A Novel Biodegradable Balloon (Bioprotect Spaceguard) Provides Reproducible Geometry and Significantly Reduces Rectal Dose in Patients Receiving IMRT for Prostate Cancer: Single Arm Phase I Multi-Institutional International Study

Results: The procedure was tolerated well without any significant discomfort from the procedure or placement. There was no procedure or balloon related Adverse Effect. The balloon displaced both the prostate post wall (mean: 11.4mm; range: 5mm18.7mm) and anterior rectal wall (mean: 10.8mm; range: 6mm-16mm) along the interface while the anterior surface of the prostate and posterior surface of the rectum got displaced negligibly (mean: 4.8mm; range: 0.2mm-12.3mm). The prostate was elongated in the superior-inferior dimension but its volume was constant throughout. There was non-significant change in balloon volume and position, prostate posterior wall and rectal anterior wall throughout treatment. The balloon seemed to serve as buffer for prostate inter-fraction displacement from changes in rectal volume. The mean gap introduced by the balloon was 25.7 mm (range: 13.6mm-32.7mm) and it remained constant during treatment. This gap resulted in a mean V65 of 4.255% (range: 0%11.69%) compared to 14.45% (range: 11.14%-20.52%) before implant. Similarly, V70 changed from 12.15% (range: 9.3%17.11%) to 2.95% (range: 0%-9.69%). Follow up scans showed degradation of the balloon 90 days post treatment. Conclusions:Bioprotect is safe, easy to insert and creates a highly reproducible and uniform space between prostate and anterior rectal wall. This technique has tremendous implications for dose escalation and hypofractionation in radiation therapy. Author Disclosure: M.K. Garg: None. G. Kovacs: F. Consultant/Advisory Board; Bioprotect. D.M. Blakaj: None. N. Tsai: None. E. Gez: None. G. Scarzello: None. I. Koziol: None. M. Anscher: None. A. Paz: E. Ownership Interest; Co-founder Bioprotect. S. Kalnicki: None.