You may have heard about radiation therapy for cancer and are wondering when it’s used. Here, you’ll learn the basics about radiation therapy (sometimes called radiotherapy), how it works and why it might be used to treat cancer. Use the following links to jump ahead for specific information about radiation therapy.

It’s always great to learn as much as you can about possible treatments, but it’s important to remember that the most effective treatment will depend on the type and stage of cancer, and a person’s health and care preferences. Talk to an oncologist to learn the best treatment for you or your loved one. Make sure to follow up with your oncologist about any questions you have.

What is radiation therapy for cancer? A cancer treatment that uses radiation to kill cancer cells.

Radiation therapy is a type of cancer treatment that uses high doses of radiation to kill cancer cells, or slow their growth and shrink tumors. It’s typically used as a targeted treatment, meaning that the radiation is applied to a specific tumor. It can also be used as a systemic treatment, using medicines that travel through the blood to treat cancer cells throughout the body, though this isn’t as common.

There are different types of radiation therapy, but it’s most often delivered using beams from a machine (more on that below).

Radiation works by damaging the DNA of cancer cells

Radiation therapy uses large amounts of radiation to damage the genetic material of cancer cells. This damage to cancer cells can cause them to stop growing, dividing and die – which helps keep cancer from spreading. And when the cells die, the body breaks them down into smaller components, like sugars and nucleic acid, that the body can safely reuse.

Chemotherapy vs. radiation therapy: How they’re different

Both are cancer treatments, but chemo uses strong drugs that target and kill fast-growing cells, such as cancer cells. Chemotherapy medicines are usually given by mouth, through a vein or with a shot, and then spread to the rest of your body through your blood. It’s very rarely used as a targeted treatment.

Why radiation therapy may be included as part of a treatment plan

Radiation therapy is a common treatment and can be used for most types of cancer. About half of cancer treatment plans include some sort of radiation therapy. For certain cancers, radiation therapy is the only treatment, but it’s usually used as part of a combination treatment plan. Ways that radiation is used with other treatments include:

  • Before other treatments – Radiation therapy can shrink the size of a tumor so it’s easier to remove and less likely to return.
  • After other treatments – Radiation therapy may be used to kill cancer cells that remain after other treatments.
  • To help with cancer symptoms – Radiation therapy can shrink tumors to reduce pain and other problems caused by the tumor (for example, problems with breathing or bladder and bowel control).

Types of radiation therapy for cancer

Radiation therapy takes time to work. It can take days or weeks of treatments before the body starts to destroy cancer cells. The number of treatments a person needs depends on the cancer, the treatment plan and the type of radiation therapy. The two main types are external beam radiation therapy and internal radiation therapy. An oncologist may recommend a certain type of radiation therapy for several reasons, including:

  • The cancer – The size and type of cancer.
  • The location – How close the cancer is to healthy tissues that are sensitive to radiation and if there’s cancer in more than one location.
  • The treatment plan – If the treatment plan will include other types of cancer treatment.
  • A person’s age and overall health – If the person has other medical conditions or health factors that may affect how treatment works.

External beam radiation therapy (EBRT)

External beam radiation therapy is the most common type of radiation therapy for cancer. It uses a machine that doesn’t touch the body to send intense beams of energy to a very specific area of the body.

This type of radiation doesn’t make a person radioactive. After a treatment, it’s safe to be around others, even pregnant people and children.

Types of external radiation therapy

  • Three-dimensional conformal radiation therapy (3D-CRT) – This treatment sends radiation beams from multiple directions to target the specific shape of the tumor.
  • Intensity-modulated radiation therapy (IMRT) – This treatment is similar to 3D-CRT but uses beams of radiation of varying strengths. With IMRT, higher doses of radiation can be used without increased damage to the surrounding tissue.
  • Stereotactic body radiotherapy (SBRT) – This treatment delivers high doses of radiation to the tumor while minimizing damage to other tissues. The radiation is more intense than that offered by IMRT and is typically used for smaller tumors.
  • Stereotactic radiosurgery (SRS) – This is not actually surgery, but a very precise way to treat brain cancer that uses brain scans for targeting. With this type of therapy, the full radiation dose may be given in one session.
  • Image-guided radiation therapy (IGRT) – This means that imaging tests (such as MRI or a CT) are given before starting any kind of external beam radiation therapy.

Brachytherapy

With brachytherapy, the source of radiation is an implant that’s put inside the body. The name comes from the Greek word “brachy” which means short. With brachytherapy, there’s a short distance between the radiation source and the tumor. During this treatment, a sealed radiation source is carefully placed into the tumor or nearby tissues. The radiation source may be kept in place for a few minutes and removed. Or there are also permanent implants that are left in the body forever, even after the radiation has been used up – these are about the size of a grain of rice and generally don’t cause any discomfort.

If a person has permanent brachytherapy, the treatment area will give off low doses of radiation for a while. The risk to others is usually low and a person’s oncologist will provide instructions on how to keep everyone safe.

Systemic radiation therapy

Systemic radiation therapy is sometimes used when cancer has spread or if there is cancer in multiple locations. This treatment uses liquid radioactive drugs (called radiopharmaceuticals or radionuclides) that travel through your blood to reach cancer cells throughout your body. These medications can be given by mouth, through a vein or with a shot. After systemic radiation, bodily fluids (urine, sweat and saliva) can give off radiation for a few days.

After receiving systemic radiation therapy, a person may need to change or limit interactions with others for a while. The oncologist will discuss what changes need to be made to keep everyone safe – whether staying at the hospital or going home after treatment.

Potential side effects of radiation therapy

Radiation therapy can affect nearby healthy cells, which may cause some side effects. To limit side effects, oncologists carefully plan treatments so that radiation therapy is used on the smallest possible area.

The side effects depend on the type of radiation therapy, but one of the most common side effects is fatigue. Other side effects depend on the area of the body being treated and include skin problems, hair loss, appetite changes, nausea, malnutrition, coughing and shortness of breath.

Healthy cells are much better at repairing themselves than cancer cells. Because of this, side effects often go away after treatment is complete – but it may take a few months. It’s also possible to have long-term side effects.

An oncologist will let you know what to expect. If side effects occur, your care team will put together a plan to help manage them – for example, they may adjust the dose or suggest using cannabis for cancer.

There are lifetime limits for radiation therapy

Too much radiation isn’t safe, and there’s a limit to how much radiation an area of the body can receive. This may impact whether radiation therapy is an option. A person may not be able to get radiation therapy in an area of the body for a second time. But if radiation therapy was used as a treatment in one area, it’s possible that it could be used in another area of the body, as long as they’re not too close together.

Cancers treated by radiation therapy

The following are some ways that radiation therapy is used to treat cancer:

  • Bone cancer – External radiation and systemic radiation are used to treat bone cancer. Radiation therapy works better for Ewing sarcoma than other types of bone cancer, and it’s often used with chemotherapy.
  • Blood cancer – Radiation therapy (usually external radiation) is sometimes used as part of a combination treatment plan for leukemia and lymphoma. It’s rarely used on its own.
  • Brain and spinal cancer – Radiation therapy is often used as the main treatment for brain tumors, especially ones that are in hard-to-reach places. Depending on the tumor, external radiation (such as SRS) or brachytherapy may be recommended.
  • Breast cancer – Radiation therapy is used during nearly all stages of breast cancer treatment. It’s often used after other treatments to ease symptoms and to keep cancer from coming back. Depending on the situation, external radiation or brachytherapy may be recommended.
  • Colon and rectal cancer – External bean radiation therapy is often used to shrink tumors before colon or rectal cancer surgery. If surgery isn’t an option, radiation therapy can help reduce pain and other symptoms.
  • Eye cancer – Radiation therapy (usually brachytherapy) is often the main treatment for eye melanoma. It may save some vision in the affected eye.
  • Gynecologic cancer – Radiation therapy is often part of the treatment plan for gynecologic cancers such as cervical cancer, endometrial cancer and vaginal cancer. An oncologist may recommend external radiation, brachytherapy or both.
  • Lung cancer – When used for lung cancer, radiation therapy can be the main treatment or to make other treatments work better. Either external radiation or brachytherapy may be recommended.
  • Prostate cancer – Radiation therapy, either external radiation or brachytherapy, is often used as part of a combination treatment plan for prostate cancer. Brachytherapy is sometimes used on its own if cancer is in the early stages.
  • Skin cancer – Radiation therapy is sometimes the main treatment for skin cancer if the tumor is large or in a location that would make it difficult to remove with surgery. Radiation therapy is also commonly used after other skin cancer treatments. Depending on the situation, external radiation or brachytherapy may be used.
  • Thyroid cancer – Systemic radiation (radioactive iodine therapy) is a common treatment for certain types of thyroid cancer. External radiation therapy is also used in some cases.

 We’re ready to answer your questions about radiation for cancer

Talking to an oncologist is the best way to understand if radiation therapy makes sense as part of a treatment plan for you or your loved one. The team at HealthPartners is committed to providing personalized cancer care and ensuring that you feel confident about the treatment you receive. We’ll help you understand the benefits and drawbacks of different treatments, and what to expect. If you’re interested in being involved in clinical trials for cancer, we can discuss that too.

Throughout treatment, you’ll have a compassionate team of experts that includes oncologists, genetic counselors, surgeons, nurses, clinical trial researchers and many others. Whether you’ve received a cancer diagnosis or are supporting a loved one with cancer, we’ll be there for you every step of the way.