Dividing radiosurgery treatments may improve brain tumour outcomes, study suggests

Fractionated radiosurgery could offer a more effective way to treat large brain metastases after surgery, reducing the risk of recurrence and extending survival compared with a single treatment, a randomised trial has found.

The randomised trial involved 242 patients with one to four brain metastases, including at least one tumour larger than two centimetres that had been surgically removed.

After one year, 87 per cent of patients receiving fractionated treatment had no recurrence at the surgical site, compared with 81 per cent receiving a single treatment.

Paul D. Brown, radiation oncologist at Mayo Clinic Comprehensive Cancer Center and co-principal investigator of the study, said: “The study findings give us the evidence necessary to transform clinical practice. We can now offer patients a treatment that controls their disease and is associated with improved survival.”

Brain metastases are cancerous tumours that have spread to the brain from another part of the body. Radiation therapy is a standard treatment after surgery, but researchers said around 30 to 40 per cent of patients experience recurrence at the surgical site despite single-treatment radiosurgery.

Stereotactic radiosurgery uses three-dimensional imaging to deliver high doses of radiation precisely while limiting exposure to surrounding healthy brain tissue.

Patients were randomly assigned to either one treatment of stereotactic radiosurgery or fractionated treatment delivered over three or five treatments. Radiation doses were based on the size of the treatment area.

Brain metastases that had not been surgically removed were treated according to the same assigned schedule.

Researchers followed participants for a median of four years.

Median overall survival was 29 months among patients receiving fractionated radiosurgery, compared with 20 months for those receiving a single treatment.

Fractionated treatment was associated with a 31 per cent lower risk of death. Researchers found no difference in side effects or complications between the two approaches.

Fractionated radiosurgery also provided better control of brain metastases that had not been surgically removed, although this result was not statistically significant.

Dividing radiation across several treatments allows clinicians to deliver a higher total dose. It also gives healthy tissue time to recover between treatments, while tumour cells do not have the same ability to repair.

Brown said: “We see high recurrence rates in patients with brain metastases because the challenge is eliminating microscopic cancer cells left behind after surgery without exposing too much healthy brain tissue to high doses of radiation.”

The survival finding was unexpected and the reason for the association remains unclear.

Brown said: “The survival benefit was an unexpected finding, and while the exact mechanism remains unclear, we suspect that advances in systemic therapies over the past decade may be interacting with better control of disease within the brain, and overall, better outcomes for patients.”

Robert Mutter, chair of research in the Department of Radiation Oncology and co-leader of the Novel Therapeutics and Therapeutic Modalities Research Program at Mayo Clinic Comprehensive Cancer Center, said: “This is a practice-changing clinical trial in our field, demonstrating that fractionated radiosurgery not only reduces recurrence after surgery for large brain metastases but may also improve overall survival.”