3317 - An Intermittently Inflated Large-Volume Balloon Spacer for Protecting Rectum during Prostate Cancer Radiotherapy: Initial Animal Study

12:45pm - 02:00pm PT

Hall F

Screen: 21

POSTER

Presenter(s)

Xin Qi, MD, MS - Peking University First Hospital, Beijing, Beijing

X. Qi¹, Y. Liu², H. Zhang¹, Y. Gao¹, Q. H. Peng¹, and H. Z. Li¹; ¹Department of Radiation Oncology, Peking University First Hospital, Beijing, China, ²Department of Urology, Peking University First Hospital, Beijing, China

Purpose/Objective(s):

Hydrogel and balloon spacers are both clinically utilized for rectal dose reduction in prostate cancer radiotherapy (RT). Compared to hydrogel, the space created by the balloon spacer is more symmetrical and the separation is greater. However, increased separation also means increased compression on surrounding tissues. In practice, the daily RT delivering time is very brief, and tissue separation outside of treatment times is unnecessary and can cause discomfort and additional risks for patients. Therefore, intermittent large-volume separation only during RT delivering is a more reasonable strategy, particularly for patients undergoing hyper-fractionated RT.

Materials/Methods:

An in vivo inflatable balloon spacer was developed to provide intermittent separation between prostate and rectum during RT delivering. The balloon can be inflated and deflated through a subcutaneously implanted port. The balloon spacers were transperineally implanted in 6 dogs, which received 36.25 Gy in 5 fractions to the PTV of prostate.

Results:

All 6 animals successfully underwent balloon implantation with a mean procedure time of 20.5 minutes. The balloon was inflated prior to each treatment session and partially deflated immediately after completion of therapy. Daily pre-treatment CBCT imaging consistently monitored the separation distance and balloon migration, revealing a mean distance of 21.2±7.9 mm. Daily inflation-deflation cycles demonstrated no significant positional displacement of the balloon and maintained consistent volumetric stability throughout the treatment course. Pre-to postspacer plans had a significant reduction in mean rectal V36.25 (9.4% to 0.3%, P<.0001). After the final treatment session, the balloons were retrieved. During the 3-month follow-up period, no systemic or local adverse reactions were detected in the experimental animals.

Conclusion:

This novel inflatable balloon spacer was safe and effective for its intended use of intermittent large-volume separation of rectum during hyper-fractionated RT. A clinical study will commence to evaluate the safety and efficacy of this device during RT in patients with prostate cancer.