GammaTile Placement at Surgery Cuts Early Tumor Regrowth in Glioblastoma

GT Medical Technologies announced new data from GESTALT, a phase 1 feasibility trial testing whether GammaTile, a radiation-emitting implant, can be safely incorporated into standard treatment for newly diagnosed glioblastoma (GBM). The findings, presented by principal investigator Clark Chen, MD, PhD, professor and director of the Brain Tumor Program at Brown University Health, were shared in a podium presentation at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting.¹

Why timing matters in GBM

Standard GBM treatment involves surgical resection followed by external beam radiation therapy (EBRT) and chemotherapy, but radiation is typically delayed 3 to 6 weeks after surgery to allow the brain and incision to heal. During that gap, residual microscopic tumor cells can continue proliferating; prior research has found that 50% to 70% of patients experience radiographic tumor regrowth, known as rapid early progression, before EBRT can begin, an outcome associated with worse survival and sometimes a second surgery.^1-3

Trial design

GESTALT (NCT05342883) enrolled 67 patients with newly diagnosed GBM across 15 US hospitals, including Tampa General Hospital and St. Louis University Hospital, in a single-arm design without a comparator group.^1,4 Patients underwent surgical resection with concurrent GammaTile placement in the resection cavity, followed by a shortened course of EBRT and the standard temozolomide-based chemotherapy regimen. The trial's primary goal was to determine whether this combined approach was safe and practical to deliver, rather than to formally test efficacy against a control arm.

Results

Overall, only 6% of GESTALT patients experienced rapid early progression, compared with the 50% to 70% historical rates cited above. In addition, patients receiving GammaTile did not experience more serious side effects than those typically associated with standard treatment alone, and the combined regimen was found to be practical to deliver across the multi-site cohort.¹

“Even after a successful surgery, microscopic glioblastoma cells remain in the brain,” Chen said in a statement.¹ “In 50 to 70 percent of patients, these cells grow quickly enough to become visible on MRI scans before standard radiation treatment can begin...This early regrowth is associated with poorer survival, creating an urgent need for treatments that can target cancer cells without affecting wound healing.” He added that the results “suggest that immediate radiation treatment at the time of surgery may address one of the most significant challenges in glioblastoma care.”¹

About GammaTile

GammaTile consists of cesium-131 radiation sources embedded in a bioresorbable collagen tile, placed directly into the surgical cavity at the time of tumor removal. Because the radiation travels only a short distance from the implant, it stays concentrated around the resection site without interfering with wound healing, and can deliver doses 2 to 4 times higher than what can safely be achieved with conventional EBRT.

The FDA first cleared GammaTile in 2018 for recurrent brain tumors and expanded that clearance in 2020 to include upfront treatment of any malignant brain tumor; more than 1,000 patients have been treated with the device to date.⁵

What's next

Based on the GESTALT findings, GT Medical Technologies has launched BRIDGES (NCT07195591), a phase 3, randomized, open-label trial comparing standard resection plus EBRT and temozolomide against resection with GammaTile placement followed by abbreviated EBRT and the same chemotherapy regimen, in patients with newly diagnosed GBM.⁶

“GammaTile was built to close the gap in glioblastoma care created by the wait for traditional external beam radiation to begin after surgery," Michael Garcia, MD, MS, chief medical officer of GT Medical Technologies, said in a statement.¹ "These results show what's possible when we stop giving residual cancer cells time to regrow between surgery and radiation.” Per Langoe, chief executive officer of GT Medical Technologies, added that the GESTALT results suggest the company is "realizing" its founders' vision for glioblastoma patients, and that the ongoing BRIDGES trial “will further inform our understanding of how GammaTile may improve patient outcomes.”

REFERENCES
1. Novel Radiation Strategy Redefines a New Treatment Paradigm for Glioblastoma. News release. GT Medical Technologies, Inc. August 18, 2026. Accessed August 25, 2026. https://www.prnewswire.com/news-releases/novel-radiation-strategy-redefines-a-new-treatment-paradigm-for-glioblastoma-302854200.html
2. Waqar M, Roncaroli F, Lehrer EJ, et al. Rapid early progression (REP) of glioblastoma is an independent negative prognostic factor: results from a systematic review and meta-analysis. Neurooncol Adv. 2022;4(1):vdac075. doi:10.1093/noajnl/vdac075
3. Guzzino J, et al. J Neurooncol. 2025;176(5).
4. Pilot Study of Resection and GammaTile Followed by Concomitant External Beam Radiation Therapy (EBRT) and Temozolomide (TMZ) and Adjuvant in Newly Diagnosed Glioblastoma (GBM). ClinicalTrials.gov identifier: NCT05342883. Accessed August 25, 2026. https://clinicaltrials.gov/study/NCT05342883
5. Grabowski MM, Recinos PF, Nowacki AS, et al. The role of GammaTile in the treatment of brain tumors: a technical and clinical overview. Front Neurol. Accessed August 25, 2026. https://pmc.ncbi.nlm.nih.gov/articles/PMC10834587/
6. BRIDGES: A Study of GammaTile Compared to Standard of Care in Newly Diagnosed Glioblastoma. ClinicalTrials.gov identifier: NCT07195591. Accessed August 25, 2026. https://clinicaltrials.gov/study/NCT07195591