Radiation therapy (also called radiotherapy) is a cancer treatment that uses high doses of radiation to kill cancer cells and shrink tumors. Radiation therapy or radiotherapy is a therapy using ionizing radiation, generally as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radiation oncologists use radiation therapy to destroy cancer cells and slow tumor growth while limiting the harm to nearby healthy tissue.
It is normal to feel worried or overwhelmed when you learn you will need radiation therapy. Learning about this type of treatment may help you feel more prepared and comfortable.
External-beam radiation therapy
External-beam radiation therapy delivers radiation from a machine outside the body. It is the most common radiation therapy treatment for cancer.
This type of radiation therapy targets only the tumor. But it will affect some healthy tissue surrounding the tumor. While most people feel no pain when each treatment is being delivered, the effects of treatment slowly build up over time and may include discomfort, skin changes, or other side effects, depending on where in the body treatment is being delivered. The 2-day break in treatment each week allows your body some time to repair this damage. Some of the effects may not go away until the treatment period is completed.
Types of Radiation Therapy
Doctors can recommend radiation therapy as the first cancer treatment or after surgery or therapies using a medication, like chemotherapy. This is called adjuvant therapy. It targets cancer cells remaining after the initial treatment. When it is not possible to destroy all cancer, doctors may use radiation therapy to shrink tumors and relieve symptoms. This is called palliative radiation therapy.
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.
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 CT or MRI scans.
- Intensity-modulated radiation therapy (IMRT). A more complex form of radiation.
- Proton beam therapy. This treatment uses protons rather than x-rays.
- Image-guided radiation therapy (IGRT). Daily images of each treatment field to confirm patient positioning and make sure the target is in the field.
- Stereotactic radiation therapy (SRT). A large, precise radiation therapy dose to a small tumor area. The patient must remain very still.
Internal Radiation Therapy
Internal radiation therapy is also called brachytherapy. This type of radiation therapy is when radioactive material is placed into cancer or surrounding tissue. Implants may be permanent or temporary and may require a hospital stay.
Each session is quick, lasting about 15 minutes. Radiation does not hurt, sting, or burn when it enters the body. 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.