Cs-131 Collagen Tile Brachytherapy for Recurrent Glioblastoma: Treatment Outcomes and Toxicity

Recurrence in glioblastoma (GBM) is common, and the success of salvage strategies, including re-resection and reirradiation, is limited. Brachytherapy with Cs-131 collagen tiles enables intraoperative focal dose intensification with rapid dose fall-off and limited normal brain radiation exposure. We report the outcomes of Cs-131 collagen tile implantation at the time of resection for recurrent GBM.

We reviewed 15 adults with previously irradiated, recurrent isocitrate dehydrogenase (IDH) wild-type GBM who underwent maximal safe resection followed by intraoperative Cs-131 collagen tile implantation at a single institution. Candidates had surgically accessible, primarily enhancing recurrences ≥6 months after prior external beam radiation therapy, and were anticipated to have a gross total resection. The prescription dose was 60 Gy at a depth of 5 mm. We assessed overall survival, progression-free survival, toxicity, and patterns of failure (local ≤0.5 cm from the cavity, marginal 0.5-1 cm, and distant >1 cm) after implantation.

Patients (median age, 63 years; range, 39-76) had good performance status (median Karnofsky Performance Status score, 90; range, 70-100) and prior chemoradiation (most to 60 Gy/30 fractions). Tiles (median, 6.5/patient; range, 3-13) were implanted at first recurrence in 12 of 15 patients (80%) and at second recurrence in 3 (20%), at a median of 15 months after external beam radiation therapy (range, 8.9-47). At 13 months median follow-up (range, 1.4-21), the median overall survival after Cs-131 implantation was not reached (NR) (95% CI, 6.7-NR months); the median time to progression after Cs-131 implantation was 9 months (95% CI, 6.0-NR); and the cumulative incidence of first progression (local or distant) after Cs-131 implantation was 53.3% over the follow-up period. The first failures were local (n = 2), marginal (n = 2), distant (n = 3), and combined local and distant (n = 1). One patient developed symptomatic grade 3 radionecrosis, which improved with bevacizumab. No patients required reoperation for Cs-131 toxicity.

Intraoperative Cs-131 tile brachytherapy for recurrent GBM is feasible and well tolerated. Distant failures remain common. Integrating effective systemic therapy and careful patient selection may optimize outcomes.