Does Radiation Therapy for Cancer Work?

Radiation therapy (also called radiotherapy) uses high-powered waves to break down the genetic material inside cancer cells and kill them. This is done to either shrink or completely destroy cancer masses (tumors) in organs or tissues.

While radiation therapy can be an effective treatment for cancer, it can also cause some severe side effects. In this article, we'll discuss what radiation therapy is, why it's used, and what to expect during treatment.

Radiation therapy

skynesher / Getty Images


Radiation therapy describes treatments that use high-powered waves of energy to destroy the genetic materials (DNA) in cancer cells. Ionizing radiation, the same kind of radiation used in X-rays and gamma rays, is usually used in radiation therapy because it is more powerful than the nonionizing waves that are used in microwave and radio signals. In some cases, lower levels of radiation are used, depending on the type of cancer.


The types of radiation waves used to treat cancer are usually divided into several subgroups, and each group is used to treat particular types of cancer like:

  • Electron beams: These are low-energy waves used to treat skin cancers and tumors that are close to the surface of the skin.
  • Proton beams: These use a delayed release energy that spares collateral damage to healthy tissues.
  • Photon beams: These are the strongest types of radiation beams.
  • Neutron beams: These are often used for cancers of the head, neck, and prostate, and for inoperable tumors.
  • Carbon ion: This method uses the heaviest type of radiation particles, usually to treat cancers that are resistant to other types of radiation therapy.
  • Alpha and beta particles: These are weaker particles that are usually used in radiation studies but can sometimes be used to treat cancer.


When the time comes to have your first radiation therapy session, here's what to expect:

  • On the day of treatment, you may want to eat lightly before your visit. If you become nauseated after your session, you may want to avoid eating for a few hours before your next treatment.
  • Wear loose, comfortable clothing. You may even be asked to change into a hospital gown.
  • You will be placed on a treatment table with a hard surface. A technician will position you to ensure the best access to the treatment area.
  • Boards or immobilization devices may be used to make sure you don't move during treatment. While you can't move during radiation therapy, it's all right to breathe normally.
  • Even though you will be alone in the treatment room, you will be observed at all times by medical staff. Let them know immediately if you have any problems or need to move.
  • Every radiation therapy appointment is different, but generally treatment sessions last 10–30 minutes, with doses of radiation given for one to two minutes at a time. Most people will receive radiation treatment five days a week for two weeks to two months.
  • Your radiation team will meet with you weekly to discuss your therapy and any concerns or side effects you're having.

External Beam Radiation Therapy

This uses a machine called a linear accelerator to send radiation waves—typically photon beams—through your body to the location of your cancer. This therapy is typically done in a series of outpatient visits to a treatment center, usually over a course of several weeks. It can involve:

  • Three-dimensional conformal radiation therapy: Three-dimensional images are used to create a mold and target the specific location of the cancer to reduce damage to surrounding tissues.
  • Intensity modulated radiation therapy: Three-dimensional images are used to target therapy to a specific cancer location, but several high-powered beams are used to deliver radiation and the strength of each beam can be adjusted during the session.
  • Proton beam therapy: Proton beams require a special machine to deliver, and these machines are rare and costly, so this type of therapy is not available in many facilities.
  • Image-guided radiation therapy: This technique uses radiation machines outfitted with imaging scanners that can help deliver beams to more precise locations, reducing damage to surrounding tissues.
  • Stereotactic radiation therapy: This type of therapy uses imaging tools to deliver large doses of radiation to small tumors.

Internal Radiation Therapy (Brachytherapy)

Internal radiation therapy includes:

  • Permanent implanted: With permanent implanted radiation, tiny steel particles called seeds that are about the size of rice grains and contain radiation are implanted into your body. Over time, the radiation loses its energy, but the seeds will remain in your body.
  • Temporary internal: This type of radiation is placed into the body by a needle or catheter, a thin, flexible tube. It is inserted at the treatment site and can stay in the body for hours to days. You may need to be isolated as the radiation leaves your body to protect those around you from exposure.

Electromagnetic-guided Radiation Therapy

This type of therapy uses small electromagnetic implants to help direct external beam radiation to specific treatment areas. It is sometimes referred to as four-dimensional radiation therapy. Despite its goal to reduce side effects to healthy tissues, there isn't much data to show that this therapy is superior to other types of radiation therapy.

Systemic Radiation Therapy

Systemic therapy indicates that radiation is being used throughout the body. An oral medication, a capsule containing radioactive material, or an injection is given over a period of time. It can affect the whole body and exit your system through blood, sweat, or urine.

Those around you should take care around these fluids to avoid exposure. An example of this type of radiation is radioactive iodine therapy for thyroid cancer.

Intraoperative Therapy

Intraoperative therapy is radiation that is delivered during a surgical procedure using either external beams or implanted radiation. This is used to treat particularly deep cancers that are difficult to reach without damaging large amounts of tissue. With this technique, noncancerous organs and tissues can be moved aside during treatment to allow maximum benefit with fewer side effects.


This uses antibodies located on certain cells to target its effects and reduce damage to other healthy cells. An example of this type of therapy is Zevalin (ibritumomab), which is used to treat lymphoma, blood cancers that affect a type of blood cells called lymphocytes.

Radiosensitizers and Radioprotectors

These are new strategies that aim to make radiation more effective while reducing the harmful effects. Radiosensitizers are compounds that can make cancer cells more sensitive to the effects of radiation, while radioprotectors can help protect health tissues. Research is still underway to determine how effective these treatment methods are.

Who Does It

Radiation therapy is performed primarily in outpatient centers or ambulatory clinics by a specialized team of clinicians that can include the following:

  • A radiation oncologist specializes in radiation treatment.
  • A radiation physicist focuses on the radiation equipment and dosing.
  • A dosimetrist works with the oncologist to develop a treatment plan.
  • A radiation therapist operates the equipment and gets you into the correct positions.
  • A radiation therapy nurse helps you understand your therapy and manage side effects.


Radiation therapy is generally used to treat cancer by targeting the DNA of cells that are actively dividing. Since cancer cells divide so rapidly, many of these cells are susceptible to damage from radiation at any given time. Healthy cells can be impacted too, though, so radiation therapy uses a balancing act of using radiation to destroy cancer cells while preserving healthy cells.

Radiation therapy is typically used in the following ways during cancer treatment:

  • As a standalone therapy
  • Alongside chemotherapy
  • Before surgery to help reduce the size of a tumor
  • After surgery to destroy any remaining cancer cells
  • To shrink tumors to help control symptoms and improve comfort in terminal cancers

How to Prepare

You will have a number of preliminary appointments in which measurements and scans will be taken using a CT (computed tomography) scan. Your oncology team may mark measurements or specific sites on your skin with ink or even a small tattoo.

One of these preliminary appointments will be a simulation visit, in which you will run through a typical treatment session, the location and size of your cancer will be mapped, and other measurements will be taken. After that, your radiation oncology team will develop a plan, including what radiation type and dose should be used, to best suit your treatment goals.

Side Effects of Radiation Therapy

Radiation doesn't only work during individual treatment sessions. Cells that are impacted by radiation at the time of treatment can take days—or even months—to die off completely. In most cases, this cell death, as well as damage to surrounding tissues, is what causes the side effects from radiation therapy.

Fatigue, hair loss, and skin changes are common side effects of radiation therapy, but you can also have other side effects depending on the part of your body where treatment is targeted.

Long-Term Side Effects

While many of the side effects only appear while you are undergoing radiation therapy and a short time thereafter, there is also a chance that some effects won't develop for quite a while. Some side effects that can develop in the months and years after you complete radiation therapy include:

  • Bone loss
  • Memory or cognitive problems
  • Early menopause
  • Weight gain
  • Thyroid problems
  • Blurry vision
  • Sensitivity to light
  • Heart or lung damage


Radiation therapy isn't an instantaneous treatment. It takes days, weeks, or even months for radiation to continue its work of destroying cancer cells. It's also important to note that radiation therapy often isn't used alone. It's usually used along with other treatments like chemotherapy or surgery, so it's difficult to tell the impact of radiation therapy on its own.

Still, as an adjunctive treatment (one that assists the primary treatment), it appears to do good work. According to a 2017 review of trends in cancer therapies, roughly one-third of all five-year cancer survivors had received radiation therapy as a part of their cancer treatment.

People who survived breast and prostate cancers made up the bulk of that group, but survivors of head, neck, rectal, and lung cancers also fared well with radiation therapy as a part of their treatment plan.

Whether your cancer responds to radiation therapy or returns after your cancer has been successfully treated depends a lot on a number of factors like:

  • Cancer type
  • Cancer stage
  • Location
  • Age
  • Overall health
  • Other health conditions you have


Radiation therapy isn't painful, but it can be draining. Some people continue to work during their treatment, but getting enough rest is one of the best ways to care for yourself during radiotherapy.

No matter what kind of cancer treatment you receive, taking care of your health and having a strong support system are key. Below are some steps you can take to care for your body and mind and address the side effects of radiation therapy:

  • Be gentle with the skin over your treatment site.
  • Wash your skin gently and use mild soap, then pat dry.
  • Wear loose, soft clothing over your treatment area.
  • Protect your skin from the sun.
  • Do not use heating pads or ice over the treatment area.
  • Consider nutritional supplements to get adequate nutrition.
  • Eat several small meals each day instead of fewer large meals.
  • Avoid greasy, fried, or fatty foods and caffeine
  • Quit smoking.
  • Avoid alcohol.


Radiation therapy is used to treat cancer. It uses radiation of various strengths to kill cancer cells while preserving other healthy cells in your body. It may take a while for radiation therapy to work, and sometimes you may experience side effects not only during and shortly after your treatment but also a while after your treatment is complete.

How well you respond to radiation therapy depends on a number of factors, including your age, overall health, the type of cancer you have, and at what stage your cancer was diagnosed.

A Word From Verywell

There are many forms of radiation—delivered in a number of ways—that can help treat cancer. High-powered radiation beams destroy the genes inside cancer cells to kill them, but they can kill healthy cells in the process, too.

If radiation therapy is part of your treatment plan, be sure to talk to your doctor about the side effects of radiation and how to manage them. Getting plenty of rest, eating well, and having a strong support system will go a long way in helping you along your journey as you fight cancer.

Frequently Asked Questions 

Is radiation therapy used for all cancers?

Radiation may be used for a wide variety of cancers, but it works better for some than for others. Breast and prostate cancers respond particularly well to radiation treatment.

How long does a radiation therapy session last?

Sessions don't usually last more than a half hour, and much of this time is spent on positioning.

What’s the difference between radiation therapy and chemo?

Radiation therapy is performed with a beam of energy that destroys the genetic material inside cancer cells as they divide. Chemotherapy also targets cancer cells as they divide, but it is a medication that is usually given intravenously or orally.

What helps with radiation side effects?

Getting lots of rest, good nutrition, and gentle skin care can all help you deal with the side effects of radiation therapy. If you need additional help, your doctor may be able to prescribe you medications for side effects like nausea.

Are there alternative treatment options for cancer?

There are many treatments and combinations of treatments used for cancer. Radiation can be used alone or with other treatment strategies like chemotherapy and surgery. Alternative therapies and adjunctive treatments are always being researched and developed, but you should talk with your medical team about any new treatments you would like to try. They can also guide you if you are interested in participating in a clinical trial for new therapies.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American Cancer Society. The science behind radiation therapy.

  2. University of Iowa Hospitals & Clinics. Radiation therapy-what to expect.

  3. American Society of Clinical Oncology. Understanding radiation therapy.

  4. Ruba T, Tamilselvi R. Radiosensitizers and Radioprotectors for Effective Radiation Therapy– A Review. AJAST.

  5. American Cancer Society. How radiation therapy is used to treat cancer.

  6. National Institutes of Health. Radiation therapy to treat cancer.

  7. National Institutes of Health. Radiation therapy side effects.

  8. National Institutes of Health. Late side effects of cancer treatment.

  9. Bryant AK. Trends in radiation therapy among cancer survivors in the United States. CEBP. 2017 January 17. doi:10.1158/1055-9965.EPI-16-1023

By Rachael Zimlich, BSN, RN
Rachael is a freelance healthcare writer and critical care nurse based near Cleveland, Ohio.