Top Line: How can we predict the risk of vertebral compression fracture (VCF) after spine SBRT?
The Study: Despite improved local control and pain control, VCF is a potential complication of spine SBRT. This retrospective cohort study from the Mayo system used data from 331 patients treated with spine SBRT to develop a model predictive of VCF. Most patients were treated with a single 16-24 Gy fraction (median 20 Gy) and ~30% had multifraction treatment (median 30 Gy). At a median follow-up of 21 months, the rate of VCF was 18%. Most of these (76%) were de novo fractures while the rest (24%) were progression of existing fractures. Median time to VCF was 9 months after SBRT. Nearly half of fractures (49%) were categorized as severe–resulting in >40% vertebral height loss. There were multiple patient (females), disease (kidney primary), radiographic (VB involvement or existing VCF), and treatment (BED10 > 60 Gy) factors significantly associated with VCF risk. However, the recursive partitioning analysis model identified the 4 most important predictors of VCF risk: GTV > 10cc, lumbar spine location, epidural tumor extension, and a SINS score >6. Those with a high risk score (total of 3-4) had a 35% risk of VCF compared to 17% for intermediate risk score (2) and 6.7% for those with a low risk score (0-1).
TBL: This 4 point model is a useful way to identify patients at high risk of VCF after spine SBRT who may benefit from additional stabilization procedures. | Kowalchuk, JAMA Oncol 2022