Top Line: Single-isocenter multi-target radiosurgery has become increasingly attractive as we treat patients with ever-growing numbers of brain metastases, but concerns about rotational error have traditionally driven the use of multiple isocenters and/or planning margins.
The Study: A retrospective series! of 429 patients harboring 3,039 intact brain metastases evaluated outcomes after frameless LINAC-based Single-isocenter multi-target radiosurgery delivered with a 0-mm PTV margin. This was paired with six-degrees-of-freedom couch corrections and intrafraction surface monitoring. The majority (70%) of lesions were located ≥4 cm from isocenter (median distance 4.9 cm). This is important because patients were treated using Varian HD-120 multileaf collimator, which employs 2.5-mm central leaves spanning 4 cm on either side of isocenter (8 cm total) and 5-mm peripheral leaves. Despite this, local control at one year was an impressive 95%. There was no difference between lesions <4 cm versus ≥4 cm from isocenter (94.1% vs 95.5%), and distance from isocenter was not associated with local failure on multivariable analysis. Grade 3+ adverse events remained uncommon at 2%.
TBL: These data suggest that carefully delivered zero-margin, single-isocenter multi-target radiosurgery can remain highly-accurate—even when treating lesions several centimeters from isocenter. | Moradi, Int J Radiat Oncol Biol Phys 2026
The Study: A retrospective series! of 429 patients harboring 3,039 intact brain metastases evaluated outcomes after frameless LINAC-based Single-isocenter multi-target radiosurgery delivered with a 0-mm PTV margin. This was paired with six-degrees-of-freedom couch corrections and intrafraction surface monitoring. The majority (70%) of lesions were located ≥4 cm from isocenter (median distance 4.9 cm). This is important because patients were treated using Varian HD-120 multileaf collimator, which employs 2.5-mm central leaves spanning 4 cm on either side of isocenter (8 cm total) and 5-mm peripheral leaves. Despite this, local control at one year was an impressive 95%. There was no difference between lesions <4 cm versus ≥4 cm from isocenter (94.1% vs 95.5%), and distance from isocenter was not associated with local failure on multivariable analysis. Grade 3+ adverse events remained uncommon at 2%.
TBL: These data suggest that carefully delivered zero-margin, single-isocenter multi-target radiosurgery can remain highly-accurate—even when treating lesions several centimeters from isocenter. | Moradi, Int J Radiat Oncol Biol Phys 2026