Dynamics of rectal balloon implant shrinkage in prostate VMAT: Influence on anorectal dose and late rectal complication risk

Ben G. L. Vanneste*, Y. van Wijk, L. C. Lutgens, E. J. Van Limbergen, E. N. van Lin, K. van de Beek, P. Lambin, A. L. Hoffmann

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

12 Citations (Web of Science)

Abstract

To assess the effect of a shrinking rectal balloon implant (RBI) on the anorectal dose and complication risk during the course of moderately hypofractionated prostate radiotherapy. In 15 patients with localized prostate cancer, an RBI was implanted. A weekly kilovolt cone-beam computed tomography (CBCT) scan was acquired to measure the dynamics of RBI volume and prostate-rectum separation. The absolute anorectal volume encompassed by the 2 Gy equieffective 75 Gy isodose (V-75Gy) was recalculated as well as the mean anorectal dose. The increase in estimated risk of grade 2-3 late rectal bleeding (LRB) between the start and end of treatment was predicted using nomograms. The observed acute and late toxicities were evaluated. A significant shrinkage of RBI volumes was observed, with an average volume of 70.4% of baseline at the end of the treatment. Although the prostate-rectum separation significantly decreased over time, it remained at least 1 cm. No significant increase in V-75Gy of the anorectum was observed, except in one patient whose RBI had completely deflated in the third week of treatment. No correlation between mean anorectal dose and balloon deflation was found. The increase in predicted LRB risk was not significant, except in the one patient whose RBI completely deflated. The observed toxicities confirmed these findings. Despite significant decrease in RBI volume the high-dose rectal volume and the predicted LRB risk were unaffected due to a persistent spacing between the prostate and the anterior rectal wall.
Original languageEnglish
Pages (from-to)31-40
Number of pages10
JournalStrahlentherapie Und onkologie
Volume194
Issue number1
DOIs
Publication statusPublished - 1 Jan 2018

Keywords

  • Volumetric modulated arc therapy
  • Radiotherapy
  • Rectum
  • Volume stability
  • Toxicity
  • MODULATED RADIATION-THERAPY
  • POLYETHYLENE-GLYCOL HYDROGEL
  • EXTERNAL-BEAM RADIOTHERAPY
  • CANCER PATIENTS
  • SPACER APPLICATION
  • ESCALATION TRIAL
  • TOXICITY
  • MULTICENTER
  • INJECTION
  • BRACHYTHERAPY

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