Radiation therapy

This page was reviewed under our medical and editorial policy by

Kevin King, MD, Radiation Oncologist, City of Hope | Downtown Chicago

This page was updated on December 22, 2023.

Radiation therapy is a type of cancer treatment that may be used alone or in combination with other treatment options.

What is radiation therapy?

Radiation therapy (also called radiotherapy) uses targeted energy, including X-rays and radioactive substances, to destroy cancer cells, shrink tumors and/or alleviate certain cancer-related symptoms. Doctors use high-energy X-rays and other forms of radiation therapy to damage the DNA in cancer cells, killing them or depriving them of their ability to grow or divide.

It may be used:

  • As a primary treatment to destroy cancer cells
  • In combination with other treatments to stop the growth of cancer cells
  • Before another treatment to shrink a tumor
  • After another treatment to stop the growth of any remaining cancer cells
  • During theranostics (cancer care that combine diagnostics and treatment)
  • To relieve symptoms of advanced cancer

Radiation therapy does not kill cancer cells immediately. Over several days and weeks, and during the course of treatment, the DNA in cancer cells may become damaged enough that they die or are no longer able to reproduce.

Radiation therapy is one of the most common types of cancer treatments. Approximately 60 percent of all patients receive radiation therapy as part of their cancer care plan. Radiation therapy may be used to treat both benign (non-cancerous) and malignant (cancerous) tumors. 

At City of Hope®, our radiation oncologists are experienced in using advanced technologies to deliver targeted radiation therapy while also proactively managing side effects. From treatment planning to follow-up care, our comprehensive cancer centers provide personalized patient care and state-of-the-art radiation oncology services to help patients fight cancer and manage its symptoms.

Types of radiation

Some radiation therapy delivery methods include:

Managing radiation side effects

Typical radiation therapy can be damaging to the body and cause unpleasant side effects, such as skin changes, fatigue, nausea and other issues, depending on the part of the patient's body being treated. During treatment, radiation therapists and clinicians from a variety of supportive care services will work with the patient to reduce radiation therapy side effects and improve his or her quality of life.

Some parts of the body may be more sensitive to radiation than others. And different body parts have different dosage limits. If a part of the body has been treated with radiation therapy before, it may no longer be a treatment option in that area. Talk to the care team if radiation therapy has to be used to discuss dosage limits to the area being treated.  

Individualized treatment approach

Radiation therapy is an important part of treatment for many cancer patients. Since each cancer type requires a different approach, each patient's treatment options depend on his or her unique needs and treatment goals.

Radiation oncologists use advanced imaging techniques before and during radiation therapy so the care team can closely track the tumor. They use highly targeted radiation technologies to deliver high radiation doses to tumors, with techniques designed to have less impact on healthy tissues and organs.

Depending on each patient's individual needs, he or she may receive radiation therapy alone or in combination with other treatment modalities such as surgery, chemotherapy, hormone therapy and/or immunotherapy. Throughout treatment, the radiation oncologist monitors the progress of the patient's radiation therapy regimen and modifies the treatment plan as needed.

Preparation for radiation therapy

Each patient’s experience with radiation therapy differs depending on the type of technology used, the type of cancer being treated and other factors. Before a course of treatment begins, the care team explains the type of radiation equipment to be used and discusses the treatment schedule and length of treatment. The patient also undergoes an examination.

The care team may place marks on the patient's skin or fiducial markers near the tumor to allow quick identification of the target treatment area. The patient may also be fitted with devices designed to immobilize parts of the body during treatment. These steps are intended to help doctors ensure that the patient is in the same position during each treatment. 

In most cases, radiation therapy is delivered in an outpatient setting over a period of days or weeks. Some patients undergo a single treatment while others are scheduled over several weeks.

Does radiation therapy hurt?

Radiation therapy is typically a relatively quick and painless treatment, and many patients are able to resume their normal activities before and after treatment. Over time, patients may experience common side effects, such as fatigue or irritation to the skin.

Cancer treatments are often stressful, upset the patient's normal routines and take a physical toll. It’s important to take steps, such as the following, to help stay physically strong during the course of treatment:

  • Get plenty of rest
  • Stay hydrated
  • Eat well
  • Stay vigilant for side effects or physical changes
  • Communicate any questions or concerns with the care team

Supportive care providers will work with patients to help address and, when possible, prevent side effects so they are better able to maintain their strength, stamina and quality of life, during and after cancer care.