ASTRO 2026 | Study Shows Fractionated Radiosurgery Improves Local Control in Post-Surgery Treatment for Large Brain Metastases

Research presented at the American Society for Radiation Oncology (ASTRO) Annual Meeting highlights the benefits of fractionated stereotactic radiosurgery over single-session treatment in reducing the recurrence of large brain metastases at the surgical site. According to the results of a phase 3 clinical trial, delivering radiation therapy in three to five sessions post-surgery significantly decreased cancer recurrence rates compared with a single-session approach. The trial, conducted by Mayo Clinic and others, demonstrates the potential for fractionated treatment to enhance patient outcomes without increasing adverse effects.

Brain metastases, which occur when cancer cells spread to the brain, are diagnosed in an estimated 200,000 individuals annually in the United States. Surgical intervention is often necessary when these metastases cause pressure or other symptoms like seizures or headaches. However, post-surgical recurrence remains a challenge due to the potential for residual microscopic cancer cells.

The multicenter trial, referred to as Alliance A071801, involved 242 patients with one to four brain metastases, including at least one over 2 centimeters that had been surgically removed. Participants were randomly assigned to receive either a single session of radiosurgery or fractionated treatments over three to five sessions. Follow-up periods extending to a median of four years focused on recurrence rates and overall survival.

Findings indicate that 87% of patients treated with fractionated radiosurgery remained free from surgical site recurrence one year after treatment, compared to 81% of those who received a single session. Although fractionated radiosurgery showed a trend towards better control of non-surgically removed metastases, this difference was not statistically significant.

Principal investigator Dr. Paul D. Brown from the Mayo Clinic explained the trial's rationale: "Dividing the radiation dose allows healthy tissue time to recover, enhancing the delivery of an effective dose to the treatment area while improving local control." Corresponding author Dr. Ayal A. Aizer of Mass General Brigham/Dana-Farber Cancer Institute added, "The study provides compelling evidence that fractionating radiosurgery should be a standard postoperative approach."

Median overall survival improved for the fractionated group, recorded at 29 months versus 20 months for the single-session group. Despite the unexpected survival benefit being unexplainable within the study's framework, researchers highlight the significance of maintaining disease control in the brain for improved long-term outcomes.

Commenting on the study, Dr. Lia Halasz from the Fred Hutch Cancer Center emphasized it provides robust randomized evidence in favor of fractionated approaches. As the radiation oncology community continues to seek optimal post-surgical treatments, fractionated radiosurgery stands out as a promising method to improve local control and potentially extend survival for patients with large brain metastases.