Brachytherapy (Internal Radiation Therapy)

The radiation source is implanted in the tumor itself (interstitial brachytherapy, used for example in prostate cancer), placed inside a body cavity or a cavity left by surgery, such as the uterus or vagina (intracavitary brachytherapy, used in cervical and endometrial cancers), or attached to the surface of the eye (episcleral brachytherapy, used for eye melanoma). A related technique, radioembolization, delivers radioactive beads into the blood vessels of the liver. Because radiation intensity drops sharply with distance, the tumor receives a very high dose while tissues even a short distance away are largely spared. The dose can be given at different rhythms. In high-dose-rate (HDR) brachytherapy a strong source stays in place for only about 10 to 20 minutes per session, with sessions repeated over days or weeks. In low-dose-rate (LDR) treatment the source remains in the body for 1 to 7 days, usually during a hospital stay, and is then removed. Permanent implants — such as prostate seeds — stay in the body for life, but their radiation weakens each day until it is negligible; while it is still active, contact with visitors, pregnant women, and small children may be temporarily limited.