on the nerve endings inside the bones. The cancer cells also cause the muscles to spasm. These can both lead to pain.

Radiation therapy may help relieve that pain by preventing the cancer cells from growing and reducing the amount of inflammation around the part of your body where the cancer is. It may not cure the cancer, but it may help halt its growth and increase your quality of life with less discomfort.

Every person reacts to radiation therapy differently. It’s best to consider that side effects are possible, though you may not experience all or any of them.

The location and type of cancer along with your general health may impact the severity and number of side effects. Any pre-existing conditions you had before receiving the diagnosis of cancer may also affect how you respond to treatment.

Some side effects can be seen at the time of treatment or just after. However, you may experience long-term side effects months or years after radiation. Consider discussing and planning for these side effects with your doctor in advance. They can help determine how to prevent or manage side effects when possible.

The most common side effects of radiation therapy can include:


When you experience fatigue, you may feel tired or have low energy. You can feel drained after radiation because some of your healthy cells may also be damaged along with the cancer cells. As you continue with more treatments, you may feel the tiredness grow.

The duration and severity of fatigue caused by radiation may be different depending on the type of treatment you receive. Typically, people receiving radiation therapy begin to feel fatigue around the third week of treatment. Fatigue often gets worse by the sixth week of treatment and can stay that way until the treatment is completed.

If you experience symptoms of fatigue, let your doctor know. They’ll want to monitor your condition and may suggest specific strategies to help.

Skin irritation

At the radiation site, your skin may start to change. The severity of that change can range from minor redness to developing sores.

Radiation dermatitis is a common reaction to treatment. You may experience some dryness and notice your skin flaking. However, it can also reach deeper layers of the skin, leading to blistering, pain, and bleeding.

To avoid radiation dermatitis, your doctor may suggest:

  • practicing proper skin hygiene using only warm water and mild soaps
  • avoiding any oil-based lotions or creams
  • wearing loose-fitting clothing
  • avoiding sun exposure and extreme temperatures
  • using steroid cream or gel-like hydrocortisone

It’s important to tell your doctor about any skin changes you’re experiencing to help ease discomfort and monitor the healing process. Sometimes, the problems go away on their own after you’ve completed treatment.

Certain parts of your body may also swell. For example, if you’re receiving treatments for breast cancer, the rays may cause the breasts to swell due to fluid buildup, also known as lymphedema.

How to protect your skin during radiation therapy

Skin changes are a side effect of receiving radiation, and you may need to take extra steps to protect it. Some ways to do this include:

  • Avoid wearing tight clothing or elastic over the area where you’re receiving treatment.
  • Use only paper tape on the affected area and avoid adhesive tapes.
  • Avoid scratching, scrubbing, and rubbing the area.
  • Talk with your doctor before using a heating pad or ice pack at the site.
  • Talk with your doctor about using sunscreen on the spot to further protect it from sunlight.
  • Use only mild soap and lukewarm water when cleaning the area while avoiding scrubbing.
  • Talk with your doctor before shaving the area.
  • Ask your doctor before applying any substance, such as creams, perfumes, or deodorants, on the spot.
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Hair loss

If you receive radiation therapy on places of your body that have hair, you may experience hair loss around the site. For example, if you receive radiation therapy on your head, you may lose some or all of your hair.

Your hair may grow back after treatment. However, you’ll want to take steps to protect your scalp and site from radiation. For example, if you wear a wig, make sure the lining doesn’t rub and irritate your scalp. It may also help to wear a hat or scarf when out in the sun to further protect the skin.

Low blood cell counts

As radiation kills cancer cells, it can also kill the healthy cells in your body responsible for helping you fight infections and stop bleeding. If your blood cell count becomes too low, your doctor may pause treatment until they come back up to a specific level.


As radiation therapy causes swelling and kills healthy cells, your body may react with pain. The doctor treating your cancer may suggest ways to manage your pain, including medication and other therapies.

Radioprotective drugs

Your doctor may prescribe medication, known as radioprotective drugs, that work to protect healthy tissue from radiation. These medicines only work for certain types of radiation and parts of the body but may be effective in reducing side effects.

Site-specific side effects

When you receive radiation to specific body parts, such as the brain or neck, you may experience other site-specific side effects. These side effects can include:


Head and neck





A team of doctors, including a radiation oncologist and a doctor who treats cancer with radiation, will determine your proper course of treatment. The team will also assess the dose and radiation frequency best suited for your cancer type and stage.

Preparation for radiation therapy involves a radiation simulation. It typically includes the steps seen below.

Radiation simulation

  • You’ll lie on the same type of table that will be used for your treatment.
  • Lying still at the proper angle is very important for treatment success, so your healthcare team may use cushions and restraints to position you for treatment.
  • You’ll then undergo CT scans or X-rays to determine the full extent of your cancer and where the radiation should be focused.
  • After determining the best location for radiation treatment, your treatment team will then mark the area with a very small tattoo. This tattoo is usually the size of a freckle. In certain cases, a permanent tattoo is not needed.
  • You’re now ready to begin radiation therapy.
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Radiation therapy can take place during treatment sessions several days a week for multiple weeks. Often, the person is given each weekend off from therapy, which helps restore normal cells. Sometimes, radiation therapy can be given less often or as a one-time dose. For some IV radiation treatments, it may be given once every few months.

The total number of treatments depends on the size and type of cancer.

At each session, you’ll lie on the treatment table, and your team will position you and apply the same types of cushions and restraints used during your initial radiation simulation. Protective coverings or shields may also be positioned on or around you to protect other body parts from unnecessary radiation.

Radiation therapy uses a linear accelerator machine, which directs radiation at the appropriate spot. The machine may move around the table in order to direct the radiation at the appropriate angles. The machine may also make a buzzing sound.

You should feel no pain during the session. You’ll also be able to communicate with your team via the room’s intercom, if necessary. Your doctors will be nearby in an adjacent room, monitoring the session.

Each session can take about 10 to 30 minutes.

During the weeks of treatment, your care team will closely monitor your treatment schedule and dosing, and your general health.

You’ll undergo several imaging scans and tests during radiation so your doctors can observe how well you’re responding to treatment. These scans and tests can also tell them if any changes need to be made to your treatment.

If you experience side effects from radiation — even if they’re expected — tell your healthcare provider at your next appointment. Sometimes, even small changes can make a big difference in limiting side effects. At the very least, you may receive advice or medication to help ease the discomfort.

Radiation therapy is a cancer treatment that uses high-frequency waves to destroy cancer cells.

It can be given:

  • externally from a machine, known as teletherapy
  • internally, through medications or injections, known as brachytherapy, directly to the affected area

Doctors determine the type of radiation and dose based on the type and location of the cancer as well as your general health and other factors. They determine the dosage to kill cancer cells while sparing normal cells.

Radiation therapy may cause side effects, including fatigue, skin irritation, hair loss, and others. However, some side effects may be managed or limited through other treatments or practices.