International journal of radiation oncology, biology, physics 2016-10-01
Stereotactic Radiosurgery for Brainstem Metastases: An International Cooperative Study to Define Response and Toxicity.
Abstract
Purpose
To pool data across multiple institutions internationally and report on the cumulative experience of brainstem stereotactic radiosurgery (SRS).
Methods and materials
Data on patients with brainstem metastases treated with SRS were collected through the International Gamma Knife Research Foundation. Clinical, radiographic, and dosimetric characteristics were compared for factors prognostic for local control (LC) and overall survival (OS) using univariate and multivariate analyses.
Results
Of 547 patients with 596 brainstem metastases treated with SRS, treatment of 7.4% of tumors resulted in severe SRS-induced toxicity (grade ≥3, increased odds with increasing tumor volume, margin dose, and whole-brain irradiation). Local control at 12 months after SRS was 81.8% and was improved with increasing margin dose and maximum dose. Overall survival at 12 months after SRS was 32.7% and impacted by age, gender, number of metastases, tumor histology, and performance score.
Conclusions
Our study provides additional evidence that SRS has become an option for patients with brainstem metastases, with an excellent benefit-to-risk ratio in the hands of experienced clinicians. Prior whole-brain irradiation increases the risk of severe toxicity in brainstem metastasis patients undergoing SRS.
Related Questions
How do you approach SRS to a thalamic metastasis?
I am not aware of high-quality data to guide us here, but there is abundant published retrospective experience. A model by Flickinger et al. predicted higher toxicity rates after SRS in AVM patients for brainstem and other deep locations. That said, low toxicity has been reported for treatment of AV...
What dose/fractionation would you recommend for a large brainstem metastasis?
This is always a difficult clinical decision; for "large" (however one chooses to define this) pontine/medullary/brainstem mets, most have moved away from single fraction SRS to 3 fraction SRS (27 Gy in 9 fractions), based largely on the results of the Italian trial. In this trial, 289 patients with...
What is the optimal schedule for fractionated SRS treatment of CNS tumors?
I don't think there is one ideal dose/fraction schedule. Doses should be individualized for your institution, including factors such as immobilization, set up, and margins. There are published data on ranges of SRT.For larger tumors, typically defined as 2 cm to up to 3-4 cm I would favor 24-27 Gy i...
What is the best way to treat a small brainstem met with stereotactic radiosurgery?
Small brain metastases in the brainstem can be treated with radiosurgery safely. Typically, the dose is dialed down to minimize the risk of radiation necrosis within the brainstem. At our institution, we typically reduce the dose down by one dose level using the RTOG scheme. For example, a 2 cm or l...