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Radiation Therapy

Radiation Facts
  • Radiation therapy does not make patients radioactive.

Radiation therapy is a cancer treatment that uses focused beams of radiation to shrink or kill tumors. 

This page talks about external beam radiation therapy. To learn more about internal radiation therapy, please visit the Nuclear Medicine page.

On this page:
  • About Radiation Therapy
  • What you can do
  • Where to learn more


About Radiation Therapy

Radiation Therapy Image
Radiation therapy is a cancer treatment that uses focused beams of radiation to shrink or kill tumors.
Source: National Cancer Institute (NCI)

Radiation therapy uses ionizing radiation to shrink or kill tumors. Focused beams of radiation are produced by a machine outside the body and are aimed at tumor cells inside the body, damaging cells and destroying their ability to divide.

During radiation therapy radiation beams target tumors but can also damage healthy cells. Before starting therapy, doctors carefully plan where to aim the radiation beam to damage the tumor as much as possible, while doing as little damage to healthy cells as possible.

Radiation therapy does not make the patient receiving the treatment radioactive. Like shining a flashlight at your skin, your skin is illuminated where the beam hits your skin. When you turn the flashlight off, your skin returns to its normal shade and is no longer illuminated.

There are many different types of radiation therapy that can be used to treat tumors. Some examples of radiation therapy include:

  • Three-dimensional Conformal Radiation Therapy (3D-CRT): 3D-CRT is a type of radiation cancer treatment that uses special computers to get an accurate picture of the size, shape and location of the tumor. 3D-CRT can use single or multiple x-ray beams to target the tumor.
  • Proton therapy: Proton therapy uses a beam of protons to target tumors. Unlike x-rays, which deposit energy along their path, protons deposit the majority of their energy at the end of their path. Doctors use proton therapy to minimize damage to healthy tissue while still targeting the tumor.

Radiation therapy can cause acute side effects, such as hair loss or nausea, which can occur during treatment. Most acute effects disappear after treatment. Because radiation damages cells, it can also increase the risk of cancer. There is a small chance that the cancer treatment itself will produce another cancer years later. Radiation therapy patients are screened frequently for cancer after successful treatment of their primary tumor.

Doctors and scientists continue to research radiation therapy methods to increase accuracy, decrease damage to healthy tissue, and reduce side effects to the patient.

What You Can Do

  • Follow instructions given by their doctor or radiation therapist. Make sure to let the doctor and radiation therapist know if you are pregnant, might be pregnant, or are breastfeeding.

Where to Learn More

EPA is not a medical agency, and does not regulate radiation therapy.  For more information, please visit the links below.

The States

State radiation programs work with the U.S. Food and Drug Administration (FDA) to keep radiation therapy machines safe. Individual states regulate the use of x-ray equipment in medical, dental and veterinary work. States also register and inspect this equipment.

State Radiation Protection Programs
The Conference of Radiation Control Program Directors  (CRCPD)
This webpage provides links and contact information for each state's Radiation Control Program office.

The U.S. Department of Health and Human Services (HHS), the U.S. Food and Drug Administration (FDA)

States regulate the use of x-ray equipment. The FDA's Center for Devices and Radiological Health (CDRH) regulates the manufacturing of radiation-emitting electronic equipment.

About the Center for Devices and Radiological Health 
This webpage provides information on the program within the FDA that regulates the manufacturing of radiation-emitting devices.

U.S. Department of Commerce (DOC), National Institute of Standards and Technology (NIST)

NIST does not regulate medical equipment used in external beam radiation treatment. However, NIST makes x-ray machines safer for patients and workers by updating the technology and measurement standards used to design x-ray machines.

Radiation Physics Division 
This webpage links to more information on NIST's role in creating and maintaining standards for ionizing radiation in the United States.

The U.S. Department of Homeland Security (DHS), the U.S. National Institutes of Health (NIH), National Cancer Institute (NCI)

NCI is the federal government's principal agency for cancer research and training.

What to Know About External Beam Radiation Therapy
This document discusses what you should expect during radiation therapy treatment.

Radiation Therapy for Cancer
This webpage provides information on different types of radiation therapy, including external beam.

The American College of Radiology and Radiological Society of North America (ACR)

ACR and RSNA sponsor a public information website to educate the public about radiological procedures and the role of radiologists in healthcare, and to improve communications between physicians and their patients.

External Beam Therapy
The American College of Radiology and Radiological Society of North America
This webpage provides information about external beam therapy.

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Last updated on August 21, 2024
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