Adverse Outcomes after Palliative Radiation Therapy for Uncomplicated Spine Metastases: Role of Spinal Instability and Single Fraction Radiation Therapy

Background : Level I evidence demonstrates equivalent pain response after single fraction (SF) or multiple fraction (MF) radiation therapy (RT) for bone metastases. There are little data to inform incidence and predictors of adverse outcomes after RT for spine metastases. Methods : At a single institution, 299 uncomplicated spine metastases (without cord compression, prior RT or surgery) treated with RT from 2008 to 2013 were retrospectively reviewed. Spinal Instability Neoplastic Score (SINS) was employed to assess spinal instability. The primary outcome was time to first spinal adverse event (SAE) at the site, including: symptomatic vertebral fracture, hospitalization for site-related pain, salvage surgery, interventional procedure, new neurological symptoms or cord compression. Fine and Gray’s multivariable model (MVA) assessed associations of the primary outcome with SINS, SF RT, and other significant baseline factors. Propensity score matched analysis (PSMA) further assessed the relationship of SF RT to first SAEs. Results : The cumulative incidence of first SAE after SF RT (n=66) was 6.8% at 30 days, 16.9% at 90 days, 23.6% at 180 days. For MF RT (n=233), the incidence was 3.5%, 6.4% and 9.2%, respectively. In MVA, SF RT [HR=2.8 (1.5-5.2), p=0.001] and SINS≥11 [HR=2.5 (1.3-4.9), p=0.007] were predictors of the incidence of first SAE. In PSMA, first SAEs developed in 22% of SF RT versus 6% of MF RT cases [HR=3.9 (1.6-9.6), p=0.003] at 90-days post-RT. Conclusion : In uncomplicated spinal metastases treated with RT alone, spinal instability with SINS ≥11 and single fraction RT were associated with higher rate of spinal adverse events.

http://www.redjournal.org/article/S0360-3016%2815%2900619-7/abstract

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