What is radiation therapy?

By | 4 May 2021

Radiation therapy, also known as radiation, is a type of cancer treatment that uses intense energy beams to kill cancer cells. X-rays are mostly used in that therapy, but protons or other types of energy may also be preferred.

The term “radiation therapy” often refers to external beam that therapy. During this type of radiation, high-energy rays come from a machine that targets rays outside of your body at a precise point on your body. During a different radiation therapy called brachytherapy (brak-e-THER-uh-pee), the radiation is placed inside your body.

That therapy damages cells by destroying the genetic material that controls how cells grow and divide. While both healthy and cancerous cells are damaged by the therapy, the goal of radiation therapy is to destroy as few healthy cells as possible. Normal cells can repair most of the damage caused by radiation.

Why is radiation therapy done?

More than half of all people with cancer receive therapy as part of their cancer treatment. Doctors use radiation therapy to treat almost any type of cancer. The therapy may also be useful in the treatment of some noncancerous (benign) tumors.

How is radiation therapy used in people with cancer?

Your doctor may recommend radiation therapy as an option at different times during your cancer treatment and for different reasons, including:

  • As the sole (primary) treatment for cancer
  • Before surgery, to shrink a cancerous tumor (neoadjuvant therapy)
  • After surgery, to stop the growth of remaining cancer cells (adjuvant therapy)
  • In combination with other treatments, such as chemotherapy, to destroy cancer cells
  • To relieve symptoms caused by cancer in advanced cancer

The therapy can also help treat symptoms when cancer spreads. At this point, it is part of palliative care aimed at relieving a person’s symptoms and improving their quality of life. It can also extend a person’s life in some cases.

Palliative radiation therapy usually involves lower doses and fewer treatment sessions than curative therapy. For example, in some people with bone cancer, palliative radiation therapy can help prevent the development of painful tumors.

Side effects of the therapy depend on which part of your body is being exposed to radiation and how much radiation is used. Some patients experience no side effects or may experience several. Most side effects are temporary, can be controlled, and usually disappear over time after treatment ends.

Common side effects on part of the body being treated:

  • Hair loss at the treatment site (sometimes permanent), skin irritation at the treatment site, fatigue
  • Dry mouth, thickened saliva, difficulty swallowing, sore throat, changes in the taste of food, nausea, mouth sores, tooth decay
  • Difficulty swallowing, cough, shortness of breath
  • Nausea, vomiting, diarrhea
  • Diarrhea, bladder irritation, frequent urination, sexual dysfunction

Some side effects may occur later. For example, in rare cases, new cancer (second primary cancer) different from first cancer treated with radiation may develop years later. You can get information from your doctor about possible short-term and long-term side effects that may occur after treatment.

Types of radiation therapy
There are two types of radiation therapy. These:

This is the most common type. It contains an external machine that emits a beam of radiation that targets the treatment area. Different forms are available depending on the need. For example, high-energy rays can target cancer deeper in the body.

There are different types of internal therapy. Both involve implanting or introducing radioactive material into the body.

Brachytherapy involves placing a radioactive implant in or near cancerous tissue. The implant can be temporary or permanent. Another type of internal radiation therapy involves receiving an injection of radioactive fluid. The aim is to limit the exposure of healthy tissue around cancer to radiation. Doctors may recommend this treatment for prostate or ovarian cancer, for example.

Your doctor may recommend both main types of therapy based on the type of cancer or the condition of the disease. The decision as to which treatment to take will depend on:

  • Cancer type
  • The size of the tumor
  • The location of the tumor, including nearby tissue types
  • The person’s age and general health

How do you prepare?

Before starting external beam radiation therapy, your healthcare team guides you through the planning process to ensure that the radiation reaches the needed sensitive point in your body. Planning typically includes:

Radiation simulation: During the simulation, your radiation therapy team works with you to find a comfortable position for you. It is imperative to lie down during treatment. Therefore, finding a comfortable position is vital. To do this, you lie down on a special table with the one used during the therapy. Cushions and restraints are used to position you correctly and help keep you still. Your radiation therapy team will mark the area where your body will be exposed to radiation. Depending on your situation, you can make temporary markings with a marker or use small temporary tattoos.

Scan planning: Your radiation therapy team will provide you with computed tomography (CT) scans to determine the area of ​​your body to be treated. After the planning process, your radiation therapy team decides what type of radiation and in what doses you will receive, depending on your cancer type and stage, your overall health, and the goals of your treatment.

The precise dose and focus of the radiation beams used in your treatment have been carefully planned to maximize radiation to your cancer cells and minimize damage to surrounding healthy tissue.

What are the expectations from radiation therapy?

External beam radiation therapy is usually performed using a linear accelerator, a machine that directs high-energy radiation beams into your body.

As you lie on a table, the linear accelerator moves around you to deliver radiation from several angles. The linear accelerator can be adjusted to your specific situation to give the exact radiation dose your doctor has detected.

You will usually receive outpatient external beam radiation five days a week within a certain time frame. In most cases, treatments are usually spread over several weeks to allow healthy cells to heal between radiation therapy sessions.

Each treatment session is expected to take approximately 10 to 30 minutes. In some cases, a single treatment may be used to relieve pain or other symptoms associated with more advanced cancers.

During a treatment session, you lie down in the position determined for the radiation simulation session. Molded systems are used to hold you in place.

The linear accelerator machine can rotate around your body to reach the target from different directions. The machine buzzes.

During the treatment, which only takes a few minutes, you will stop and breathe normally. For some patients with lung or breast cancer, you may be asked to hold your breath while the machine is performing the treatment.

Your radiation therapy team is in a room with video and audio connections so you can talk to each other. You should speak up if you are uncomfortable, but you will not feel any pain during your radiation therapy session.


If you are receiving radiation for a tumor, your doctor may order periodic screenings after treatment to see how your cancer is responding to the therapy. In some cases, your cancer may respond immediately to treatment. In other cases, it may take weeks or months for cancer to respond. Radiation therapy may not help some people.

Discuss any concerns with the doctor and ask as many questions as possible. Knowing what you can expect from treatment can help with treatment. Do not neglect to have regular checks for your health.


The page content is for informational purposes only. Items containing information about therapeutic health services are not included in the content of the page. Consult your physician for diagnosis and treatment.