Review of modern prostate brachytherapy

As computer aided margin tools become more sophisticated, physicists will be increasingly called upon to convert ultrasound prostate volumes to expanded planning target volumes (PTVs) in order to treat adequately extracapsular disease. The AAPM Task Group 43 formalism and the new NIST calibration system suitable for single low energy seeds have been crucial in smoothly implementing changes in established seeds and in Incorporating data from new manufacturers. However, the lack of consensus on treatment design and evaluation has led to an uncomfortably wide spectrum of clinical practice, only part of which can be attributed to variations inherent to any surgical procedure due to the practitioner´s skill. The relative merits of implanting the prostate and margin with a modified uniform seed loading approach to create plans with a relatively homogeneous dose distribution and a corresponding low risk of overdosing critical structures are addressed. Likewise, the advantages of performing postoperative dosimetry at the physically optimum time of greater than two weeks post implant are contrasted with the clinical advantages of obtaining the dosimetry as soon as possible. Proposed lower limits for quality parameters such D₉₀ and V ₁₀₀ are reviewed. Measures of doses to the urethra, rectum and neurovascular bundles are presented along with correlations between various dosimetric parameters and other patient specific data with quality of life metrics involving urinary incontinence, rectal damage and sexual dysfunction