Radiol Oncol 2024; 58(3): 425-431. doi: 10.2478/raon-2024-0033
425
research article 
Vertebral body collapse after spine stereotactic 
body radiation therapy: a single-center 
institutional experience
Arsh Issany1, Austin J Iovoli2, Richard Wang3, Rohil Shekher2, Sung Jun Ma2,  
Victor Goulenko2, Fatemeh Fekrmandi2, Dheerendra Prasad2
1 Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, New York, USA
2 Department of Radiation Medicine, Roswell Park Comprehensive Cancer Center, New York, USA
3 Kirk Kerkorian School of Medicine, University of Nevada, Las Vegas, USA
Radiol Oncol 2024; 58(3): 425-431.
Received 26 December 2023 
Accepted 26 April 2024
Correspondence to: Assoc. Prof. Dheerendra Prasad, M.D., Roswell Park Comprehensive Cancer Center, 665 Elm St Buffalo, NY 14203., USA. 
E-mail: Dheerendra.Prasad@RoswellPark.org
Disclosure: No potential conflicts of interest were disclosed. 
This is an open access article distributed under the terms of the CC-BY license (https://creativecommons.org/licenses/by/4.0/).
Background. Spine stereotactic body radiation therapy (SBRT) for the treatment of metastatic disease is increasingly 
utilized owing to improved pain and local control over conventional regimens. Vertebral body collapse (VBC) is an 
important toxicity following spine SBRT. We investigated our institutional experience with spine SBRT as it relates to VBC 
and spinal instability neoplastic score (SINS). 
Patients and methods. Records of 83 patients with 100 spinal lesions treated with SBRT between 2007 and 2022 
were reviewed. Clinical information was abstracted from the medical record. The primary endpoint was post-treat-
ment VBC. Logistic univariate analysis was performed to identify clinical factors associated with VBC. 
Results. Median dose and number of fractions used was 24 Gy and 3 fractions, respectively. There were 10 spine 
segments that developed VBC (10%) after spine SBRT. Median time to VBC was 2.4 months. Of the 11 spine segments 
that underwent kyphoplasty prior to SBRT, none developed subsequent VBC. No factors were associated with VBC 
on univariate analysis. 
Conclusions. The rate of vertebral body collapse following spine SBRT is low. Prophylactic kyphoplasty may provide 
protection against VBC and should be considered for patients at high risk for fracture.
Key words: spine metastasis; stereotactic body radiation therapy; vertebral compression fracture; kyphoplasty; spinal 
instability
Introduction
About a third of cancer patients will develop bone 
metastases during the course of their disease.1 The 
most common site of bone metastasis is the spine, 
which can often present with back pain, vertebral 
body collapse (VBC), radiculopathy, and epidural 
spinal cord compression.2 Compression of the spi-
nal cord has the potential to cause serious harm 
with symptoms ranging from pain to paralysis.2 
Optimal management of spine metastases involves 
multidisciplinary collaboration between surgeons, 
medical oncologists, pain specialists, and radiation 
oncology. For patients who are not candidates for 
immediate neurosurgical intervention, manage-
ment often involves palliative radiotherapy with 
the goal of providing symptomatic relief of pain 
and preventing further progression of disease. 
With technological advancements in the delivery 
of radiotherapy, stereotactic body radiation thera-
py (SBRT) has emerged as an effective technique 
to safely treat spinal metastases with high doses of 
Radiol Oncol 2024; 58(3): 425-431.
Issany A et al. / Vertebral body collapse after spine SBRT426
radiation while sparing surrounding healthy tis-
sue.3 
Delivery of spine SBRT involves precise treat-
ment planning and patient setup utilizing comput-
ed topography image verification to ensure the ra-
diation is delivered conformally to the target. The 
advantages of treating malignant spine metastases 
with SBRT is controversial. A recent meta-analysis 
showed the overall pain response may be similar 
compared to conventional external beam radio-
therapy (cEBRT), but more patients had complete 
pain alleviation with SBRT.4 Other studies have 
shown advantages of SBRT compared to cEBRT 
such as improved local control and pain relief.5-7 
With advances in systemic therapies improving 
survival for many types of malignancies, local con-
trol of all metastatic disease has become increas-
ingly important. Several drawbacks to spine SBRT, 
however, are increased risks of pain flare and ra-
diation induced VBC. Current literature suggests 
the rate of VBC is between 4% and 39% for patients 
with metastatic disease undergoing spine SBRT.8-13 
Chronic pain and kyphotic deformity caused by 
VBC may lead to depression, impaired mobility, 
and reduced quality of life.14 One study also found 
no clinically relevant differences between conven-
tional radiotherapy and SBRT at 12 weeks for glob-
al quality of life, physical functioning, emotional 
functioning, functional interference, and psycho-
social aspects.15 This necessitates further explora-
tion into the side effects of SBRT. 
Multiple risk factors for VBC following spine 
SBRT have been identified, which include verte-
bral body involvement, kyphotic/scoliotic spine 
deformity, lytic tumor, lung and hepatocellular 
histology, and single-fraction SBRT to a dose of 20 
Gy or higher.9,16 In developing a tool to predict the 
risk of VBC after spine SBRT, epidural tumor ex-
tension, lumbar location, gross tumor volume, and 
spinal instability neoplastic score (SINS) of more 
than 6 were associated with increased risk of frac-
ture.17 While risk factors and predictive models are 
helpful in identifying patients at high risk of VBC, 
it remains unclear how to best reduce fracture in-
cidence while also providing effective palliation.
Kyphoplasty is a minimally invasive procedure 
used in the management of VBC that uses an in-
flatable balloon to restore bone height then inject 
bone cement into the vertebral body.18 This has 
been shown to be safe and effective for controlling 
pain in patients with spine metastases.19,20 Few 
studies have investigated the effect of prophylac-
tic kyphoplasty prior to spine SBRT on reducing 
the risk of VBC. The purpose of the present study 
is to expand on the published experience of spine 
SBRT and review our single-institution outcomes 
of spine SBRT with and without prophylactic ky-
phoplasty as it relates to SINS and VBC. 
Patients and methods
Study population
The patient cohort was derived from all patients 
who received spine SBRT at a single institution 
between March 2007 and May 2022. Patients with 
tumors on the spinal cord or dura were excluded. 
The primary endpoint was development of VBC 
following completion of spine SBRT, defined as 
a new VBC or progression of an existing VBC. 
Data were collected under a protocol (BDR 157322) 
approved by the Institutional Review Board at 
Roswell Park Comprehensive Cancer Center. The 
Strengthening the Reporting of Observational 
Studies in Epidemiology (STROBE) reporting 
guideline was followed.
Patient data and treatment
Pertinent clinicopathologic data were abstracted 
from the electronic medical record for patients 
treated with spine SBRT. Clinically relevant 
variables included gender, race, age, Karnofsky 
Performance Status (KPS), primary malignancy, 
SINS, kyphoplasty performed, paraspinal exten-
sion, treatment dose, and treatment fractionation. 
SINS was calculated for each vertebral segment 
treated per published criteria using tumor location, 
pain, bone lesion type, radiographic spinal align-
ment, VBC, and posterolateral involvement of spi-
nal elements.21 Pre-treatment and post-treatment 
computed tomography (CT) and magnetic reso-
nance imaging (MRI) of the spine was reviewed to 
obtain pertinent data. Data was collected from the 
radiation consultation visit prior to the delivery 
of SBRT and at the time of first imaging follow up 
after treatment completion. Dose prescribed was 
at the discretion of the treating radiation oncolo-
gist based on pertinent clinicopathologic factors. 
Institutional protocols outlining dose constraints 
to surrounding tissue were followed. There was 
no maximum dose constraint in the target as long 
as all dose constraints were met. Eclipse (Varian 
Medical Systems, Palo Alto, CA, USA) was used for 
the generation and evaluation of radiation treat-
ment plans. We contoured clinical target volume 
(CTV) and planning target volume (PTV) accord-
ing to Consensus Contouring Guidelines.22 SBRT 
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Issany A et al. / Vertebral body collapse after spine SBRT 427
TABLE 1. Baseline patient characteristics and treatment information
VBC
(N = 10) %
No VBC
(N = 90) %
Total
(N = 100) %
Median follow up, month (IQR)
(n = 100) 10.9 3.9-18.6 12.5 5.1-27.2 12.1 5.0-25.5
Sex (n = 83)*
    Male 5 56% 37 50% 42 51%
    Female 4 44% 37 50% 41 49%
Median age, year (IQR) (n = 83)* 67 63-70 69 59-75 68 59−74
Race (n = 83)
    White 8 89% 69 93% 77 93%
    Black 2 22% 1 1% 3 4%
    Other/unknown 0 0% 3 4% 3 4%
KPS (n = 83)*
    ≥ 80 9 90% 70 95% 79 95%
    < 80 1 10% 3 4% 4 5%
Primary tumor (n = 100)**
    Lung 4 40% 25 28% 29 29%
    Renal 1 10% 23 26% 24 24%
    Breast 1 10% 8 9% 9 9%
    Prostate 2 20% 10 11% 12 12%
    Melanoma 0 0% 2 2% 2 2%
    Other 2 20% 22 24% 24 24%
    Spine Level (n = 100)**
    Cervical 1 10% 14 16% 15 15%
    Thoracic 6 60% 58 64% 64 64%
    Lumbosacral 3 30% 18 20% 21 21%
Kyphoplasty pre-SBRT (n = 100)**
    Yes 0 0% 11 12% 11 11%
    No 10 100% 79 88% 89 89%
Paraspinal extension (n = 100)**
    Yes 4 40% 36 40% 40 40%
    No 6 60% 54 60% 60 60%
Total dose (Gy)/fractions (n = 100)**
    12−17/1 1 10% 12 13% 13 13%
    10−24/2 0 0% 2 2% 2 2%
    15−30/3 8 80% 61 68% 69 69%
    20−30/4-5 1 10% 15 17% 16 16%
Dose (Gy) per fraction (n = 100)**
    < 8 4 40% 31 34% 35 35%
    8−12 5 50% 50 56% 55 55%
    13−17 1 10% 9 10% 10 10%
IQR = interquartile range; KPS = Karnofsky performance status; SBRT = stereotactic body radiation therapy; VBC = vertebral body collapse
* Categories with designation (n = 100) are lesion-level variables; ** Categories with (n = 83) are patient variables
Radiol Oncol 2024; 58(3): 425-431.
Issany A et al. / Vertebral body collapse after spine SBRT428
was delivered with a Varian TrueBeam utilizing 
online cone beam CT imaging, high definition 
multileaf collimator, and a 6 degrees of freedom 
couch.
Statistics
Univariate logistic regression using the log-rank 
method was used to identify factors associated 
with development of VBC.  All p-values were two-
sided and variables with p < 0.05 were considered 
statistically significant. Statistical Analysis was 
conducted using R (version 4.2.0, R Project for 
Statistical Computing, Vienna, Austria).
Ethical statement
The authors are accountable for all aspects of the 
work in ensuring that questions related to the ac-
curacy or integrity of any part of the work are ap-
propriately investigated and resolved. The study 
was conducted in accordance with the Declaration 
TABLE 2. Pre-treatment patient spinal instability neoplastic score (SINS) outcomes
VBC (n=10) % No VBC(n = 90) %
Total
(n = 100) %
Location
    Junctional (O-C2; C7−T2; T11−L1; L5−S1) 3 30% 32 36% 35 35%
    Mobile spine (C3−6; L2−4) 3 30% 18 20% 21 21%
    Semirigid (T3−10) 4 40% 40 44% 44 44%
    Rigid (S2−5) 0 0% 0 0% 0 0%
Mechanical pain
    Yes 5 50% 49 54% 54 54%
    No 3 30% 30 33% 33 33%
    Pain-free lesion 2 20% 11 12% 13 13%
Bone lesion
    Lytic 8 80% 71 79% 79 79%
    Mixed (lytic/blastic) 1 10% 9 10% 10 10%
    Blastic 1 10% 10 11% 11 11%
Radiographic spinal alignment
    Subluxation/translation present 0 0% 8 9% 8 8%
    Deformity (kyphosis/scoliosis) 2 20% 17 19% 19 19%
    Normal 8 80% 65 72% 73 73%
Vertebral body collapse (p = 0.040)
    > 50% collapse 0 0% 9 10% 9 9%
    < 50% collapse 1 10% 8 9% 9 9%
    No collapse with > 50% body involved 1 10% 38 42% 39 39%
    None of the above 8 80% 35 39% 43 43%
Posterolateral involvement
    Bilateral 0 0% 5 6% 5 5%
    Unilateral 6 60% 33 37% 39 39%
    None of the above 4 40% 52 58% 56 56%
SINS classification
    Stable 4 40% 22 24% 26 26%
    Potentially instability 6 60% 63 70% 69 69%
    Unstable 0 0% 5 6% 5 5%
VBC = vertebral body collapse
Radiol Oncol 2024; 58(3): 425-431.
Issany A et al. / Vertebral body collapse after spine SBRT 429
of Helsinki (as revised in 2013). The study was 
approved by the institutional review board of 
Roswell Park Comprehensive Cancer Center (BDR 
157322).
Results
A total of 83 patients with 100 treated spine seg-
ments were included for analysis. There were 10 
patients with simultaneously treated synchronous 
metastases and 7 patients with metachronous me-
tastases. Baseline patient characteristics and treat-
ment details are described in Table 1. The median 
age was 68 years (interquartile range [IQR], 59−74) 
and 51% of patients were male. Median follow up 
time was 12.1 months (IQR, 5.0−25.5). The most 
common primary tumor histology treated was 
lung (29%), followed by renal (24%) and prostate 
(12%). Median dose and number of fractions used 
was 24 Gy and 3 fractions, respectively. Categories 
with (n = 100) are lesion-level variables and cate-
gories with (n = 83) are patient variables. The 100 
lesions were assumed independent events for pa-
tients with multiple lesions. SINS for each spine 
segment prior to SBRT are summarized in Table 2.
Following SBRT there were 10 spine segments 
that developed VBC (10%), 9 which were de novo 
VBC and 1 that was progression of a prior VBC. 
Median time to VBC was 2.4 months (IQR, 0.9−4.0). 
Of the 11 spine segments that underwent kyphop-
lasty prior to SBRT, none developed subsequent 
VBC. No clinical or SINS factors were associated 
with VBC upon univariate analysis.
Discussion
This study reviewed a large single-institutional 
experience with spine SBRT through evaluation of 
VBC and SINS. As implementation of spine SBRT 
into practice continues to evolve, there is greater 
need for tools to identify patients at highest risk 
of adverse events such as VBC. We report the risk 
of VBC to be 10%, which agrees with other stud-
ies that found the risk to range from 4% to 39%.8-13 
The wide range of published VBC rates likely owes 
to differences in treatment technique and patient 
selection. Unlike previous reports, our study was 
unable to identify additional clinical or SINS fac-
tors associated with VBC. A systematic review of 
studies examining risk of VBC post-SBRT and re-
porting risk factors identified lytic disease, base-
line VBC prior to SBRT, higher dose per fraction 
SBRT, spinal deformity, older age, and more than 
40% to 50% of vertebral body involved by tumor to 
be the most frequent factors associated with VBC 
on Multivariable analysis.23 
Management of a radiation induced VBC can 
be challenging and may require surgical inter-
vention. In a review of patients developing VBC 
after spine SBRT, they found that 32% of patients 
needed a salvage spinal reconstruction procedure, 
consisting primarily of percutaneous cement aug-
mentation procedures in 77% of patients while the 
remaining patients required open spinal recon-
structive surgery.24 Method of salvage intervention 
is institutionally dependent and will vary based 
on resources available, clinical factors, and patient 
performance status. While spinal instrumentation 
may provide greater stability than cement aug-
mentation procedures such as kyphoplasty, these 
are more invasive procedures and typically result 
in more post-operative pain.
A key finding from our study is no post-treat-
ment VBC occurred in patients that underwent 
prophylactic kyphoplasty prior to SBRT. While 
kyphoplasty prior to spine SBRT has previously 
been shown to be safe and effective in small se-
ries, neither reported rates of subsequent VBC.25,26 
In agreement with these findings, another study 
found the incidence of VBC to be lower in patients 
that underwent surgical intervention or vertebro-
TABLE 3. Logistic univariate analysis of factors associated with vertebral body 
collapse
Univariate 
analysis
p-value
Gender 0.60
Age (≥ 68 v.s < 67) 0.89
KPS (≥ 80 vs. < 80) 0.38
Spine level (cervical v.s thoracic) 0.74
Spine Level (cervical vs. lumbosacral) 0.48
Spine Level (thoracic vs. lumbosacral) 0.53
Paraspinal extension 1.00
Dose per fraction (< 9 Gy v.s ≥ 9 Gy) 0.43
Location (rigid/semi-rigid vs mobile/junctional spine) 0.79
Mechanical pain 0.79
Lytic vs non-lytic bone lesion 0.93
Spinal alignment (normal vs. kyphosis/scoliosis) 0.96
Posterolateral involvement 0.29
CI = confidence interval; HR = Hazard ratio; KPS = Karnofsky performance status; SBRT = 
stereotactic body radiation therapy
Radiol Oncol 2024; 58(3): 425-431.
Issany A et al. / Vertebral body collapse after spine SBRT430
plasty prior to SBRT.17 The optimal timing and pa-
tient selection for kyphoplasty in those undergo-
ing spine SBRT still remains under investigation. 
By utilizing previously identified risk factors, pa-
tients at high risk of fracture should be considered 
for kyphoplasty to protect them from complica-
tions prior to ablative therapy with SBRT. 
Limitations
This study has multiple limitations. As with any 
retrospective study, there may be loss of data and 
miscoding during abstraction from the medical re-
cord. Additionally, our cohort was limited by the 
number of patients included. The sample size and 
low number of VBC events may not have been suf-
ficient to confirm previously identified risk factors 
for VBC with statistical significance. Another limi-
tation is the heterogeneity of patient clinical factors 
and years treated, which resulted in variation in 
how patients were approached with SBRT and dif-
ferent follow-up imaging protocols. Despite these 
limitations, this study presents valuable data dem-
onstrating low rates of VBC following spine SBRT 
and the potential protective effects of prophylactic 
kyphoplasty on further reducing this rate in ap-
propriately selected patients. Furthermore, some 
patients didn’t receive ablative dose to vertebra, 
only palliative dose was delivered. One patient re-
ceived only 2x5 Gy and there are few with 5x4 Gy 
fractionation.
Conclusions
The rate of vertebral body collapse following spine 
SBRT is low. Prophylactic kyphoplasty may pro-
vide protection against VBC and should be consid-
ered for patients at high risk for fracture. 
Acknowledgements
Funding support
This project is supported in part by funding from 
the National Cancer Institute of the National 
Institutes of Health under Award number: 
R25CA181003. The funding sources had no role in 
the preparation of this manuscript.
Author contributions
Arsh Issany: Data Curation, Investigation, Formal 
Analysis, Writing - Original Draft. Austin J. Iovoli: 
Supervision, Writing – Review & Editing. Richard 
Wang: Data Curation, Writing – Review & Editing. 
Rohil Shekher: Methodology, Writing – Review & 
Editing. Sung Jun Ma: Methodology, Supervision, 
Writing – Review & Editing. Victor Goulenko: 
Writing – Review & Editing. Fatemeh Fekrmandi: 
Writing – Review & Editing. Dheerendra Prasad: 
Conceptualization, Validation, Supervision, 
Writing – Review & Editing.
Data sharing
Research data are stored in an institutional reposi-
tory and will be shared upon request to the cor-
responding author.
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