Comparison of intraoperative ultrasound with postimplant computed tomography–dosimetric values at Day 1 and Day 30 after prostate brachytherapy

Ohashi, Toshio; Yorozu, Atsunori; Toya, Kazuhito; Saito, Shiro; Momma, Tetsuo; Nagata, Hirohiko; Kosugi, Michio; Shigematsu, Naoyuki; Kubo, Atsushi

doi:10.1016/j.brachy.2007.08.006

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Volume 6, Issue 4 , Pages 246-253, October 2007

Comparison of intraoperative ultrasound with postimplant computed tomography–dosimetric values at Day 1 and Day 30 after prostate brachytherapy

Toshio Ohashi
- Department of Radiology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
- Department of Radiology, Keio University, School of Medicine, Tokyo, Japan
- Corresponding author. Department of Radiology, Keio University, School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan. Tel.: +81-3-3353-1211; fax: +81-3-3359-7425.
Atsunori Yorozu
- Department of Radiology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
Kazuhito Toya
- Department of Radiology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
Shiro Saito
- Department of Urology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
Tetsuo Momma
- Department of Urology, National Hospital Organization Saitama Hospital, Saitama, Japan
Hirohiko Nagata
- Department of Urology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
Michio Kosugi
- Department of Urology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
Naoyuki Shigematsu
- Department of Radiology, Keio University, School of Medicine, Tokyo, Japan
Atsushi Kubo
- Department of Radiology, Keio University, School of Medicine, Tokyo, Japan

Received 11 May 2007; received in revised form 6 July 2007; accepted 23 August 2007. published online 25 October 2007.

Abstract

Purpose

To compare the results of intraoperative dosimetry with those of postimplant computed tomography (CT)-based dosimetry after ¹²⁵I prostate brachytherapy.

Methods and materials

We treated 412 prostate cancer patients with ¹²⁵I prostate brachytherapy, with or without external beam radiotherapy at our institution. Neoadjuvant hormone therapy was administered to 331 patients (80.3%). Implantation was performed using an intraoperative interactive technique. Postimplant dosimetry was performed on Day 1 and Day 30 using CT imaging. The dosimetric results for the prostate, urethra, and rectum were compared among intraoperative ultrasound, and CT scans of Day 1 and Day 30.

Results

The mean intraoperative minimal dose received by 90% of the prostate volume (D₉₀) was 118.8% of the prescribed dose vs. 106.4% for Day 1 (p<0.01) and 119.2% for Day 30 (p=0.25). There were no significant correlations between the intraoperative D₉₀ and the postimplant D₉₀ values (intraclass correlation coefficients=0.42 and 0.33 for Day 1 and Day 30, respectively). Prostatic edema at Day 1 had the largest effect on the Day 1 D₉₀ (p<0.01). The factor significantly affecting the Day 30 D₉₀ was neoadjuvant hormone therapy (p<0.01). The mean Day 30 D₉₀ for the hormone-treated patients was 117.9%, compared with 124.6% for those who remained hormone naïve. The intraoperative and postimplant dosimetric values differed significantly for the urethra and rectum.

Conclusions

Our results demonstrate that there are no significant differences between the D₉₀ assessments obtained intraoperatively and at Day 30 postoperatively. Furthermore, there are no definite correlations between intra- and postimplantation dosimetric values. Other D₉₀ values differed significantly between the intraoperative and postimplant dosimetry. This study suggests that dosimetry has negligible clinical utility for informing patients, at discharge, of whether or not their implants are adequate.

Keywords: Prostate cancer, Brachytherapy, Iodine-125, Intraoperative, Dosimetry