JRSBRT 3.4, p. 297-305

Risk of vertebral compression fracture specific to osteolytic renal cell carcinoma spinal metastases after stereotactic body radiotherapy: A multi-institutional study
Isabelle Thibault, Eshetu G Atenafu, Eric Chang, Sam Chao, Ameen Al-Omair, Stephanie Zhou, Nicholas Boehling, Ehsan H. Balagamwala, Marcelo Cunha, John Cho, Lilyana Angelov, Paul D. Brown, John Suh, Laurence D. Rhines, Michael G. Fehlings and Arjun Sahgal

Purpose: Determine the risk of vertebral compression fracture (VCF) following stereotactic body radiotherapy (SBRT), specific to osteolytic renal cell carcinoma (RCC) spinal metastases, and associated predictive factors.

Methods: 187 RCC osteolytic spinal tumor segments in 116 patients obtained from a multi-institutional pooled database were reviewed. Each segment was evaluated according to the Spinal Instability Neoplastic Score (SINS).

Results: The median follow-up was 8.0 months. 34 VCF (34/187, 18%) were observed and median time to VCF was 2.4 months. VCF was observed in 43% (10/23), 24% (4/17) and 14% (20/147) of segments treated with 24Gy/fraction (fx), 20-23Gy/fx and ≤19Gy/ fx, respectively. Multivariate analysis identified dose per fx (p=0.005), baseline VCF (p<0.001) and spinal misalignment (p=0.002) as predictors of VCF. Prior conventional radiotherapy (p=0.029) was found to be protective.

Conclusions: 18% of osteolytic RCC spinal metastases fractured post-SBRT. The presence of a baseline fracture, spinal mal-alignment and treatment with ≥20Gy/fx predicted for VCF.

Keywords: vertebral compression fracture; renal cell carcinoma; spine metastases; lytic bone metastases; spine stereotactic radiosurgery; spine stereotactic body radiotherapy; intensity-modulated radiation therapy; robotic radiosurgery; radiotherapy; side effects; spine instability neoplastic score

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