What is brachytherapy?

Brachytherapy is internal radiation therapy that uses a solid radiation source. As the National Cancer Institute describes it, "seeds, ribbons, or capsules that contain a radiation source are placed in your body, in or near the tumor."

The name explains the idea. StatPearls, a peer-reviewed clinical reference on the National Library of Medicine's shelf, notes that brachy comes from the Greek for short distance. Radiation weakens quickly as it travels away from its source. Put the source inside the tumor and the tumor absorbs an enormous dose, while tissue an inch away absorbs far less. External beam radiation has to aim through healthy skin, muscle, and organs to reach a tumor. Brachytherapy skips most of that trip.

How it is delivered

A catheter or applicator goes in first. NCI puts it simply: "Your doctor will place the catheter or applicator into your body before you begin treatment." Only then is the radiation source loaded. Machines called remote afterloaders push the source into place once staff have left the room, which keeps the team's own exposure near zero.

There are three placement routes. Interstitial means the source sits inside the tumor tissue itself, as with prostate seeds. Intracavitary means an applicator sits in a body cavity, which is the usual approach for cervical cancer. Intraluminal means the source travels inside a tube, such as the airway or the esophagus.

Three schedules, three very different weeks

Low-dose-rate treatment delivers roughly 0.4 to 2.0 gray per hour. Gray, written Gy, is the unit for absorbed radiation dose. NCI says these implants stay in place "for 1 to 7 days," usually with a hospital stay.

High-dose-rate treatment runs above 12 gray per hour. The source is in the body "for just 10 to 20 minutes at a time and then taken out." That happens "twice a day for 2 to 5 days or once a week for 2 to 5 weeks," and it is normally an outpatient visit.

Permanent implants are different again. The seeds go in and the catheter comes out. NCI explains that "the implants remain in your body for the rest of your life, but the radiation gets weaker each day." Iridium-192 is the workhorse for high-dose-rate treatment. Iodine-125, palladium-103, and cesium-131 are common in permanent seeds.

NCI lists the usual targets as cancers of the head and neck, breast, cervix, prostate, and eye. StatPearls adds soft tissue sarcoma. One partial-breast schedule gives 34 Gy in ten treatments over five days, two per day.

The part that surprises people

You may give off radiation for a while. NCI states this directly, and it is the main way brachytherapy differs from external beam, which leaves nothing behind. While a temporary source is in place, you stay in a private hospital room. Visits are held to "about 30 minutes or less each day." Pregnant women and children younger than a year old are asked not to visit at all. With permanent seeds, NCI says you may need to limit your time around other people when the radiation is first put in place, and to be extra careful not to spend time with children or pregnant women. Your team will say how long that lasts.

You get pain medicine before the catheter or applicator is removed. NCI also warns that the area "might be tender for a few months" afterward.

If brachytherapy has been offered, the useful question is which of the three schedules is planned. The difference between a week in a hospital bed, a handful of short outpatient visits, and an implant you keep for life is worth knowing before you agree.