Three-dimensional conformal brachytherapy for prostate cancer.

Because innovations in radiation treatment planning have dramatically improved the precision of external beam radiotherapy for prostate cancer with the advent of conformal three-dimensional conformal therapy and intensity modulated radiotherapy, similar developments are emerging for prostate brachytherapy. Computer software programs are facilitating the ability to rapidly create conformal treatment plans in the operating room, taking into account the three-dimensional reconstruction of the prostate target and adhering to dose-volume constraints of the normal tissues including the urethra and rectum. Although excellent dose distributions can be achieved with pre-planning techniques, intraoperative planning takes into account the intraoperative geometry of the prostate and the surrounding normal tissues and can consistently produce seed implants with reduced urethral and rectal doses while delivering the intended prescription dose to the target volume. Current developments are pursuing methods to dynamically modify the treatment plan as the implant procedure is ongoing based on the coordinates of the deposited seeds. Such approaches will minimize the possibility of tumor underdosage and further enhance the conformality of prostate brachytherapy.