Gamma Knife radiosurgery as safe alternative to craniotomy for large brain metastases

A new treatment option has emerged for patients with large brain metastatic cancer exceeding 10 cubic centimeters in volume, for whom craniotomy was previously the primary recommendation.

This is thanks to a Korean research team demonstrating the efficacy of “fractionated Gamma Knife radiosurgery” as a primary treatment for safely and effectively treating large metastatic brain tumors.

Seoul National University Hospital announced on Wednesday that a research team led by Professors Paek Sun-ha and Myung Ho-sung of the hospital’s Department of Neurosurgery retrospectively analyzed the efficacy and safety of this surgical method in 93 patients who underwent fractionated Gamma Knife radiosurgery as primary treatment after diagnosis of large brain metastases.

The results showed tumor size reduction of up to 80 percent within nine months, and stabilization of neurological symptoms in 87 percent of patients.

Brain metastatic tumors develop when cancer cells from other organs spread to the brain. While radiosurgery is the primary treatment for small tumors, large brain metastases require rapid reduction of intracranial pressure by decreasing tumor volume, making craniotomy the first recommended option.

Recently, “fractionated radiosurgery” has gained attention as an alternative when craniotomy is difficult.

This approach has been reported to carry a lower risk of side effects compared to delivering a high dose of radiation in a single session and to effectively suppress tumor growth. However, the efficacy of fractionated radiosurgery as a primary treatment for large brain metastases has not yet been definitively established. Furthermore, research cases involving Gamma Knife-based therapy, which precisely delivers high-dose gamma rays only to the lesion, have been scarce.

The research team tracked recurrence, metastasis, and mortality after fractionated Gamma Knife radiosurgery. The median overall survival period was 15.2 months, similar to the previously reported survival periods (8-18 months) for craniotomy. The median progression-free survival period, defined as the time without recurrence or metastasis, was 8.2 months.

Additionally, the team assessed tumor and edema volume, neurological symptoms, and radiation toxicity at three-month intervals over two years. Results showed that eight out of 10 tumors decreased in volume by more than half, with a median time to maximum tumor volume reduction of 3.3 months.

The tumor and edema volumes continued to decrease steadily for six to nine months post-treatment, with a reduction of approximately 80 percent. Although temporary volume fluctuations occurred over a period of up to 18 months, volumes stabilized thereafter. These results suggest that fractionated Gamma Knife radiosurgery can reduce not only the tumor but also surrounding edema, thereby alleviating neurological symptoms. Indeed, neurological symptoms stabilized or improved within 6 months post-surgery in 87.1 percent of all patients.

Regarding safety, necrosis due to radiation toxicity occurred in 5.4 percent of patients, but none required hospitalization. The research team explained that fractionated Gamma Knife radiosurgery is a treatment that can achieve effective neurological improvement while avoiding complications associated with open surgery.

“This study is significant as it demonstrates the efficacy and safety of fractionated Gamma Knife radiosurgery for large brain metastases,” Professor Paek said. “Fractionated Gamma Knife radiosurgery can be recommended as a primary treatment alternative to surgical resection for large brain metastases.”