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What Is A Brachytherapy Seed?

Tiny Seeds of Cancer Destruction

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Updated February 22, 2010

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Radiation for brachytherapy is generated by tiny pieces of radioactive material, called seeds or pellets. Radiation oncologists use these seeds, also called the source, to deliver a dose of radiation to a tumor or the surgical cavity left after a tumor has been removed. Brachytherapy seeds may be permanently left in the body, or placed temporarily for short periods of time.

A brachytherapy seed may be the size of a dried rice grain or a bit of lead from a mechanical pencil. Brachytherapy seeds are made of Iodine 125, Palladium 103, Thulium 170, and Iridium 194 isotopes.

Origins of The Brachytherapy Seed

Brachytherapy - radiation treatments from sources placed inside the body - is an idea that originated from the research of Marie and Pierre Curie. Marie Curie discovered polonium and radium, the radioactive elements for which she was given the Nobel Prize. Her husband, Pierre Curie, was the first to suggest that implanting a small seed of radioactive material into a tumor might shrink it.

Seeds Kill Cancer Cells

Brachytherapy seeds fight cancer right where it lives. Each seed emits ionizing radiation energy. When poorly organized cancer cells are scrambled by radiation, they can't grow and divide very well. The radiating energy from brachytherapy seeds damages or kills nearby cancer cells by breaking their genetic instructions. Healthy cells will also be affected by seed radiation, but they are usually robust enough to repair themselves and recover normal life cycles.

Uses of Brachytherapy Seeds

Brachytherapy seeds may be used to treat several types of cancer. Prostate cancer can be treated with permanent brachytherapy, placing many seeds into the tumor area and allowing them to emit radiation for a few weeks or months until they are no longer active. Where the body has a natural cavity, such as with cancers of the uterus, vagina, rectum, or chest, a container for brachytherapy seeds may be temporarily placed for treatment. Early-stage breast cancer can be treated with high-dose rate (HDR) intracavity or interstitial brachytherapy. In these cases, soft catheters or balloons will be used to accommodate the brachytherapy seeds for the few minutes that each treatment is given.

Sources:

How Is Radiation Given? American Cancer Society. Last Revised: 07/17/2009.

Radiation Therapy for Cancer: Questions and Answers. National Cancer Institute. Reviewed: 08/25/2004.

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