Top Line: What happens if you deviate from International Spine Radiosurgery Consortium guidelines for spine SBRT target volume delineation?
The Study: Multiple studies have shown that not covering adjacent compartments of the vertebra can lead to higher recurrence risk. However, there is limited head to head comparison of the elective approach and the GTV only approach. In this phase 2 trial, 106 patients with 164 involved spine segments planned to be treated with SBRT were randomized to elective field (EF) or involved field (IF) SBRT. EF followed the ISRC recommendations for covering the tumor plus adjacent uninvolved segments. In the IF arm, the target volume was the GTV plus an 8mm intraosseous margin. In both arms, the prescription dose was 16 Gy in 1 fraction. The primary endpoint of <10% failure at 6 months was met in both arms (3.8% EF v 7.5% IF). However, at 12 months failure was significantly lower with the standard EF approach on a per-patient (3.8% v 13.5%) and a per-segment basis (2.6% v 11.8%). Two-thirds of the failures in the IF arm would have fallen within the ISRC CTV.
TBL: Treating only the GTV plus a margin with spine SBRT significantly increases the risk of recurrence compared with an elective field approach as most failures occur in adjacent segments. | Chen, Neuro Oncol 2025
The Study: Multiple studies have shown that not covering adjacent compartments of the vertebra can lead to higher recurrence risk. However, there is limited head to head comparison of the elective approach and the GTV only approach. In this phase 2 trial, 106 patients with 164 involved spine segments planned to be treated with SBRT were randomized to elective field (EF) or involved field (IF) SBRT. EF followed the ISRC recommendations for covering the tumor plus adjacent uninvolved segments. In the IF arm, the target volume was the GTV plus an 8mm intraosseous margin. In both arms, the prescription dose was 16 Gy in 1 fraction. The primary endpoint of <10% failure at 6 months was met in both arms (3.8% EF v 7.5% IF). However, at 12 months failure was significantly lower with the standard EF approach on a per-patient (3.8% v 13.5%) and a per-segment basis (2.6% v 11.8%). Two-thirds of the failures in the IF arm would have fallen within the ISRC CTV.
TBL: Treating only the GTV plus a margin with spine SBRT significantly increases the risk of recurrence compared with an elective field approach as most failures occur in adjacent segments. | Chen, Neuro Oncol 2025