Cesium-131 Tiles Placed at Resection Held Early Glioblastoma Regrowth to 6% in Phase I GESTALT Trial

Sixty-seven confirmed cases across 15 centers

Investigators planned for 61 patients, a number chosen so the feasibility rate could be estimated within 10 percentage points. Seventy were enrolled and taken to surgery over three years, and 67 had glioblastoma confirmed. Gross total resection was achieved in 66% of them, and only patients with IDH-wildtype disease entered the survival analysis. Sites included Barrow Neurological Institute, the University of Minnesota, Piedmont Healthcare and ECU Health Medical Center, with Clark C. Chen of Brown University as first author.

The four-week gap the design attacks

Standard treatment leaves a stretch after craniotomy in which no radiation is delivered while the wound heals. Chen described the consequence in the announcement:

Even after a successful surgery, microscopic glioblastoma cells remain in the brain. In 50 to 70 percent of patients, these cells grow quickly enough to become visible on MRI scans before standard radiation treatment can begin.

The ASCO abstract puts the same phenomenon at about 50% and ties it to worse survival, particularly in unmethylated tumors. Against that, 6.0% of GESTALT patients showed centrally reviewed rapid early progression, a comparison drawn entirely from published series because the trial carried no control arm.

MGMT and IDH went to central review

Both markers were read centrally, and the split was 28 methylated to 39 unmethylated. Median progression-free survival was 9.3 months in the unmethylated group and had not been reached in the methylated group. The 16.5-month median overall survival in unmethylated patients sits above the roughly 13 months the authors quote from BN007 for that population.

GT Medical Technologies funded the trial and opened BRIDGES

GammaTile is made by GT Medical Technologies of Tempe, Arizona, which sponsored the trial and is authorized to distribute the device in the United States for newly diagnosed and recurrent malignant intracranial neoplasms. Chen is a consultant to the company and a participating investigator. Chief medical officer Michael Garcia said the results "show what's possible when we stop giving residual cancer cells time to regrow between surgery and radiation." GT Medical has opened BRIDGES (NCT07195591), a randomized phase 3 in frontline newly diagnosed glioblastoma. Brown University Health and its Legorreta Cancer Center are a host institution for the APE|APO Event Series, the meetings behind this publication.

Why This Matters to the APO|APE Reader

BRIDGES will have to reproduce that 6.0% against a randomized control scored by the same central readers, and it inherits an ordering problem visible in the phase I numbers: three of the 70 patients taken to surgery did not have glioblastoma confirmed, and one of the 67 turned out IDH-mutant. Tiles go into the cavity on an intraoperative impression, before the neuropathology and central MGMT and IDH results return. Any center adopting the approach commits to a radiation decision made hours ahead of the molecular diagnosis the survival curves are later split on.