Development and Assessment of a Predictive Score for Vertebral Compression Fracture After Stereotactic Body Radiation Therapy for Spinal Metastases.

IMPORTANCE: Vertebral compression fracture (VCF) is a potential adverse effect following treatment with stereotactic body radiation therapy (SBRT) for spinal metastases. OBJECTIVE: To develop and assess a risk stratification model for VCF after SBRT. DESIGN, SETTING, AND PARTICIPANTS: This retrospective cohort study conducted at a high-volume referral center included 331 patients who had undergone 464 spine SBRT treatments from December 2007 through October 2019. Data analysis was conducted from November 1, 2020, to August 17, 2021. Exclusions included proton therapy, prior surgical intervention, vertebroplasty, or missing data. EXPOSURES: One and 3 fraction spine SBRT treatments were most commonly delivered. Single-fraction treatments generally involved prescribed doses of 16 to 24 Gy (median, 20 Gy; range, 16-30 Gy) to gross disease compared with multifraction treatment that delivered a median of 30 Gy (range, 21-50 Gy). MAIN OUTCOMES AND MEASURES: The VCF and radiography components of the spinal instability neoplastic score were determined by a radiologist. Recursive partitioning analysis was conducted using separate training (70%), internal validation (15%), and test (15%) sets. The log-rank test was the criterion for node splitting. RESULTS: Of the 331 participants, 88 were women (27%), and the mean (IQR) age was 63 (59-72) years. With a median follow-up of 21 months (IQR, 11-39 months), we identified 84 VCFs (18%), including 65 (77%) de novo and 19 (23%) progressive fractures. There was a median of 9 months (IQR, 3-21 months) to developing a VCF. From 15 candidate variables, 6 were identified using the backward selection method, feature importance testing, and a correlation heatmap. Four were selected via recursive partitioning analysis: epidural tumor extension, lumbar location, gross tumor volume of more than 10 cc, and a spinal instability neoplastic score of more than 6. One point was assigned to each variable, and the resulting multivariable Cox model had a concordance of 0.760. The hazard ratio per 1-point increase for VCF was 1.93 (95% CI, 1.62-2.30; P < .001). The cumulative incidence of VCF at 2 years (with death as a competing risk) was 6.7% (95% CI, 4.2%-10.7%) for low-risk (score, 0-1; 273 [58.3%]), 17.0% (95% CI, 10.8%-26.7%) for intermediate-risk (score, 2; 99 [21.3%]), and 35.4% (95% CI, 26.7%-46.9%) for high-risk cases (score, 3-4; 92 [19.8%]) (P < .001). Similar results were observed for freedom from VCF using stratification. CONCLUSIONS AND RELEVANCE: The results of this cohort study identify a subgroup of patients with high risk for VCF following treatment with SBRT who may potentially benefit from undergoing prophylactic spinal stabilization or vertebroplasty.

The value of routine biopsy during percutaneous kyphoplasty for vertebral compression fractures.

OBJECTIVE: Percutaneous kyphoplasty (PKP) is now widely performed to treat VCF, which is usually caused by osteoporosis. Previous researches have reported unsuspected malignancies found by biopsy. However, the safety and cost-effective profiles of routine biopsy during PKP are unclear. The purpose of this study was to evaluate the feasibility of routine biopsy during PKP in treatment of VCF. METHODS: Ninety-three patients (September 2007-November 2010) undergoing PKP without biopsy were reviewed as the control group. One hundred and three consecutive patients (November 2010-September 2013) undergoing PKP with biopsy of every operated vertebral level were prospectively enrolled as the biopsy group. The rate of unsuspected lesions was reported, and the severe adverse events, surgical duration, cement leakage rate and pain control were compared between the two groups. RESULTS: No statistically significant differences were found between the two groups, regarding the severe adverse events, surgical duration, cement leakage rate and pain control. Four unsuspected lesions were found in the biopsy group, three of which were malignancies with a 2.9% (3/103) unsuspected malignancy rate. The economic analysis showed that routine biopsy was cost-effective in finding new malignancies comparing with a routine cancer screening campaign. CONCLUSIONS: Routine biopsy during PKP was safe and cost-effective in finding unsuspected malignancies. We advocate routine biopsy in every operated vertebral level during PKP for VCF patients.

Metastatic burst fracture risk assessment based on complex loading of the thoracic spine.

The mechanical integrity of vertebral bone is compromised when metastatic cancer cells migrate to the spine, rendering it susceptible to burst fracture under physiologic loading. Risk of burst fracture has been shown to be dependent on the magnitude of the applied load, however limited work has been conducted to determine the effect of load type on the stability of the metastatic spine. The objective of this study was to use biphasic finite element modeling to evaluate the effect of multiple loading conditions on a metastatically-involved thoracic spinal motion segment. Fifteen loading scenarios were analyzed, including axial compression, flexion, extension, lateral bending, torsion, and combined loads. Additional analyses were conducted to assess the impact of the ribcage on the stability of the thoracic spine. Results demonstrate that axial loading is the predominant load type leading to increased risk of burst fracture initiation, while rotational loading led to only moderate increases in risk. Inclusion of the ribcage was found to reduce the potential for burst fracture by 27%. These findings are important in developing a more comprehensive understanding of burst fracture mechanics and in directing future modeling efforts. The results in this study may also be useful in advising less harmful activities for patients affected by lytic spinal metastases.

Vertebroplasty in osteoporotic spine fractures: a quality of life assessment.

OBJECTIVE: Our goal was to perform a quantitative evaluation of the improvement in functional capacity, quality of life, mental function, reduction in drug intake and impact on hospital admissions after vertebroplasty in the treatment of osteoporotic compression fractures. The efficacy of vertebroplasty in relief of pain has been addressed in previous publications but the quantitative evaluation of improvement in quality of life has not been addressed before. METHODS: This is a prospective study of 42 patients with 83 symptomatic vertebral fractures treated by vertebroplasty with a mean follow-up of 9.1 months. The outcome was measured by pre and postoperatively utilizing the Visual Analogue Scale, the Oswestry Disability Index, the Rolland Morris Scale for Back Pain and EuroQol-5D questionnaire (EQ-5D). The postoperative evaluations were performed at one week, one month, three month, and six month intervals thereafter. RESULTS: In 34 out of 39 active patients, marked pain relief was noted (87%). The Visual Analogue Scale score improved from a mean preoperative score of 8.2 to a mean postoperative score of 2.9 (p=0.0000003) at one week follow up and 3.9 at the last follow-up. The Rolland Morris Scale for Back Pain showed a drop from a mean preoperative rating of 13 to a mean postoperative rating of 10, showing a 25% improvement (p= 0.0207). The Oswestry Disability Index preoperatively was 64.4 which improved to 43.8 postoperatively, showing a 32% improvement (p= 0.0207). The EQ-5D showed a mean preoperative index value of 0.097 and mean postoperative index value of 0.592 (p = 0.0000003). All p-values were determined by the Willcoxin sign-ranked test. CONCLUSION: Vertebroplasty is a safe and efficacious procedure with a resulting improvement in pain and quality of life.