Spine SBRT in Geriatric Patients: Implications of Age and Dose on Iatrogenic Vertebral Compression Fracture Risk.

Purpose: Stereotactic body radiotherapy (SBRT) is an effective treatment for spinal metastases, however, outcomes specific to a geriatric population have not been described. This study aims to investigate the efficacy and safety of spine SBRT, in particular the rate of iatrogenic vertebral compression fracture (VCF), in patients aged 70 and older.

Patients and methods: From a prospectively maintained single-institutional database of 976 patients and 2407 spinal segments treated with SBRT for vertebral metastases between 2008-2021, all patients aged 70 or above were retrospectively reviewed. The primary outcome is the risk of VCF. Secondary outcomes including MRI-based local failure and overall survival (OS).

Results: 252 consecutive patients with 580 spinal segments treated with spine SBRT were reviewed. The median age was 75.8 (range: 70-90.3) years and the median (interquartile range) follow-up duration was 16.9 (6.4-41.3) months. The median OS of the entire cohort was 20.3 months and the 2-year LF rate was 14.3%. The cumulative risk of VCF at 12 and 24 months were 8.4% and 12.3%, respectively. Significant predictors of VCF on multivariable analyses included greater biologically equivalent dose, baseline fracture and increasing age. In particular, the 2-year VCF rate and median time to VCF were 30.3% and 3.4 months for those 86 and older, compared to 11.2% and 12.8 months for those younger than 86, respectively (p=0.0011).

Conclusion and relevance: Spine SBRT should be considered in a geriatric population, however, for those 86 and older we suggest caution due to the significant risk of VCF.