Fringe treatment.

When using single-iso, multi-target (SIMT) SRS for multiple brain metastases, a practical concern is whether there is an increased risk of geographic miss for targets distant from the isocenter. The rationale is that the magnitude of positional inaccuracy is greater the farther you are from isocenter. In this retrospective study, local control for 140 patients treated with SIMT SRS for 708 mets was compared to 175 patients treated with single-iso, single-target SRS f or 379 mets. All patients were treated on the same LINAC-based SRS platform, and a 1 mm PTV margin was used. Lesions under 2.5 cm were treated with single fraction SRS while larger lesions received fractionated SRS. There was no difference in the rate of local recurrence between groups at 1 and 2 years. Distance from isocenter was also not associated with an increased risk of local recurrence. | Kraft, Radiother Oncol 2021