Improvement of transperineal implant dosimetry by intraoperative cystoscopic confirmation of prostate anatomy

Purpose: A simple, inexpensive method to aid in the accurate placement of permanent seeds for prostate brachytherapy is described. The effect of identifying the prostate base and apex cystoscopically relative to registration seeds placed at the beginning of the implant is discussed. Materials and Methods: At the beginning of each implant procedure a pair of marker seeds are first placed in the prostate, including 1 seed at the base and 1 at the apex. Using a cystoscope, the urologist identifies the prostatic base and apex, and a fluoroscopic record is obtained. The positions of the base and apex relative to the marker seeds are monitored throughout the case via fluoroscopy to aid in needle and seed placement for the implant. Results: Use of this method significantly improved coverage of the prostate apex, reduced overall dose variance in the prostate base and improved overall gland dosimetry by 22% as measured by the D90 quality metric (minimal dose which covers 90% of the prostate volume). Conclusions: While the clinical efficacy of improved target coverage on local control and survival awaits further clinical investigation, we encourage others to adopt this easy technique to ensure better, more consistent interstitial implants.