All types of radiation therapy use ionizing radiation to kill cancer cells. The oldest and still the most commonly used form of radiotherapy is external beam therapy, in which an external source of radiation is targeted to a patient’s tumor. One of the principle problems with this type of radiotherapy is that it is not highly specific. Many people who receive this therapy find that healthy tissue is also damaged, leading to painful side effects.
Brachytherapy is an entirely different type of radiation therapy with some particular advantages over external beam therapy. Also called sealed source therapy, this treatment involves the placement of tiny radioactive rods – called seeds – next to or inside a tumor. The seeds emit radiation over very short distances, meaning that the radiation is very specifically targeted to cancer cells.
The main advantage of this treatment is that side effects and toxicity are greatly reduced compared to external beam radiation, due to the ability to target cancer cells with greater specificity. Although toxic side effects are reduced in general, using brachytherapy to treat prostate cancer may cause infertility or impotence.
Another advantage is that the methods used to implant seeds are usually non-invasive, and are not physically demanding.
Brachytherapy is most often used to treat localized tumors in people with prostate cancer, cervical cancer, some types of mesothelioma, head or neck cancers, skin cancers, and several others.
Brachytherapy seeds are tiny – around the size of a grain of rice – and can be implanted in the body via a needle. This type of implantation is not suitable for all types of cancer; in some cases seeds are placed in a container, which is surgically implanted within or next to a tumor or within a body cavity.
Brachytherapy treatment can be either temporary or permanent. The temporary treatment involves the placement of seeds for a short interval, after which they are removed. In permanent treatment, the seeds are implanted and then allowed to stay in the body permanently. Seeds implanted permanently give off radiation for between three and twelve months depending on the dosage.
American Brachytherapy Society
Brachytherapy information at the Radiological Society of North America, Inc.
The Mayo Clinic on Brachytherapy