Radiation Therapy

Radiation therapy uses focused, high-energy photon beams to destroy cancer cells. More than half of cancer patients will undergo some type of radiation therapy. It may be used alone to cure the cancer or alongside other therapies, shrinking tumors before surgery or chemotherapy. It can also be used to destroy any cancer cells that might remain after other treatments.

How does radiation therapy work?

Almost all radiation is produced by a linear accelerator, or LINAC. It employs microwave energy to accelerate electrons to nearly the speed of light within a contained area. The electrons collide with a metal barrier, creating powerful X-rays called photons. The photons are shaped into beams and delivered to the patient through a gantry that moves 360 degrees around the treatment table.

A single dose of radiation is called a fraction. Most radiation treatments require several fractions. A typical radiation treatment plan has five fractions a week for one to six weeks.

Radiation therapy requires careful planning to ensure the tumor is targeted with the least amount of impact on surrounding tissues. CT scanners simulate treatments by testing various beam fields along with devices used to keep the patient from moving during treatment. Data from the simulators helps calculate the appropriate dose before treatment begins.

What diseases does radiation therapy treat?

Radiation therapy is mainly used to treat cancer by targeting and destroying cancer cells. It can be used for many types of cancer, including:

Brain tumors
Breast cancer
Colorectal cancer
Gynecologic cancers (such as cervical and endometrial cancer)
Head and neck cancers
Lung cancer
Lymphoma
Prostate cancer
Skin cancer

In some cases, radiation therapy is also used to shrink noncancerous (benign) tumors or relieve symptoms like pain.

Who gets radiation therapy?

You may receive radiation therapy if:

Your cancer is localized (in one area) and can be treated with targeted radiation.
You need radiation before surgery (to shrink a tumor) or after surgery (to kill remaining cancer cells).
You’re undergoing chemotherapy along with radiation (chemoradiation) for a stronger treatment.
Your cancer is advanced or spreading, and radiation may be needed to destroy any remaining cancer after treatments like chemotherapy, targeted therapy, or immunotherapy, or to help relieve symptoms (palliative care).

Your care team will decide if radiation therapy is right for you based on the type and stage of your cancer, your health and the treatments you've already received.

What happens during a radiation therapy procedure?

There are several steps to receiving radiation therapy:

Planning (Simulation): Your care team will take scans (CT, MRI) to map out the exact area to be treated.
Treatment sessions: You’ll lie still while a machine targets the cancer with radiation. Each session lasts 10-20 minutes and is usually given daily for several weeks.
Follow-up care: Your doctor will monitor your progress and manage any side effects.

Radiation therapy side effects

Radiation affects cancer cells but can also impact healthy tissues, leading to side effects. These depend on the area treated and may include:

Short-term side effects:
- Fatigue
- Skin irritation or redness (like a sunburn)
- Nausea or vomiting (if treating the abdomen)
- Hair loss (only in the treated area)
- Trouble swallowing (if treating the throat or chest)

Long-term side effects (can appear months or years later):
- Scarring or stiffness in the treated area
- Changes in skin texture or sensitivity
- Increased risk of secondary cancers (rare but possible)

Your care team will discuss ways to manage side effects and support your recovery.

Radiation Therapy: An introduction

Resources

Radiation Treatment Center

Our tools and expertise allow us to offer patients the most effective and advanced radiation treatments available.
Proton Therapy Center

The Proton Therapy Center uses a beam of protons to deliver radiation directly to the tumor.

Types of Radiation Therapy

Brachytherapy

Also called internal radiation, brachytherapy involves radioactive material that is implanted in or on the body. Dozens of tiny "seeds" containing radioactive iodine are placed at the tumor site with a special needle or catheter. In permanent brachytherapy, the seeds are left inside the body to release radiation over time. For temporary brachytherapy, the seeds are inserted for several minutes or hours and removed afterward, usually in an outpatient procedure.

3D conformal radiation therapy

This technique uses three-dimensional scans to determine the exact shape and size of the tumor. The radiation beams are shaped by tiny metal leaves that are arranged to fit the tumor dimensions (multi-leaf collimator), minimizing the side effects to healthy tissue.

Image guided radiation therapy (IGRT)

Image guidance is available on all of our radiation machines and includes X-rays, standard strength CT imaging built into radiation machines, and fully functional CT imaging scanners built into a treatment suite alongside the radiation machine. These imaging systems will track your tumor or implanted markers called fiducials during the course of radiation.

Intensity modulated radiation therapy (IMRT)

IMRT focuses multiple radiation beams of different intensities directly on the tumor for the highest possible dose. Radiation oncologists use special planning software to make sure the patient is properly positioned for the most accurate treatment.

Intraoperative radiation therapy (IORT)

IORT is used to treat an exposed tumor during cancer surgery. IORT is performed with a treatment unit that delivers a high dose of radiation to a surgically exposed treatment area. Surrounding healthy organs and tissues protected by lead shields or moved out of the radiation field.

MRI linear accelerator

This form of radiation is delivered within a fully operational MRI imaging machine. During the radiation administration, the MRI is constantly obtaining images, thus allowing for real-time control of the radiation beam during treatment. This type of machine is also capable of fine-tuning the radiation treatment plan between each treatment, thus, providing the ability to adapt the radiation delivery as needed on a daily basis.

Proton therapy

Proton therapy uses energy from protons instead of photons. Protons deliver their maximum amount of energy to the tumor with a minimal exit dose, resulting in fewer side effects than standard radiation therapy. MD Anderson’s Proton Therapy Center treats several types of cancer.

Stereotactic radiosurgery (SRS)

Stereotactic radiosurgery is not actually surgery. Instead, it uses dozens of tiny radiation beams to treat tumors in the head with a single radiation dose. MD Anderson uses the Gamma Knife^® SRS system.

Stereotactic body radiation therapy (SBRT)

SBRT delivers ablative doses to destroy cancer cells. It links CT scans of the tumor site with treatment-planning software to determine beam direction and intensity, accounting for tumor motion and anatomy changes during the treatment procedure.

Stereotactic spine radiotherapy

Stereotactic spine radiotherapy uses guidance from CT scans for the highest possible dose to tumors on the spine. The CT machine moves around the treatment table to constantly confirm the tumor location. Radiation beams can be instantly adjusted to account for any changes during the procedure.

Volumetric modulated arc therapy (VMAT)

VMAT is a form of IMRT in which multiple radiation beams of different intensities are directed at the tumor through a rotating radiation treatment machine. As the machine rotates, radiation is delivered at every angle, focusing the highest possible dose of radiation to the tumor while minimizing radiation to surrounding healthy organs.