TY - JOUR
T1 - The impact of decompression with instrumentation on local failure following spine stereotactic radiosurgery
AU - Miller, Jacob A.
AU - Balagamwala, Ehsan H.
AU - Berriochoa, Camille A.
AU - Angelov, Lilyana
AU - Suh, John H.
AU - Benzel, Edward C.
AU - Mohammadi, Alireza M.
AU - Emch, Todd
AU - Magnelli, Anthony
AU - Godley, Andrew
AU - Qi, Peng
AU - Chao, Samuel T.
N1 - Publisher Copyright:
© 2017 AANS.
PY - 2017/10
Y1 - 2017/10
N2 - OBJECTIVE Spine stereotactic radiosurgery (SRS) is a safe and effective treatment for spinal metastases. However, it is unknown whether this highly conformal radiation technique is suitable at instrumented sites given the potential for microscopic disease seeding. The authors hypothesized that spinal decompression with instrumentation is not associated with increased local failure (LF) following SRS. METHODS A 2:1 propensity-matched retrospective cohort study of patients undergoing SRS for spinal metastasis was conducted. Patients with less than 1 month of radiographic follow-up were excluded. Each SRS treatment with spinal decompression and instrumentation was propensity matched to 2 controls without decompression or instrumentation on the basis of demographic, disease-related, dosimetric, and treatment-site characteristics. Standardized differences were used to assess for balance between matched cohorts. The primary outcome was the 12-month cumulative incidence of LF, with death as a competing risk. Lesions demonstrating any in-feld progression were considered LFs. Secondary outcomes of interest were post-SRS pain flare, vertebral compression fracture, instrumentation failure, and any Grade = 3 toxicity. Cumulative incidences analysis was used to estimate LF in each cohort, which were compared via Gray's test. Multivariate competing-risks regression was then used to adjust for prespecifed covariates. RESULTS Of 650 candidates for the control group, 166 were propensity matched to 83 patients with instrumentation. Baseline characteristics were well balanced. The median prescription dose was 16 Gy in each cohort. The 12-month cumulative incidence of LF was not statistically signifcantly different between cohorts (22.8% [instrumentation] vs 15.8% [control], p = 0.25). After adjusting for the prespecifed covariates in a multivariate competing-risks model, decompression with instrumentation did not contribute to a greater risk of LF (HR 1.21, 95% CI 0.74-1.98, p = 0.45). The incidences of post-SRS pain?are (11% vs 14%, p = 0.55), vertebral compression fracture (12% vs 22%, p = 0.04), and Grade = 3 toxicity (1% vs 1%, p = 1.00) were not increased at instrumented sites. No instrumentation failures were observed. CONCLUSIONS In this propensity-matched analysis, LF and toxicity were similar among cohorts, suggesting that decompression with instrumentation does not signifcantly impact the effcacy or safety of spine SRS. Accordingly, spinal instrumentation may not be a contraindication to SRS. Future studies comparing SRS to conventional radiotherapy at instrumented sites in matched populations are warranted.
AB - OBJECTIVE Spine stereotactic radiosurgery (SRS) is a safe and effective treatment for spinal metastases. However, it is unknown whether this highly conformal radiation technique is suitable at instrumented sites given the potential for microscopic disease seeding. The authors hypothesized that spinal decompression with instrumentation is not associated with increased local failure (LF) following SRS. METHODS A 2:1 propensity-matched retrospective cohort study of patients undergoing SRS for spinal metastasis was conducted. Patients with less than 1 month of radiographic follow-up were excluded. Each SRS treatment with spinal decompression and instrumentation was propensity matched to 2 controls without decompression or instrumentation on the basis of demographic, disease-related, dosimetric, and treatment-site characteristics. Standardized differences were used to assess for balance between matched cohorts. The primary outcome was the 12-month cumulative incidence of LF, with death as a competing risk. Lesions demonstrating any in-feld progression were considered LFs. Secondary outcomes of interest were post-SRS pain flare, vertebral compression fracture, instrumentation failure, and any Grade = 3 toxicity. Cumulative incidences analysis was used to estimate LF in each cohort, which were compared via Gray's test. Multivariate competing-risks regression was then used to adjust for prespecifed covariates. RESULTS Of 650 candidates for the control group, 166 were propensity matched to 83 patients with instrumentation. Baseline characteristics were well balanced. The median prescription dose was 16 Gy in each cohort. The 12-month cumulative incidence of LF was not statistically signifcantly different between cohorts (22.8% [instrumentation] vs 15.8% [control], p = 0.25). After adjusting for the prespecifed covariates in a multivariate competing-risks model, decompression with instrumentation did not contribute to a greater risk of LF (HR 1.21, 95% CI 0.74-1.98, p = 0.45). The incidences of post-SRS pain?are (11% vs 14%, p = 0.55), vertebral compression fracture (12% vs 22%, p = 0.04), and Grade = 3 toxicity (1% vs 1%, p = 1.00) were not increased at instrumented sites. No instrumentation failures were observed. CONCLUSIONS In this propensity-matched analysis, LF and toxicity were similar among cohorts, suggesting that decompression with instrumentation does not signifcantly impact the effcacy or safety of spine SRS. Accordingly, spinal instrumentation may not be a contraindication to SRS. Future studies comparing SRS to conventional radiotherapy at instrumented sites in matched populations are warranted.
KW - Local failure
KW - Oncology
KW - Spinal instrumentation
KW - Spine metastasis
KW - Stereotactic radiosurgery
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U2 - 10.3171/2017.3.SPINE161015
DO - 10.3171/2017.3.SPINE161015
M3 - Article
C2 - 28731393
AN - SCOPUS:85030678727
SN - 1547-5654
VL - 27
SP - 436
EP - 443
JO - Journal of Neurosurgery: Spine
JF - Journal of Neurosurgery: Spine
IS - 4
ER -