Radiation implant outperforms traditional radiation for brain metastases | ASCO 2026

Patients who had a bioabsorbable implant containing radiation “seeds” that was placed after brain metastasis surgery lived longer and were less likely to have their cancer grow back than patients who had received external beam radiation, according to late-breaking results presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, taking place May 29 to June 2 in Chicago.

Between 10% and 30% of all patients with cancer develop brain metastases, with between 100,000 and 200,000 new patients diagnosed each year. In these cases, patients undergo surgery to remove the brain tumor followed by external radiation. But this regimen often means that radiation can be delayed for some patients.

“We know that if radiation is not given within a four-week period of time, there’s an increased risk of local recurrence from 2.3% to close to 50%,” Jeffrey S. Weinberg, M.D., said in a press briefing before the meeting. “In addition, due to many logistical reasons, some patients never return to receive their SRT [stereotactic radiation], and frequently systemic therapy is held as we wait for the completion of the post-operative radiation.”

Weinberg is a professor of Neurosurgery and deputy Chair and Vice-Chair of Clinical Operations in The Department of Neurosurgery at The University of Texas, MD Anderson Cancer Center in Houston.

An alternative to external radiation is GammaTile, an FDA-cleared, bioabsorbable collagen implant embedded with radiation seeds that is designed for patients with operable brain tumors. Developed by GT Medical Technologies, GammaTile was launched in March 2020. The stamp-sized implant contains Cesium-131 radiation within what GT Medical Technologies calls seeds, and the entire implant is placed within the cavity where the tumor was. The collagen tile dissolves naturally over time, releasing the radiation.

Researchers in the MD Anderson Cancer Center study wanted to compare the use of the tile radiation to external radiation. “We hypothesized that the use of these tiles offers several logistical and possible biological advantages,” Weinberg said. “Radiation is initiated at the time of surgery. No additional procedures are required. Treatment compliance is ensured, and we believe that it may work better for larger cavities and can deliver a higher dose rate to the cavity surface.”

The phase 3 ROADS study, which was sponsored by GT Medical Technologies, enrolled 204 patients with a new brain metastasis that was 2 to 7 centimeters in diameter. Patients were enrolled between April 2021 and August 2025 at 32 centers.

The primary outcomes were time to surgical bed recurrence and surgical bed recurrence-free survival. Secondary outcomes consisted of overall survival, quality of life, and neurocognitive measurements, frequency of adverse events, and development of leptomeningeal disease (when cancer spreads to the cerebrospinal fluid) and radiation necrosis.

With a median follow-up time of 12.9 months, the study showed that tile-based radiation reduced the chances that brain metastases would grow back at the surgery site by 94%. In the control group of those who had received external radiation, 12% of people experienced surgical bed recurrence. In the tile group, that dropped to 1%.

In the control group, the median time to surgical bed recurrence was 17.4 months. But in the tile group, more than half the participants had no tumor-site growth. Median surgical bed recurrence-free survival was 10.9 months in the control group. In contrast, most people in the tile group were still alive without tumor regrowth, so a median had not been reached.

Tile-based radiation improved overall survival, with a 41% reduction in the risk of death. Researchers estimate that 61.7% of participants who received tile-based radiation will be alive 2 years after diagnosis, compared with 35.7% in the control group.

Serious adverse events were similarly common in the two groups, with grade 3 and higher adverse events occurring in 18.1% of the tile group and 19.3% of the control group. The occurrence of leptomeningeal disease and radiation necrosis did not differ significantly between the two groups.

Researchers will continue to study the data for more information, such as how the treatments affect mental processes like thinking, memory, and attention, as well as how other cancer therapies impact the effectiveness of these treatments. Additionally, a trial sponsored by GT Medical Technologies (BRIDGES) began enrollment in January 2026 and is assessing the tile-based radiation for the treatment of a glioblastoma, an aggressive type of brain cancer.