A nomogram to compensate for intraoperative prostate edema during transperineal brachytherapy.
Maneno muhimu
Kikemikali
OBJECTIVE
Prostate edema during and following prostate brachytherapy may have a negative impact on implant dosimetry. The purpose of this study was to assess the magnitude of prostate edema during the operative procedure and to develop a nomogram of isotope activity required for compensation of such intraoperative prostate volume changes.
METHODS
Twenty-five consecutive patients with early-stage, localized adenocarcinoma of the prostate underwent ultrasound-guided transperineal interstitial permanent prostate brachytherapy with either iodine 125 or palladium 103. Transrectal ultrasound volume studies of the prostate were performed before and during the implant procedure. Computed tomography-based postimplant dosimetry was performed 3-4 weeks after surgery.
RESULTS
A median intraoperative prostate volume increase after insertion of applicator needles of 10.4% (range 1.2-32.5%) was identified. A correlation of -0.55 (95% confidence interval -0.78 to -0.19) between the minimum dose covering 90% of the prostate volume (%D90) and the amount of edema was identified. An algorithm and nomogram was developed to calculate the extra isotope activity necessary to compensate for intraoperative edema.
CONCLUSIONS
Prostate edema occurs at the time of transperineal needle placement. A negative correlation was found between the amount of edema and dose coverage of the prostate (%D90). Therefore, to cover the prostate volume adequately, additional isotope activity is required when preoperative treatment planning is performed. This nomogram can be used to compensate for such volume changes.
