Top Line: How to target margins impact the risk of recurrence and toxicity following radiosurgery for brain metastases?
The Study: The use of expanded margins around brain metastasis radiosurgery targets is highly variable. This systematic review and meta-analysis analyzed data from 17 studies that included over 5000 lesions treated with SRS. The majority of lesions (73.5%) were treated with a margin and the rest were treated with no margin. Among those treated with a margin, the median was 1.5mm (ranging from 1mm to 3mm). A big challenge in comparing SRS studies is the variation in prescribing methods. In this meta-analysis, all patients treated with no margin received single fraction SRS with a median prescription dose of 21 Gy. Among those treated with single fraction SRS with a margin, the median prescription dose was 19.5 Gy. There was no significant difference in local control at 1 year with or without a margin (88.4% v 83%). There was also no significant difference in the pooled rate of radiographic radionecrosis with or without a margin (7% v 9.2%), and this held true when comparing only those treated with single fraction SRS. The rate of symptomatic radionecrosis was also similar with or without a margin (4.1% v 8.6%). It seems this study could be used to support either side of the margin debate. Using PTV margins doesn’t seem to increase toxicity but it also doesn’t improve local control. Using no margin doesn’t increase recurrence risk but it also doesn’t seem to reduce necrosis risk.
TBL: This systematic review and meta-analysis found no differences in the risks of radionecrosis and local recurrence in brain metastases treated with or without a PTV margin. | Singh, Pract Radiat Oncol 2025
The Study: The use of expanded margins around brain metastasis radiosurgery targets is highly variable. This systematic review and meta-analysis analyzed data from 17 studies that included over 5000 lesions treated with SRS. The majority of lesions (73.5%) were treated with a margin and the rest were treated with no margin. Among those treated with a margin, the median was 1.5mm (ranging from 1mm to 3mm). A big challenge in comparing SRS studies is the variation in prescribing methods. In this meta-analysis, all patients treated with no margin received single fraction SRS with a median prescription dose of 21 Gy. Among those treated with single fraction SRS with a margin, the median prescription dose was 19.5 Gy. There was no significant difference in local control at 1 year with or without a margin (88.4% v 83%). There was also no significant difference in the pooled rate of radiographic radionecrosis with or without a margin (7% v 9.2%), and this held true when comparing only those treated with single fraction SRS. The rate of symptomatic radionecrosis was also similar with or without a margin (4.1% v 8.6%). It seems this study could be used to support either side of the margin debate. Using PTV margins doesn’t seem to increase toxicity but it also doesn’t improve local control. Using no margin doesn’t increase recurrence risk but it also doesn’t seem to reduce necrosis risk.
TBL: This systematic review and meta-analysis found no differences in the risks of radionecrosis and local recurrence in brain metastases treated with or without a PTV margin. | Singh, Pract Radiat Oncol 2025