Stereotactic Body Radiosurgery Associated With Rectal Displacement using Gelfoam for Sacral Chordomas: Preliminary Report of 3 Cases.

Purpose: The treatment of sacral chordomas remains challenging because of high recurrence rates, postoperative complications, and limited effective radiation therapy options. We report a small case series of sacral chordoma treated exclusively with photon-based stereotactic body radiation therapy (SBRT), incorporating rectal displacement via tomography-guided radiointerventional interposition of a Gelfoam-based solution. This novel combination has not been previously described in the literature. Methods and Materials: Patients with biopsy-confirmed sacral conventional chordomas were included. All patients underwent SBRT with rectal displacement, receiving a single 24-Gy fraction. Treatment parameters and planning details are outlined. Results: Between 2022 and 2024, 3 patients were analyzed. Two were treatment-naïve, whereas 1 had recurrent disease. The median age was 62 years (range, 57-70). After a median follow-up of 21 months (range, 3-32), the local control rate was 100%; there were no treatment-related clinically significant adverse events (including gastrointestinal/rectal toxicities), except for 1 patient who experienced transient pain. The average dose-gradient of 1.4 Gy/mm toward the rectum because of displacement, leading to a potential reduction of the rectal dose by approximately 7 to 14 Gy. Conclusions: This small case series suggests that SBRT with rectal using a Gelfoam-based solution is a feasible and well-tolerated approach for sacral chordoma treatment. Further prospective studies with larger cohorts and extended follow-up are warranted to validate these findings and assess long-term efficacy and safety.