Real-time optimized intraoperative dosimetry for prostate brachytherapy: a pilot study

To assess the feasibility of real-time intraoperative treatment planning for permanent prostate brachytherapy analyzing the impact on operative time and adequacy of postimplant dosimetry.

Seventeen consecutive patients undergoing permanent brachytherapy for prostate cancer had real-time intraoperative computer-based and optimized treatment planning. The first 8 patients were implanted using a plan generated before the surgery and served to assure the team qualitatively that this could be performed without greatly increasing intraoperative time. They served as control group for expected achieved dosimetry results reviewing the D90, V100, V150 parameters from the dose-volume histograms. The next 9 patients were implanted according to the real-time plan. The times needed to carry out various steps of the procedure were recorded. The achieved dosimetry was then compared to the control group to assure that accuracy was unchanged.

The median operative time for patients undergoing intraoperative dosimetry was 57 min. Of this, 21 min were devoted to anesthesia and nursing functions. Postoperative dosimetry showed a median achieved V100 (volume of prostate receiving 100% of prescribed dose) of 97% for the control group. For the real-time dosimetry group, the median V100 was similar at 94%. The V150 (volume receiving 150%) is 49% for both groups. The D90 (dose received by 90% of the target) was normalized for easy comparison and was consistently slightly greater than the prescription dose.

Treatment planning for permanent brachytherapy of prostate cancer has historically been performed as a computer-generated and optimized plan run weeks in advance of an implant, or according to a set pattern using an intraoperative nomogram. These data show that planning can now be optimized intraoperatively using widely available software without compromising the operative time or implant quality.