Editing Management of Localized Prostate Cancer (section)

==== Brachytherapy ====
* '''Brachytherapy (“short” therapy) is the placement of radioactive sources into or near tumors for therapeutic purposes'''
* The goal of prostate brachytherapy is to deliver a homogeneous dose to the prostate while minimizing dose to nearby sensitive normal structures such as the rectum and urethra; seeds should be distributed evenly throughout the gland with periurethral sparing. Radioactive sources (seeds or needles) are implanted directly into the prostate gland, sometimes into the surrounding tissues
* There is no preferred isotope for brachytherapy.
** The most commonly used permanent implants are iodine-125 (125I), palladium-103 (103Pd), or cesium-131 (131Cs) seeds.
* '''Assessment of permanent implant quality'''
** '''Post-implant dosimetry in these dose-limiting regions is important to assess implant quality.'''
*** '''Post-implantation CT''' with or without MRI '''is performed to determine seed localization and reference the dose to the prostate and other structures of importance. A significant source of error in these calculations is prostatic edema, which is invariably observed after implantation'''
** Dosimetry can be adversely affected by poor implantation or migration of the seeds after implantation
* '''<span style="color:#ff0000">Brachytherapy radiation dose and fields</span>'''
** '''<span style="color:#ff0000">The doses delivered to the prostate substantially higher than those for EBRT:</span> ≈145 Gy for iodine and 125 Gy for palladium'''
*** '''Although the prostate itself can tolerate high doses of radiation, the rectal toxicity limits the dose that can be given in brachytherapy'''
* '''Brachytherapy Combined with ADT'''
** '''ADT should not be added to brachytherapy except to reduce the size of the prostate to allow the dosimetry to be optimized'''
*** In patients who have an enlarged prostate gland, it can be technically challenging to implant the entire prostate volume, especially anteriorly. Accordingly, patients are often treated with ADT to shrink the prostate before brachytherapy is performed.
*** There are no randomized trials demonstrating a survival benefit from adding ADT to low-dose rate or high-dose rate brachytherapy monotherapy
* '''Brachytherapy Combined with External Irradiation'''
** '''Although outcomes in patients with low-risk prostate cancer using brachytherapy are excellent, biochemical control can be improved for intermediate-risk and the higher risk subset of intermediate-risk patients by combining brachytherapy with EBRT;''' the role of EBRT + brachytherapy versus brachytherapy alone for selected intermediate-risk men is being investigated in a randomized clinical trial by RTOG 0232
** '''The brachytherapy is usually given first''', so that the EBRT can be discontinued if the patient begins to experience toxicity
* '''High-dose-rate (HDR) Brachytherapy'''
** Permanent seed implantation delivers a dose over a number of weeks to months depending on the isotope chosen, hence the term low dose rate. An alternative method of brachytherapy, which delivers short but high doses of radiation using temporary catheters, is HDR brachytherapy.
** HDR has been used primarily as a boost in combination with EBRT for patients with intermediate-risk or high-risk features, although it is becoming more common as monotherapy in patients with low-risk disease.
** '''HDR brachytherapy as a monotherapy has been reported to achieve results similar to EBRT in intermediate-risk prostate cancer'''