Interobserver variability in rectum contouring in high-dose-rate brachytherapy for prostate cancer: A multi-institutional prospective analysis

Autores de IIS La Fe

• Francisco Javier Celada Álvarez

  Autor

• Susana Roldan Ortega

  Autor

• Blanca Ibañez Rosello

  Autor

• Alejandro Tormo Mico

  Autor

• José María Benlloch Baviera

  Autor

• José Pérez Calatayud

  Autor

Participantes ajenos a IIS La Fe

• Chicas-Sett, R
• Rodriguez-Villalba, S
• Santos-Olias, M
• Soler-Catalan, P
• Arribas, L

Grupos

• Núcleo de investigación traslacional integrado Urológico de Valencia (NITIUV)

  

  Leader

  César David Vera Donoso

• Unidad Mixta de Investigación en Radiofísica e Instrumentación nuclear en medicina

  Leader

  Facundo Ballester Pallares

Abstract

PURPOSE: The aim of this study was to evaluate the interobserver variability (KW) of rectum contouring, and its dosimetric consequences, for high-dose-rate brachytherapy in patients with prostate cancer across multiple institutions. METHODS AND MATERIALS: Five radiation oncologists contoured rectums in 10 patients on transperineal ultrasound image sets after establishing a delineation consensus. The D-0.1cc, D-1cc, and D-2cc rectum volume parameters were determined. The mean, standard deviation, and range of each dose-volume histogram parameter were evaluated for each patient. The JOY was determined using the coefficient of variation, and the dosimetric impacts on the total dose were analyzed by estimating the biologically equivalent dose (EQD(2 alpha/beta) = 3). RESULTS: The interobserver coefficients of variation (+/- standard deviation) for the reported D-0.1cc, D-1cc, and D-2cc were 5 +/- 1.84%, 4 +/- 1.26%, and 4 +/- 1.33%, respectively. As for the impact on the total dose, the mean dose differences for D-0.1cc, D-1cc, and D-2cc were 10 Gy, 7.3 Gy, and 6.6 Gy, respectively. CONCLUSIONS: The D-2cc is robust as evident by the low IOV (<5%). However, some variability ranges almost overlap with the clinical threshold level, which may present dosimetric and clinical complications. General rectal contouring guidelines for prostate high-dose-rate brachytherapy are desirable to reduce discrepancies in delineation. (C) 2017 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Keywords

• Contouring; High-dose-rate brachytherapy; Interobserver variability; Prostate cancer