Radiation Therapy

Introduction

About the Cervix

The use of high-energy x-rays or other particles to destroy cancer cells. The most common type of radiation treatment is called external-beam radiation therapy, which is radiation given from a machine outside the body. When radiation treatment is given using implants near the cancer cells, it is called internal radiation therapy or brachytherapy.

Radiation oncologists use radiation therapy to destroy cancer cells and slow tumor growth while limiting the harm to nearby healthy tissue.

More than half of people with cancer receive some type of radiation therapy. For some cancers, radiation therapy alone is an effective treatment. Other types of cancer respond best to combination treatments, which is using more than 1 treatment for a patient’s treatment plan. For instance, this may include radiation therapy plus surgery, chemotherapy, or immunotherapy.

What is external-beam radiation therapy?

External-beam radiation therapy is the most common type of radiation therapy. It delivers radiation from a machine outside the body. It can treat large areas of the body, if needed.

A machine called a linear accelerator, or linac, creates the radiation beam for x-ray or photon radiation therapy. Special computer software adjusts the beam’s size and shape. This helps target the tumor while avoiding healthy tissue near the cancer cells.

Most treatments are given every weekday for several weeks. Form-fitting supports or plastic mesh masks are used for radiation therapy to the head, neck, or brain to help people stay still during treatment.

The types of external-beam radiation therapy are:

Three-dimensional conformal radiation therapy (3D-CRT). Detailed 3-dimensional pictures of the cancer are created, typically from computed tomography (CT) or magnetic resonance imaging (MRI) scans. This allows the treatment team to aim the radiation therapy more precisely. It often means that they can safely use higher doses of radiation therapy while reducing damage to healthy tissue. This lowers the risk of side effects. For instance, dry mouth is common after radiation therapy for head and neck cancer. But 3D-CRT can limit the damage to the salivary glands that causes dry mouth.

Intensity modulated radiation therapy (IMRT). This is a more complex form of radiation. With IMRT, the intensity of the radiation is varied within each field unlike conventional 3D-CRT, which uses the same intensity throughout each beam. IMRT targets the tumor and avoids healthy tissue better than conventional 3D-CRT.

Image-guided radiation therapy (IGRT). This refers to the practice of using daily images of each treatment field to confirm patient positioning and make sure the target is in the field. These daily images are compared to the images used to plan treatment. IGRT allows your doctor to make each treatment field smaller. This allows better targeting of the tumor and helps reduce damage to healthy tissue.

Tomotherapy is a radiation therapy modality, in which the patient is scanned across a modulated strip-beam, so that only one “slice” of the target is exposed at any one time by the linear accelerator (linac) beam. 

Stereotactic radiation therapy/radiosurgery (SRT/SRS). This treatment delivers a large, precise radiation therapy dose to a small tumor area. The patient must remain very still. Head frames or individual body molds help limit movement. SRT is often given as a single treatment or in fewer than 10 treatments. Some patients may need more than one course of SRT. 

Proton beam therapy. This treatment uses protons rather than x-rays. A proton is a positively charged particle. At high energy, protons can destroy cancer cells. The protons go to the targeted tumor and deposit the specific dose of radiation therapy. Unlike with x-ray beams, there is very little radiation dose beyond the tumor. This limits damage to nearby healthy tissue.

What is internal radiation therapy?

Internal radiation therapy is also called brachytherapy. This type of radiation therapy is when radioactive material is placed into the cancer or surrounding tissue. Implants may be temporary or permanent and may require a hospital stay.

Types of internal radiation therapy include:

Temporary internal radiation therapy. This is when radiation therapy is given in one of these ways:

  • Needles
  • Tubes, called catheters
  • Special applicators

The radiation stays in the body for anywhere from a few minutes to a few days. Most people receive radiation therapy for just a few minutes. Sometimes, people receive internal radiation therapy for more time. If so, they stay in a private room to limit other people’s exposure to the radiation.

Permanent implants. These are tiny metallic seeds that contain radioactive material. The capsules are about the size of a grain of rice. They deliver most of the radiation therapy around the implant area. But some radiation may exit the patient’s body. This requires safety measures to protect others from radiation exposure. Over time, the implants lose radioactivity. And the inactive seeds remain in the body.

Tomotherapy