Spinal instability as defined by the spinal instability neoplastic score is associated with radiotherapy failure in metastatic spinal disease.
BACKGROUND
Although radiotherapy is effective in achieving pain relief in most patients, it is not completely understood why some patients respond well to radiotherapy and others do not. Our hypothesis was that metastatic bone pain, if predominantly caused by mechanical instability of the spine, responds less well to radiotherapy than metastatic bone pain caused by local tumor activity. Recently, the spinal instability neoplastic score (SINS) was proposed as a standardized referral tool for nonspine specialists to facilitate early diagnosis of spinal instability.


OBJECTIVE
To investigate the association between spinal instability as defined by the SINS and response to radiotherapy in patients with spinal metastases.


METHODS
A retrospectively matched case-control study in an academic tertiary referral center, conducted according to the Strengthening the Reporting of Observational Studies in Epidemiology guidelines.


METHODS
Thirty-eight patients with spinal metastases who were retreated after initial palliative radiotherapy from January 2009 to December 2010 were matched to 76 control patients who were not retreated.


METHODS
Radiotherapy failure as defined by retreatment (radiotherapy, surgery, and conservative) after palliative radiotherapy for spinal metastases.


METHODS
Radiotherapy planning computed tomography scans were scored by a blinded spine surgeon according to the SINS criteria. The association between SINS and radiotherapy failure was estimated by univariate and multivariate conditional logistic regression analysis.


RESULTS
Median SINS was 10 (range 4-16) for cases and 7 (range 1-16) for controls. The SINS was significantly and independently associated with radiotherapy failure (adjusted odds ratio, 1.3; 95% confidence interval, 1.1-1.5; p=.01).


CONCLUSIONS
This study shows that a higher spinal instability score increases the risk of radiotherapy failure in patients with spinal metastases, independent of performance status, primary tumor, and symptoms. These results may support the hypothesis that metastatic spinal bone pain, predominantly caused by mechanical instability, responds less well to radiotherapy than pain mainly resulting from local tumor activity.
Department of Radiology, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, The Netherlands. Electronic address: m.huisman-7@umcutrecht.nl.
Merel
M
Huisman
Department of Radiology, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, The Netherlands.
Joanne M
JM
van der Velden
Department of Radiation Oncology, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, The Netherlands.
Marco
M
van Vulpen
Department of Radiology, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, The Netherlands.
Maurice A A J
MA
van den Bosch
Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5, Canada.
Edward
E
Chow
Department of Orthopedic Surgery, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, The Netherlands.
F Cumhur
FC
Öner
Department of Orthopedic Surgery, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5, Canada.
Albert
A
Yee
Department of Radiology, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, The Netherlands.
Helena M
HM
Verkooijen
Department of Orthopedic Surgery, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, The Netherlands.
Jorrit-Jan
JJ
Verlaan
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000150:complications* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010166:Palliative Care; D012044:Regression Analysis; D012189:Retrospective Studies; D013125:Spinal Neoplasms / Q000532:radiotherapy* / Q000556:secondary; D013131:Spine / Q000473:pathology* / Q000528:radiation effects; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
Pain; Palliative care; Radiotherapy; Retreatment; Spinal instability neoplastic score; Spinal metastases