Dosimetric consequences of using a surrogate urethra to estimate urethral dose after brachytherapy for prostate cancer

Hoon K. Lee, Warren D. D'Souza, Jose Miguel J. Yamal, Alan Pollack, Andrew K. Lee, Matthew B. Palmer, Deborah A. Kuban

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

Purpose: To assess the accuracy and dosimetric consequences of defining a surrogate urethra at the geometric center of the prostate in postimplant CT scans. Methods and Materials: Eighty postimplant CT scans were obtained with a Foley catheter in place at Day 0 and at 1 month for 40 patients who had undergone 125I prostate brachytherapy. The percentage of urethral volume receiving at least 275% of the prescribed dose (uV275), uV250, uV200, uV150, maximal dose received by 90% of urethral volume (uD90), uD70, uD30, and uD1 were measured for the Foley catheter and surrogate urethra. The distance between the Foley catheter and surrogate urethra was measured at the base, middle, and apex of the prostate. Results: A statistically significant difference was found in all the above-listed dosimetric parameters between the Foley catheter and surrogate urethra at Day 0 (p ≤ 0.001). At 1 month, the uD90, uD70, and uD1 remained significantly different between the Foley catheter and surrogate urethra (p ≤ 0.05). The difference in the uV275 (p = 0.055) and uV150 (p = 0.059) between the Foley catheter and surrogate urethra showed a trend toward statistical significance at 1 month. The uV250, uV200, and uD30 were greater for the surrogate urethra than for the Foley catheter at 1 month, but were not significantly different statistically. The mean distance between the Foley catheter and the surrogate urethra was greatest at the base (1.2 cm) in the vertical axis at Day 0 and decreased substantially to 0.87 cm at 1 month (p = 0.0004). Conclusion: Using a surrogate urethra at the geometric center of the prostate may significantly overestimate the urethral dose at Day 0 and certain dosimetric parameters at 1 month. An alternative position for a surrogate urethra accounting for the difference in the location of the Foley catheter near the base of the prostate at Day 0 and 1 month could be considered in future studies.

Original languageEnglish (US)
Pages (from-to)355-361
Number of pages7
JournalInternational Journal of Radiation Oncology Biology Physics
Volume57
Issue number2
DOIs
StatePublished - Oct 1 2003
Externally publishedYes

Keywords

  • Postimplant dosimetry
  • Prostate brachytherapy
  • Prostate cancer
  • Surrogate urethra
  • Urethral dose

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Radiation

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