From the Greek "brachy" (close) and "therapy" (treatment). Brachytherapy is a method of inserting radioactive pharmaceutical-medical devices into malignant or benign tumors as a treatment. For example, the brachytherapy is used to treat prostate cancer. Tiny titanium tubes are filled with itsy-bitsy titanium balls that have been radioactively labeled with Iodine-125; the tubes are sealed, tested for leakage, and the level of radioactivity is measured. A doctor prescribes the number of tubes and strength of the doseage. Brachytherapy works best when the cancer has an intermediate rate of growth (low Gleason grade) and is in Stage II or III. Brachytherapy has a lower rate of side effects, such as impotence, than do surgery or external radiation beam treatment.