Purpose

Vertebral compression fractures (VCF) are a common and severe complication of spine stereotactic body radiation therapy (SBRT). We sought to analyze how volumetric dosimetry and clinical factors were associated with the risk of VCF.

Methods and Materials

We evaluated 173 spinal segments that underwent single fraction SBRT in 85 patients from a retrospective database. Vertebral bodies were contoured and dosimetric values were calculated. Competing risk models were used to evaluate the effect of clinical and dosimetry variables on the risk of VCF.

Results

Our primary endpoint was development of a post-SBRT VCF. New or progressive fractures were noted in 21/173 vertebrae (12.1%); the median time to fracture was 322 days. Median follow-up time was 426 days. Upon multivariable analysis, the percentages of vertebral body volume receiving >20 Gy and >24 Gy were significantly associated with increased risk of VCF (hazard ratio, 1.036, 1.104; P = .029, .044, respectively). No other patient or treatment factors were found to be significant on multivariable analysis. Sensitivity analysis revealed that the percentages of vertebral body volume receiving >20 Gy and >24 Gy required to obtain 90% sensitivity for predicting vertebral body fracture were 24% and 0%, respectively.

Conclusions

VCF is a common complication after SBRT, with a crude incidence of 12.1%. Treatment plans that permit higher volumes receiving doses >20 Gy and >24 Gy to the vertebral body are associated with increased risk of VCF. To achieve 90% sensitivity for predicting VCF post-SBRT, the percentage of vertebral volume receiving >20 Gy should be <24% and maximum point dose should be <24 Gy. These results may help guide clinicians when evaluating spine SBRT treatment plans to minimize the risk of developing posttreatment VCF.

中文翻译：

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单次脊柱立体定向放射治疗后椎体骨折风险的体积剂量学分析

目的

椎体压缩性骨折 (VCF) 是脊柱立体定向放射治疗 (SBRT) 的常见且严重的并发症。我们试图分析体积剂量测定和临床因素如何与 VCF 风险相关。

方法和材料

我们从回顾性数据库中评估了 85 名患者中接受单次 SBRT 的 173 个脊柱节段。对椎体进行轮廓绘制并计算剂量学值。使用竞争风险模型来评估临床和剂量学变量对 VCF 风险的影响。

结果

我们的主要终点是 SBRT 后 VCF 的开发。21/173 椎骨（12.1%）发现新的或进行性骨折；骨折的中位时间为 322 天。中位随访时间为 426 天。根据多变量分析，接受>20 Gy 和>24 Gy 的椎体体积百分比与 VCF 风险增加显着相关（风险比 分别为 1.036、1.104 ；P = .029、0.044）。在多变量分析中没有发现其他患者或治疗因素是显着的。敏感性分析显示，获得 90% 的预测椎体骨折敏感性所需的接受 >20 Gy 和 >24 Gy 的椎体体积百分比分别为 24% 和 0%。

结论

VCF是SBRT后常见的并发症，粗发生率为12.1%。允许接受更大体积的椎体剂量 >20 Gy 和 >24 Gy 的治疗计划与 VCF 风险增加有关。为了使预测 SBRT 后 VCF 的灵敏度达到 90%，接受>20 Gy 的椎体体积百分比应<24%，最大点剂量应<24 Gy。这些结果可能有助于指导临床医生评估脊柱 SBRT 治疗计划，以最大限度地降低发生治疗后 VCF 的风险。