Purpose

Vertebral compression fracture (VCF) is a notable complication following spinal stereotactic body radiotherapy (SBRT). Previous studies have identified advanced Spinal Instability Neoplastic Score (SINS), endplate (EP) disruption, and adverse pathology as significant factors contributing to an increased risk of VCF. This study aims to expand the patient cohort to further explore the role of EP disruption in VCF development.

Methodology

This single-institution retrospective cohort study analyzed demographic and treatment data from patients who underwent spinal SBRT between 2013 and 2020. EP disruption was assessed using pre-SBRT CT scans. Chronic steroid use was defined as steroid administration for a duration of four weeks or longer. The 1-year cumulative incidence of VCF, was monitored through follow-up MRI and CT scans conducted at 3-month intervals post-treatment.

Results

168 patients were included in the analysis, with a median follow-up of 18.7 months. Most patients (87%) underwent multi-fraction radiation therapy with a median dose of 27 Gy and a biologically effective dose (BED10) of 51.3 Gy. VCF occurred in 18% of patients, with a median onset of 4.8 months. The SINS score indicated that 55% of patients had a score below 7, 31% had a score of 7, and 14% had a score above 7. The 1-year cumulative VCF incidence revealed several key findings: primary cancers from non-small cell lung cancer (NSCLC), breast, and ano-colorectal origins exhibited a higher VCF rate (27%) compared to other types (12%) (p< 0.001). Chronic steroid use was significantly associated with increased VCF incidence (38% vs. 13%, p=0.01). Patients with a SINS score above 7 experienced a higher VCF rate (32%) than those with a score below 7 (4%) (p< 0.001). Bilsky grade 1 lesions had a higher VCF rate (28%) compared to grade 0 lesions (11%) (p=0.001). Additionally, EP disruption was significantly associated with VCF risk (31% vs. 5%, p< 0.001). Univariate analysis revealed that chronic steroid use, higher SINS score, Bilsky grade 1, EP disruption, adverse pathology, and circumferential treatment were associated with increased VCF risk, with hazard ratios (HR) for steroid use (HR 2.87, p=0.02), SINS score (HR 1.62, p< 0.001), Bilsky grade 1 (HR 3.19, p=0.002), EP disruption (HR 6.02, p< 0.001), adverse pathology (HR 3.31, p=0.001), and circumferential treatment (HR 2.26, p=0.03). Multivariable analysis confirmed that chronic steroid use (HR 2.91, p=0.04), SINS score (HR 1.31, p=0.005), EP disruption (HR 3.42, p=0.016), and adverse pathology (HR 2.81, p=0.007) were independent predictors of VCF risk.

Conclusions

This expanded analysis reaffirms the association of EP disruption, adverse pathology, and higher SINS scores with an increased risk of VCF. Additionally, chronic steroid use for four weeks or longer was identified as a significant predictor of VCF risk.