High-precision conformal radiotherapy (HPCRT) of XXXX --a new technique for exact positioning of the prostate at the time of treatment.

@entity1 @entity263 @entity41
PURPOSE: Biopsies taken 2 years after radiotherapy of @entity263 indicate @entity41 cells in 20-60% of cases, and the prognosis for these @entity1 is unfavorable. More precise methods of localization of the prostate are desirable to increase the dose to the @entity263 and minimize the volume of adjacent sensitive tissues that are currently included in the planning target volume. We have sought a method to more accurately locate the prostate at the time of treatment, allowing a reduction of the volume of rectum and bladder included in the high dose region during dose escalation. METHODS AND RESULTS: We have developed a new technique using a special urethral catheter (patent pending), containing markers that can be visualized by the radiotherapy machine for accurate positioning of the prostate. The catheter is used throughout the treatment planning procedure and the isocenter is placed on one of the markers. On the treatment couch the markers are visualized on port-films and with portal imaging immediately before dose delivery. A beam-center-marker on the accelerator makes it possible to adjust the isocenter position to within 1 mm, giving very high precision, independent of external fixation. The technique involves a simple @entity1 setup. The method has been tested in five @entity1 with conventional dose level (70 Gy) and in 24 @entity1 in the first Scandinavian dose escalation study with external beam radiotherapy. No increase in acute side-effects was observed. CONCLUSION: With the new high precision conformal radiotherapy (HPCRT) technique we have developed a technique that allows us to increase the dose to the prostate without excessive side effects. The method reduces the uncertainties in prostate localization, is easy to handle, and feasible in routine treatment.
