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Radiation therapy
Source: Retinoblastoma Treatment (PDQ®)–Patient Version, National Cancer Institute.
Source updated: October 7, 2021 · Captured 2026-09-09.
Selected source text with whitespace normalised. This Triangle page is not an NCI PDQ summary. Independent clinical review is pending.
Context: Treatment Option Overview / Six types of standard treatment are used:
Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells or keep them from growing. There are two types of radiation therapy:
External-beam radiation therapy uses a machine outside the body to send radiation toward the area of the body with cancer. Certain ways of giving radiation therapy can help keep radiation from damaging nearby healthy tissue. These types of radiation therapy include the following:
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External-beam radiation therapy uses a machine outside the body to send radiation toward the area of the body with cancer. Certain ways of giving radiation therapy can help keep radiation from damaging nearby healthy tissue. These types of radiation therapy include the following:
Intensity-modulated radiation therapy (IMRT): IMRT is a type of 3-dimensional (3-D) external radiation therapy that uses a computer to make pictures of the size and shape of the tumor. Thin beams of radiation of different intensities (strengths) are aimed at the tumor from many angles.
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External-beam radiation therapy uses a machine outside the body to send radiation toward the area of the body with cancer. Certain ways of giving radiation therapy can help keep radiation from damaging nearby healthy tissue. These types of radiation therapy include the following:
Proton beam radiation therapy: Proton beam radiation therapy is a type of high-energy, external radiation therapy that uses streams of protons (tiny particles with a positive charge) to kill tumor cells. This type of treatment can lower the amount of radiation damage to healthy tissue near a tumor.
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Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer. Certain ways of giving radiation therapy can help keep radiation from damaging nearby healthy tissue. This type of internal radiation therapy may include the following:
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Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer. Certain ways of giving radiation therapy can help keep radiation from damaging nearby healthy tissue. This type of internal radiation therapy may include the following:
Plaque radiotherapy: Radioactive seeds are attached to one side of a disk, called a plaque, and placed directly on the outside wall of the eye near the tumor. The side of the plaque with the seeds on it faces the eyeball, aiming radiation at the tumor. The plaque helps protect other nearby tissue from the radiation.
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Whether internal or external radiation therapy is given depends on the stage of the cancer being treated, where it is found in the body, and how the cancer responded to other treatments.
Preserved source evidence · Independent clinical review pending · Not medical advice