Radiation Therapy for Cancer

Medically Reviewed by Jennifer Robinson, MD on August 15, 2022
4 min read

If you've been diagnosed with cancer, your doctor may suggest you get radiation therapy. It's a common treatment that shrinks tumors and kills cancer cells -- and might be the only one you need to tackle your disease.

Cells in your body are always dividing and making new copies. When you have cancer, though, some cells start to divide way too fast.

That's where radiation therapy can help. It uses high-energy particles to make tiny breaks in the DNA of cancer cells to destroy or damage them, so they can no longer make new copies.

The aim is to treat your cancer by slowing or stopping tumor growth. Your doctor may sometimes suggest you get radiation therapy to shrink a tumor before you get surgery. Or they may recommend it after surgery to keep a tumor from coming back.

If cancer cells have spread to other parts of your body, radiation therapy can kill them before they grow into new tumors.

If you have a cancer that can't be cured, your doctor may still suggest you use "palliative" radiation therapy. The goal is to shrink tumors and ease symptoms of your disease.

The kind of radiation therapy you get depends on things like:

  • Type of cancer you have
  • How big your tumors are
  • Where your tumors are
  • How close your tumors are to other tissues
  • Your general health
  • Other treatments you're getting

The two main types of radiation therapy for cancer are:

External beam radiation therapy. A large machine aims radiation beams from outside your body to a cancer tumor from many angles. It can treat a variety of cancers.

The machine can be quite noisy, but it won't touch you. It sends radiation to the specific area where there's cancer. It uses computer programs to analyze imaging scans and target treatments to the shape of your tumor.

A visit usually lasts 30 minutes to an hour, most of which is spent getting you in the correct position. The treatment itself usually takes 5 minutes or less.

Most people get a dose 5 days a week. Your schedule may vary. It depends on the type of beam used and other things, including the type, size, and location of the cancer.

External beam radiation therapy won't make you radioactive, so you can safely spend time around other people.

Internal radiation therapy. You'll get radiation placed inside you in either solid or liquid form. You might swallow or get an IV injection of liquid radioactive iodine, which will travel throughout your body to seek and kill cancer cells. This is called systemic therapy. Doctors use it most often to treat thyroid cancer.

In another option, called brachytherapy, a technician places a solid form of radiation -- like a capsule or other type of implant -- into your body. They put it inside you using a small tube called a catheter or a device known as an applicator.

Brachytherapy usually treats head, neck, breast, cervix, endometrial, prostate, and eye cancers.

If your doctor uses a low dose of radiation in brachytherapy, they'll remove the implant after several days. If they use a higher dose, they usually take it out after 10 to 20 minutes, and you'll get two doses a day for around 2 to 5 weeks.

Depending on the type and location of your cancer and the other treatments you've had, your doctor may also place an implant in your body permanently and the radiation will weaken with time.

After you get internal radiation therapy, your body or your body fluids may give off radiation for a while, so you'll likely stay in a hospital and will need to avoid or limit visits with loved ones at first.

Whatever type of radiation therapy you get, you'll have regular follow-up appointments to check that it worked. Your doctor will examine you and discuss side effects and symptoms. They may also order lab and imaging tests, including blood tests, X-rays, or CT, MRI, or PET scans, to check for signs of cancer.

Radiation therapy may slightly raise your risk of other types of cancers. The risk is small enough that it's usually outweighed by the benefits, but your doctor will help you decide what treatment is best for you.

Let your doctor know if you're pregnant or planning to become pregnant. Radiation therapy can harm an unborn baby. Not much is known about how it affects sperm, so doctors usually suggest men avoid getting their partners pregnant during and a few weeks after treatment.

Because radiation therapy also affects your healthy cells, it can cause side effects. These might appear during treatment and vanish weeks later, or they might last for years. Some may even show up for the first time months or years later.

Depending on the part of your body that's getting treated, side effects may include fatigue, temporary hair loss, sexual and fertility problems, blurry vision, and skin changes.

Some other problems you could have are:

Talk to your doctor if you have any of these side effects. There are steps you can take, including medicine, that can help ease your symptoms.