3100 - Preclinical Evaluation of a Novel In Situ Biomimetic Mineralization Radioprotective Absorbable Gel for Prostate Cancer Radiotherapy
Presenter(s)
J. Hu1,2, M. Ma3, Y. Liu4, X. Gao3, and F. Lyu3; 1Biomanufacturing and Engineering Living Systems Innovation International Talents Base (111 Base), Beijing, China, 2Biomanufacturing and Rapid Forming Technology Key Laboratory of Beijing, Beijing, China, 3Department of Radiation Oncology, Peking University First Hospital, Beijing, China, 4Department of Urology, Peking University First Hospital, Beijing, China
Purpose/Objective(s):
Radiotherapy is a key curative treatment for prostate cancer, with dose escalation improving disease control. However, increasing radiation doses elevate the risk of rectal toxicity. Injectable absorbable gels provide a promising solution by physically separating the prostate and rectum. This study aims to evaluate a novel absorbable gel, designed to be both bioabsorbable and CT-visible, through preclinical animal studies assessing its dosimetric impact, safety, and CT imaging performance in prostate radiotherapy.Materials/Methods:
Beagle dogs (n=15) were randomized into three groups: Group A (gel injection + radiotherapy), Group B (radiotherapy alone), and Group C (gel injection alone). The gel was injected into the prostate-rectal space under transrectal ultrasound guidance. To assess its protective effect, all groups underwent MRI, CT imaging, and dose-volume histogram (DVH) analysis. Radiotherapy was delivered with a prescribed dose of 40 Gy in 5 fractions.The CT visibility of the gel was evaluated in SD rats, Dutch rabbits, and beagle dogs through serial imaging. scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analyses were performed to assess calcium-phosphate biomineralization.
Results:
Dosimetric and Safety Outcomes in Beagle Dogs MRI and CT imaging confirmed stable gel placement between the prostate and rectum, creating an average separation distance of 1.32 ± 0.28 cm (n=12). Gel volume remained within 7–9 mL in Group A and 5–8 mL in Group C, with gradual degradation over six months. DVH analysis revealed that rectal dose exposure at V15 and higher was significantly lower in Group A than in Group B (p < 0.01), with a maximum rectal dose reduction of 6.32 Gy (40.85 Gy vs. 47.17 Gy, p = 0.001). No significant differences in prostate or bladder dose distributions were observed between groups. Histopathological analysis showed that rectal mucosal injury was significantly mitigated in Group A compared to Group B, with fewer inflammatory infiltrates.CT Visibility Outcomes In SD rats and Dutch rabbits, CT imaging revealed progressive radiopacity around the gel, attributed to biomimetic mineralization. SEM and EDX confirmed calcium-phosphate deposition, with a Ca/P ratio of 1.59. Lowering the phosphate concentration in the gel eliminated CT visibility, supporting the in situ mineralization mechanism. However, this effect was not observed in beagle dogs, indicating potential species-specific differences requiring further investigation.
Conclusion:
The biomimetic mineralization radioprotective absorbable gel demonstrated high stability, predictable degradation kinetics, and safety in preclinical models. Additionally, CT self-visualization was successfully achieved in small animal models, highlighting its potential to enhance treatment planning accuracy. Further optimization is needed to ensure consistent CT visibility in larger animal models.