1567. Evaluating Kyphosis with and without Stabilization Surgery Using Multifraction Stereotactic Body Radiation Therapy for Spine Metastases
Authors: Krisztina Moldovan, MD; Jonathan Nakhla, MD; Yaroslav Gelfand, MD; Rafael De La Garza Ramos, MD; Sean Barber, MD; Sanjay Konakondla, MD; Jared Fridley, MD; Albert Telfeian, MD, PhD; Ziya Gokaslan, MD; Jaroslaw Hepel, MD; Adetokunbo Oyelese, MD, PhD (Providence, RI)
Kyphosis is a known complication of pathological fractures treated with multifraction stereotactic body radiation therapy (SBRT). Single-fraction radiation surgery for spine metastases is highly effective; however, the outcomes and long-term complication of kyphosis has not been evaluated.
All patients who were treated with SBRT for spine metastases at our institution between 2009 and 2017 were retrospectively analyzed. SBRT was delivered in 2 to 5 fractions using the Cyberknife System. Two groups of lesions were analyzed: the ones who underwent stabilization surgery, and the ones that did not undergo stabilization. Patients were followed clinically and with MRI every 3 to 6 months. Vertebral body fractures (VBF) and kyphosis were evaluated and univariate analysis was used to assess the relationship between development of kyphosis at the treatment level and stabilization procedures.
A total of 98 spine lesions in 89 patients were reviewed with a median follow-up of 7.6 months. Histologies included non-small cell lung cancer (24%), renal cell carcinoma (18%), and breast cancer (12%). Surgery or vertebroplasty were performed before SBRT in 21% of cases. Higher prescribed dose, higher biologic effective dose, higher minimum dose to 90% of the planning target volume, tumor histology, and smaller tumor volume predicted improved local control. VBF occurred in 4.2% of all cases and 5.3% of those without surgery or vertebroplasty prior to SBRT. Only preexisting VBF predicted risk of post-SBRT VBF (P < .01). Out of 90 lesions that were not subject to stabilization 12 (13.3%) developed kyphosis, as compared to 0 out of 8 lesions in the stabilization group.
Although the statistical significance was not reached comparing kyphosis in stabilization and non-stabilization groups (p=0.270), we propose that since none of the lesions in the stabilization group resulted in kyphosis, stabilization surgery is superior in preventing kyphotic deformity in SBRT.