Adverse Outcomes After Palliative Radiation Therapy for Uncomplicated Spine Metastases: Role of Spinal Instability and Single-Fraction Radiation Therapy.
OBJECTIVE
Level I evidence demonstrates equivalent pain response after single-fraction (SF) or multifraction (MF) radiation therapy (RT) for bone metastases. The purpose of this study is to provide additional data to inform the 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. The spinal instability neoplastic score (SINS) was used 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 neurologic symptoms, or cord compression. Fine and Gray's multivariable model assessed associations of the primary outcome with SINS, SF RT, and other significant baseline factors. Propensity score matched analysis 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, and 23.6% at 180 days. For MF RT (n=233), the incidence was 3.5%, 6.4%, and 9.2%, respectively. In multivariable analysis, SF RT (hazard ratio [HR] = 2.8, 95% confidence interval [CI] 1.5-5.2, P=.001) and SINS ≥ 11 (HR=2.5 , 95% CI 1.3-4.9, P=.007) were predictors of the incidence of first SAE. In propensity score matched analysis, first SAEs had developed in 22% of patients with SF RT versus 6% of those with MF RT cases (HR=3.9, 95% CI 1.6-9.6, P=.003) at 90 days after RT.


CONCLUSIONS
In uncomplicated spinal metastases treated with RT alone, spinal instability with SINS ≥ 11 and SF RT were associated with a higher rate of SAEs.
Department of Radiation Oncology, Dana-Farber/Brigham and Women's Cancer Center, Boston, Massachusetts. Electronic address: lamtaichung@gmail.com.
Tai-Chung
TC
Lam
Department of Biostatistics and Computational Biology, Dana-Farber Cancer Institute, Boston, Massachusetts.
Hajime
H
Uno
Department of Radiation Oncology, Dana-Farber/Brigham and Women's Cancer Center, Boston, Massachusetts.
Monica
M
Krishnan
Department of Radiation Oncology, Blanchard Valley Regional Medical Center, Findlay, Ohio.
Steven
S
Lutz
Department of Neurosurgery, Brigham and Women's Hospital, Boston, Massachusetts.
Michael
M
Groff
Harvard Radiation Oncology Program, Boston, Massachusetts.
Matthew
M
Cheney
Department of Radiation Oncology, Dana-Farber/Brigham and Women's Cancer Center, Boston, Massachusetts; Department of Psychosocial Oncology and Palliative Care, Dana-Farber Cancer Institute, Boston, Massachusetts.
Tracy
T
Balboni
D000368:Aged; D001416:Back Pain / Q000209:etiology; D005260:Female; D006760:Hospitalization; D006801:Humans; D007593:Joint Instability / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D010166:Palliative Care; D057216:Propensity Score; D011878:Radiotherapy / Q000009:adverse effects; D011879:Radiotherapy Dosage; D000069475:Re-Irradiation / Q000009:adverse effects; D012189:Retrospective Studies; D016879:Salvage Therapy / Q000379:methods; D013117:Spinal Cord Compression; D013122:Spinal Diseases / Q000209:etiology*; D016103:Spinal Fractures / Q000453:epidemiology / Q000209:etiology*; D013125:Spinal Neoplasms / Q000532:radiotherapy* / Q000556:secondary