Novel Radiation Strategy Redefines a New Treatment Paradigm for Glioblastoma

The findings were presented as a podium presentation at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting and provide the foundation for a planned Phase III randomized clinical trial.¹

Glioblastoma is an aggressive brain cancer that is difficult to treat. Standard treatment includes surgery to remove as much of the tumor as possible, followed by radiation and chemotherapy. However, to allow the brain and surgical incision time to heal following tumor removal, radiation and chemotherapy are typically delayed for three to six weeks after surgery. During this time, cancer cells left behind after surgery can continue to grow and multiply.

"Even after a successful surgery, microscopic glioblastoma cells remain in the brain," said Dr. Chen. "In 50 to 70 percent of patients, these cells grow quickly enough to become visible on MRI scans before standard radiation treatment can begin. In some cases, the tumor grows back to a size that requires a second surgery. This early regrowth is associated with poorer survival, creating an urgent need for treatments that can target cancer cells without affecting wound healing."

To address this challenge, investigators evaluated GammaTile® (GT Medical Technologies, Tempe, Arizona), a cesium-131-based radiation therapy implanted directly into the surgical cavity at the time of tumor removal. Unlike conventional external beam radiation therapy (EBRT) that requires waiting until the patient has healed from surgery, GammaTile® begins delivering radiation immediately after surgery. Because the radiation travels only a short distance, it remains concentrated around the area where the tumor was removed and does not interfere with wound healing. The treatment also delivers radiation doses that are two to four times higher than can be safely achieved with conventional external beam radiation therapy.

Dr. Chen led the Phase I GESTALT clinical trial (NCT05342883) involving 15 hospitals across the United States to determine whether GammaTile® could be safely incorporated into standard glioblastoma treatment. The study included 67 patients and found that the combined treatment, which comprised surgery and concurrent GammaTile® placement followed by a shortened course of EBRT and standard chemotherapy, was safe and practical to deliver. Patients who received GammaTile® did not experience more serious side effects than those typically seen with standard treatment alone.

Most notably, only 6 percent of patients experienced rapid early tumor regrowth after surgery, compared with the 50 to 70 percent rates commonly reported when patients must wait three to six weeks before starting radiation and chemotherapy.^2-3 The findings suggest that delivering radiation at the time of surgery may help prevent cancer growth during this critical period.

"These results suggest that immediate radiation treatment at the time of surgery may address one of the most significant challenges in glioblastoma care," said Dr. Chen. "By treating residual cancer cells during the recovery period, we may be able to reduce early tumor regrowth while maintaining the safety of standard treatment."

"GammaTile was built to close the gap in glioblastoma care created by the wait for traditional external beam radiation to begin after surgery," said Michael Garcia, M.D., M.S., Chief Medical Officer of GT Medical Technologies. "These results show what's possible when we stop giving residual cancer cells time to regrow between surgery and radiation. We're grateful to Dr. Chen and the entire GESTALT investigator team for the rigor they brought to this trial, and we're energized to support the Phase III study that will build on it. Based on these findings, a Phase III randomized clinical trial, BRIDGES (NCT07195591), has been launched to further evaluate the potential benefits of incorporating GammaTile® into the frontline treatment of newly diagnosed glioblastoma."

"GT Medical Technologies was founded by brain tumor specialists who believed that innovative radiation therapy approaches were critical for improving patient outcomes," said Per Langoe, Chief Executive Officer of GT Medical Technologies. "These trial results suggest that we are realizing their vision for patients with glioblastoma, and the ongoing Phase III BRIDGES trial will further inform our understanding of how GammaTile may improve patient outcomes."

This study was sponsored by GT Medical Technologies, Inc. Dr. Chen is a consultant for GT Medical and a participating investigator in the NCT05342883 trial.

References:

1. Chen C, et al. Presented at: American Society of Clinical Oncology; May 31, 2026; Chicago, IL.
2. Waqar M, et al. Neuro-oncology Adv. 4 (2022).
3. Guzzino J, et al. J Neurooncol. 176:5 (2025). 

About GT Medical Technologies, Inc.

GT Medical Technologies was founded by a dedicated team of tumor specialists to address unmet needs in brain tumor treatment. The Company is committed to improving the lives of patients with brain tumors through innovative solutions that elevate the standard of care. GammaTile is authorized for commercial distribution in the United States as a treatment for patients with newly diagnosed malignant intracranial neoplasms and patients with recurrent intracranial neoplasms.

About Brown University Health:

Formed in 1994, Brown University Health is a not-for-profit health system based in Providence, R.I. comprised of three teaching hospitals of The Warren Alpert Medical School of Brown University: Rhode Island Hospital and its Hasbro Children's Hospital; The Miriam Hospital; and Bradley Hospital, the nation's first psychiatric hospital for children. The system also includes Newport Hospital, Saint Anne's Hospital, and Morton Hospital, offering a broad range of health services; Gateway Healthcare, the state's largest provider of community behavioral health care; Brown Health Medical Group, the largest multi-specialty practice in Rhode Island; and Brown Health Medical Group Primary Care, a primary care-driven medical practice. Brown University Health teaching hospitals are among the country's top recipients of research funding from the National Institutes of Health. The hospitals received over $145 million in external research funding in fiscal 2023. All Brown University Health-affiliated partners are charitable organizations that depend on community support to provide programs and services.

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SOURCE GT Medical Technologies