Trial Information

Improving Assessment (and Ultimately Outcomes) of Permanent Prostate Implant Therapy

This study addresses three major sources of post-implant dosimetry inaccuracy for permanent
prostate implants: post-operative edema, prostate contour delineation, and dose calculation
method. It is hypothesized that a pragmatic edema model can minimize the first
uncertainty, co-registered CT + MR images the second, and an improved dose calculation
algorithm the third.

Detailed objectives are to:

- measure and model the effects of edema on dosimetry;

- evaluate CT + MR image registration methods;

- compare dosimetry for CT alone vs. CT + MRI using the contemporary TG-43 dose
calculation method;

- set up a Monte Carlo code that makes full use of the information in CT + MR images to
perform implant dose calculations;

- compare prostate dosimetry for the Monte Carlo vs. the simpler TG-43 method;

- develop an analytical post-implant dose calculation algorithm for routine clinical use
(Monte Carlo is too slow on a single-CPU brachytherapy planning computer); and finally

- assess the performance of the new algorithm.

Of the estimated 250,000 new cases of prostate cancer in North America in 2004, most are
early stage disease as a consequence of PSA testing. Permanent prostate implant therapy is
a major option for this group, as long-term clinical studies indicate a cure rate equal to
surgery and external beam radiotherapy, but with fewer complications. By dealing with
dosimetric inaccuracies, a proven treatment can reach its full potential.