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About Cesium-131
Brachytherapy for Prostate Cancer
There are two types of prostate cancer radiation treatments. Internal placement of radioactive sources is known as brachytherapy. The word “brachytherapy” derives from the Greek prefix “brachy”, meaning short or close to, because of the proximity of the radioactive sources to the malignancy. Radiation delivered externally using electronically generated x-rays is known as external beam radiation (EBRT). These treatments are delivered using a device known as a linear accelerator that directs the x-ray beam at the target.
Brachytherapy may be delivered using permanent or temporary placement of radioactive sources. Permanent brachytherapy utilizes isotopes that deliver continuous radiation to the targeted site over a period of weeks to months. This is also known as low dose rate (LDR) brachytherapy. Permanent seed brachytherapy for prostate cancer uses tiny implants called “seeds”. The seeds themselves are 4-5 mm in length with a diameter similar to a grain of rice. The radioactive element called an “isotope” is housed inside a titanium casing. During implantation the seeds are inserted directly into the prostate through thin, hollow needles. The seeds give off radiation for a period of time and ultimately become non-radioactive. The inactive seeds remain within the prostate permanently. Temporary placement of radioactive sources for prostate cancer is known as high dose rate (HDR) brachytherapy. In this procedure, catheters are placed into the prostate gland. A highly radioactive source is then introduced into the prostate through the catheters usually for a period of several minutes. The radioactive source is then removed. This procedure is repeated several times with at least six hours between treatments. At the conclusion of the treatment the catheters are removed.
The treatment of prostate cancer using brachytherapy has been around since it was first reported by Pasteau in 1911 2. The main obstacle for permanent seed brachytherapy in its infancy was lack of an effective way to see where the seeds were being placed. The lack of imaging capability resulted in under and over dosing of the prostate. In the last 10 to 15 years advances in ultra-sound-guided transperineal techniques and computer-optimized planning has made seed placement and dose delivery in brachytherapy very accurate and reliable resulting in excellent long-term biochemical control. Today permanent seed brachytherapy is recognized as an established treatment intervention for localized prostate cancer with projected long-term outcomes comparable to outcomes achieved with radical prostatectomy and external beam radiotherapy 3. In 2007 more than 60,000 men will choose permanent seed brachytherapy to treat their prostate cancer 4.
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