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


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

Vanneste, B.; van Wijk, Y.; Lutgens, L.; van Limbergen, E.; van Lin, E.; van de Beek, K.; Lambin, P.; Hoffmann, A.

Background and Purpose:

To assess the effect of a shrinking rectal balloon implant (RBI) on the anorectal dose and complication risk during the course of prostate radiotherapy.

Material/Methods:

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 75 Gy isodose (V75Gy) was calculated as well as the mean anorectal dose. The increase in risk of grade 2-3 late rectal bleeding (LRB) between the start and end of treatment was predicted.

Results:

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 correlation between mean anorectal dose and balloon deflation was found. No significant increase in V75Gy and increase in LRB risk over time was observed, except in one patient whose RBI had completely deflated in the third week of treatment.

Conclusions:

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.

Keywords: Prostate cancer; Radiotherapy; Rectal Balloon Implant; Volume stability; Rectal Dose; Rectal Toxicity

Permalink: https://www.hzdr.de/publications/Publ-25612
Publ.-Id: 25612