Neurosurg Rev DOI 10.1007/s10143-016-0706-y
ORIGINAL ARTICLE
Is there a relationship between spinal instability in neoplastic disease and Tokuhashi scoring system? Matheus Fernandes de Oliveira 1 & Jose Marcus Rotta 1 & Ricardo Vieira Botelho 1
Received: 29 August 2015 / Accepted: 27 January 2016 # Springer-Verlag Berlin Heidelberg 2016
Abstract Spinal instability neoplastic score (SINS) classification evaluates spinal stability by adding together six radiographic and clinical components. The objective of this study was to verify the association between SINS and Tokuhashi scoring system (TSS) score. Fifty-eight patients with vertebral metastases were admitted from 2010 to 2014 at Hospital do Servidor Público Estadual de São Paulo. They were evaluated according to their SINS and Tokuhashi SS score. Fourteen patients (24.13 %) scored from 0 to 6 points (stable spine), 37 (63.79 %) scored from 7 to 12 (potentially unstable), and 7 (12.06 %) scored from 13 to 18 (unstable). In stable spine patients according to SINS, the mean TSS score was 9.2. In potentially unstable spine patients, the mean TSS score was 8.24. In unstable spine patients, mean TSS score was 6.28. There was a statistically significant difference of the TSS score between stable and unstable patients. After evaluating TSS score in each patient, the worse the SINS, the worse was also the TSS score. Keywords Cancer . Neoplasm metastasis . Prognosis . Spine . Surgical procedures
Introduction Spinal metastatic disease is a prevalent condition, present in up to 50 % of patients with malignancies, and has become * Matheus Fernandes de Oliveira [email protected]
1
Department of Neurosurgery, Hospital do Servidor Público Estadual de São Paulo, IAMSPE, Av. Loefgren, 700, apto 103, Vila Clementino, Indianópolis, São Paulo 04040-000, Brazil
even more important as advances in cancer therapy have allowed patients to live longer [1–5]. Such metastases may lead to spinal cord compression, resulting in a diverse range of neurologic syndromes and impairing quality of life [6–10]. Vertebral involvement in such patients is associated with worse morbidity and mortality rates, impairing prognosis [11–15]. Quantification of vertebral involvement, vertebral canal invasion, neurological status, general health status, mechanical stability, and prognosis of the underlying malignancy, as determined by primary tumor histology, are paramount factors for surgical planning and definition of therapeutic targets and strategies. In this context, multidisciplinary evaluation is mandatory [16–19]. Instability due to metastatic involvement of the spine must be addressed with stabilization surgery [20–23]. The spinal instability neoplastic score (SINS) classification was designed to facilitate efficient communication among medical professionals involved in the management of metastatic spinal disease, thus guiding optimal approaches [10–12, 24]. Additionally, the Tokuhashi scoring system (TSS) is the tool used most widely to determine prognosis for survival [2, 12, 20, 21]. The objective of this study was to verify the association between SINS and TSS score. The alternative hypothesis is that patients with low Tokuhashi SS score are associated with worst instability in SINS.
Methods To test our initial hypothesis, we used a prospectively collected data from a database of patients with metastatic spinal disease, which was previously applied in other studies. Those patients were consecutively admitted from July 2010 to January 2014. This project was approved by the Hospital do
Neurosurg Rev
Servidor Público Estadual de São Paulo (HSPE) Research Ethics Committee. Inclusion criteria include consecutive patients attending to a spinal surgery section with a diagnosis of metastatic spinal disease who accepted to participate in the study. Exclusion criteria include any other spinal lesions, like primary tumors or infection.
Table 1 SINS classification based on Fisher et al. [10]
Parameter Location Junctional (occiput–C2, C7–T2, T11–L1, L5–S1) Mobile spine (C3–C6, L2–L4) Semirigid (T3–T10)
Clinical assessment All patients underwent complete clinical and neurological examinations and were classified according to Karnofsky scale (KS), Frankel scale, level involved (cervical, thoracic, lumbar, or sacral), and histology. They were also evaluated according to their SINS and TSS score.
Score
3 2 1
Rigid (S2–S5) Pain
0
Yes
3
Occasional but not mechanical Pain free lesion
1 0
Bone lesion Lytic
2
Mixed Blastic
1 0
Radiograph spinal alignment Subluxation/translation De novo deformity (kyphosis/ scoliosis) Normal alignment Vertebral body collapse
SINS evaluation The SINS evaluates spinal stability by adding six radiographic and clinical components for a score ranging from 0 to 18 (Table 1). The total score stratifies patients into three categories of stability: stable (0–6 points), potentially unstable (7–12 points), and unstable (13–18 points). In addition, the SINS can also be analyzed as a binary indicator of surgical referral status: stable (0–6 points) or current or possible instability (7–18 points). Surgical consultation is recommended for those patients with a score of ≥7.
>50 % collapse 50 % body involvement None of the above Posterolateral spinal elements involvement Bilateral Unilateral None of the above
TSS evaluation The system adds six radiographic and clinical components for a total score ranging from 0 to 15 [2, 12, 20, 21]. The extent and complexity of disease management depends on the patient’s prognosis and life expectancy: patients with life expectancies of less than 6 months (score 0–8) are treated conservatively or with palliative surgery, those with a life expectancy of 6 to 12 months (score 9–11) are candidates for palliative surgery, and in those with a life expectancy greater than 12 months (score 12–15), excision surgery is recommended. In this study, we evaluated the association between TSS scores as a function of SINS category (stable, potentially unstable, and unstable). Statistics Numerical data were described as means ± standard deviations. Categorical data were expressed as percentages. The Kolmogorov-Smirnov test was used to assess the normality of data distribution. Student’s t test and ANOVA were used for statistical analysis. The Bonferroni test was used as a post hoc test. The significance level was established as p < 0.05.
5 2 0 3 2 1 0
3 1 0
Results Fifty-eight consecutive patients (21 females and 37 males) with spinal metastases were admitted to HSPE and evaluated between July 2010 and January 2014. The mean age was 61.38 ± 12.83 years for women and 63.08 ± 9.82 years for men, with no significant gender difference (p > 0.05). All patients underwent neurological and clinical evaluations. Neurologically, 5 patients presented with a complete deficit (Frankel A), 2 with Frankel B, 25 with Frankel C, 10 with Frankel D, and 16 with Frankel E (Fig. 1). KS varied from 30 to 90. Two patients presented with a KS of 30, 6 with a score of 40, 12 patients with a score of 50, 19 patients with a score of 60, 5 patients with a score of 70, 10 patients with a score of 80, and 4 patients with a score of 90 (Fig. 2). Vertebral metastases were localized in the thoracic spine in 82 % of cases, the lumbar spine in 50 %, the cervical spine in 26 %, and the sacral spine in 10 %.
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Fig. 1 Frankel scale in patients
Fig. 3 Histology of primary cancer in patients
All patients had a known histopathological diagnosis. The primary tumor site was the prostate in 15, the breast in 12, and the lung in 10. Six patients had multiple myeloma, 6 had nonHodgkin’s lymphoma, 3 had colon cancer, and 2 had laryngeal cancers. Bladder, kidney, thyroid, and testicular cancers were diagnosed in 1 patient each (Fig. 3).
Forty-nine patients (84.4 %) presented with lytic lesions, 9 (15.6 %) with mixed lesions, and none with exclusively blastic lesions. Four patients (6.8 %) presented with subluxation, 12 (20.5 %) with de novo deformity, and 42 (72.7 %) with preserved alignment.
SINS categorization
Table 2 SINS subgroup descriptive analysis
We administered the SINS to all 58 patients. Scores ranged from 4 to 18, with a mean of 9.15 ± 3.29. Fourteen patients (24.13 %) scored 0 to 6 points (stable spine), 37 (63.79 %) scored from 7 to 12 (potentially unstable), and 7 (12.06 %) scored from 13 to 18 (unstable). SINS subgroup analysis We evaluated each domain of the SINS. Overall, 37 patients (63.8 %) presented with painful metastases, 20 (34.5 %) with occasional but not mechanical pain, and 1 (1.7 %) with no pain. Twenty-one (35.8 %) patients presented with lesions in the junctional spine, 6 (9.9 %) in the mobile spine, 30 (51.3 %) in the semirigid spine, and 2 (3.0 %) in the rigid spine. Forty-two percent of patients presented with multiple metastases; in these cases, the location with the highest SINS score was chosen for purposes of analysis (Table 2).
Fig. 2 Karnofsky score (KS) in patients
Parameter
Location Junctional (occiput–C2, C7–T2, T11–L1, L5–S1) Mobile spine (C3–C6, L2–L4) Semirigid (T3–T10) Rigid (S2–S5) Pain Yes Occasional but not mechanical Pain free lesion Bone lesion
Percentage of patients
35.8
9.9 51.3 3.0 63.8 34.5 1.7
Lytic
84.4
Mixed Blastic Radiograph spinal alignment Subluxation/translation De novo deformity (kyphosis/scoliosis) Normal alignment Vertebral body collapse >50 % collapse 50 % body involvement None of the above Posterolateral spinal elements involvement Bilateral Unilateral None of the above
15.6 0 6.8 20.5 72.7 17.3 27.5 50 5.2
56.8 31.1 12.1
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Fig. 4 Several images of metastatic spinal disease, showing different patterns of spinal involvement
Ten patients (17.3 %) presented with more than 50 % vertebral collapse, 16 (27.5 %) with less than 50 % collapse, 29 (50 %) with no collapse and more than 50 % of vertebral involvement, and 3 (5.2 %) with none of the above. Thirtythree patients (56.8 %) presented with bilateral involvement of posterolateral spinal elements, 18 (31.1 %) with unilateral involvement, and 7 (12.1 %) with no involvement (Fig. 4).
Discussion The classic study of White and Panjabi defined spinal stability as the ability of the spine to maintain its degree of motion while simultaneously preventing pain, neurologic deficit, and abnormal angulation. Spinal instability created by neoplastic processes appears to be different from that associated with traumatic injuries. It is an ill-defined clinical entity based on symptoms, signs, and imaging findings [24–28].
Correlation between SINS and TSS TSS scores ranged from 3 to 14, with a mean of 8.48 ± 2.29. In patients with spines classified as stable (SINS), the mean TSS score was 9.2 ± 2.39. In patients with potentially unstable spines, the mean TSS score was 8.24 ± 2.08. In patients with unstable spines, the mean TSS score was 6.28 ± 0.95. No patient with unstable spine presented with a TSS score greater than 8. There was a statistically significant difference of the TSS score between stable and unstable patients (p = 0.01). There was no significant difference between stable and potentially unstable patients (p = 0.46) or between potentially unstable and unstable patients (p = 0.08) (Fig. 5).
Fig. 5 Evaluation of TSS according to SINS category. Unstable spine had statistical significant difference (p < 0.05) of TSS score in comparison to stable spine
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NOMS (neurologic, oncologic, mechanical instability, systemic disease) criteria for decision-making have been used to guide clinicians in choosing between radiation and surgical treatment for metastatic spine tumors. The mechanical instability component of these criteria relies solely on the assessment of a patient’s movement-related pain. Different types of motions and postures are characteristic of mechanical pain and thus defined as instability by NOMS [29–32]. The SINS was designed to evaluate the stability in metastatic spinal disease, with a sensitivity and specificity of 95.7 and 79.5 %, respectively, for potentially unstable or unstable lesions [10–12, 18, 24]. Reliability among different evaluations is approximately 70 % [25]. Impending spinal instability is also an important factor that affects the clinical decisionmaking process in oncologic spinal disease. The role of surgery in the setting of neurologic deficit and spinal cord compression with metastatic disease is well established [4, 5]. However, in patients with metastatic spinal disease but no neurologic deficit, it is important for clinical and radiation oncologists, radiologists, and spine surgeons to recognize which situations are unstable or may lead to spinal instability and neurologic injury. This will allow proper stabilization of patients with severe mechanical pain and will hopefully prevent painful collapse, neurologic consequences, and inappropriate treatment planning for patients with impending instability. On applying SINS to our sample, we found scores ranging from 4 to 18 (mean, 9.15 ± 3.29). Overall, 24.13 % of patients were classified as having a stable spine, 63.79 % as potentially unstable, and 12.06 % as unstable. This analysis reveals that most patients with metastatic disease have impaired spine stability, and approximately three quarters of these patients may be candidates for specialist evaluation and spinal stabilization surgery. Analysis of each SINS domain separately showed that most of patients presented with painful metastases (63.7 %). While pain-free lesions may indicate less severe cancer status, they may also be present in neurologically impaired patients (Frankel A), due to sensory tract injury. Forty-two percent of our patients presented with metastases in multiple segments. The semirigid spine was the most common site of diagnosis, followed by junctional, mobile, and rigid spine. Intrinsic metastatic lesions are mainly lytic in nature; mixed lesions are possible, but purely blastic lesions are exceedingly rare. This corroborates the bone instability caused by metastases. Among our patients, half presented with preserved alignment, followed by de novo deformity and few cases of subluxation. Most also presented with no vertebral collapse. Posterior element involvement was observed in most patients, once again demonstrating a trend toward diffuse disease. After evaluating the TSS score in each patient, we concluded that, the worse the SINS, the worse is the TSS score as well.
No patient with unstable spine had a TSS score above 8, which would contraindicate excision surgery according to the TSS. This result is probably not coincident, as both scores grade metastatic disease impact and are, somehow, related. Thus, patients who are optimal candidates for stabilization surgery according to SINS are also those with the worst TSS scores, usually predicting less than 3–6 months of survival, which could contraindicate surgery. This finding should be addressed in future discussions. The clinical importance of this work is to reveal that SINS score should not be used isolated but associated to one concomitant survival prognostic evaluation in order to the best clinical decision. This study was performed in a single center. These results must be tested in other centers. In conclusion, application of the SINS and TSS score to a sample of patients with metastatic spinal disease revealed that the majority of such patients present with potentially unstable or unstable spines. However, those patients who would be candidates for stabilization surgery are simultaneously those with the worst prognosis.
Compliance with ethical standards Conflict of interest The authors declare that they have no competing interests.
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ORIGINAL ARTICLE
Is there a relationship between spinal instability in neoplastic disease and Tokuhashi scoring system? Matheus Fernandes de Oliveira 1 & Jose Marcus Rotta 1 & Ricardo Vieira Botelho 1
Received: 29 August 2015 / Accepted: 27 January 2016 # Springer-Verlag Berlin Heidelberg 2016
Abstract Spinal instability neoplastic score (SINS) classification evaluates spinal stability by adding together six radiographic and clinical components. The objective of this study was to verify the association between SINS and Tokuhashi scoring system (TSS) score. Fifty-eight patients with vertebral metastases were admitted from 2010 to 2014 at Hospital do Servidor Público Estadual de São Paulo. They were evaluated according to their SINS and Tokuhashi SS score. Fourteen patients (24.13 %) scored from 0 to 6 points (stable spine), 37 (63.79 %) scored from 7 to 12 (potentially unstable), and 7 (12.06 %) scored from 13 to 18 (unstable). In stable spine patients according to SINS, the mean TSS score was 9.2. In potentially unstable spine patients, the mean TSS score was 8.24. In unstable spine patients, mean TSS score was 6.28. There was a statistically significant difference of the TSS score between stable and unstable patients. After evaluating TSS score in each patient, the worse the SINS, the worse was also the TSS score. Keywords Cancer . Neoplasm metastasis . Prognosis . Spine . Surgical procedures
Introduction Spinal metastatic disease is a prevalent condition, present in up to 50 % of patients with malignancies, and has become * Matheus Fernandes de Oliveira [email protected]
1
Department of Neurosurgery, Hospital do Servidor Público Estadual de São Paulo, IAMSPE, Av. Loefgren, 700, apto 103, Vila Clementino, Indianópolis, São Paulo 04040-000, Brazil
even more important as advances in cancer therapy have allowed patients to live longer [1–5]. Such metastases may lead to spinal cord compression, resulting in a diverse range of neurologic syndromes and impairing quality of life [6–10]. Vertebral involvement in such patients is associated with worse morbidity and mortality rates, impairing prognosis [11–15]. Quantification of vertebral involvement, vertebral canal invasion, neurological status, general health status, mechanical stability, and prognosis of the underlying malignancy, as determined by primary tumor histology, are paramount factors for surgical planning and definition of therapeutic targets and strategies. In this context, multidisciplinary evaluation is mandatory [16–19]. Instability due to metastatic involvement of the spine must be addressed with stabilization surgery [20–23]. The spinal instability neoplastic score (SINS) classification was designed to facilitate efficient communication among medical professionals involved in the management of metastatic spinal disease, thus guiding optimal approaches [10–12, 24]. Additionally, the Tokuhashi scoring system (TSS) is the tool used most widely to determine prognosis for survival [2, 12, 20, 21]. The objective of this study was to verify the association between SINS and TSS score. The alternative hypothesis is that patients with low Tokuhashi SS score are associated with worst instability in SINS.
Methods To test our initial hypothesis, we used a prospectively collected data from a database of patients with metastatic spinal disease, which was previously applied in other studies. Those patients were consecutively admitted from July 2010 to January 2014. This project was approved by the Hospital do
Neurosurg Rev
Servidor Público Estadual de São Paulo (HSPE) Research Ethics Committee. Inclusion criteria include consecutive patients attending to a spinal surgery section with a diagnosis of metastatic spinal disease who accepted to participate in the study. Exclusion criteria include any other spinal lesions, like primary tumors or infection.
Table 1 SINS classification based on Fisher et al. [10]
Parameter Location Junctional (occiput–C2, C7–T2, T11–L1, L5–S1) Mobile spine (C3–C6, L2–L4) Semirigid (T3–T10)
Clinical assessment All patients underwent complete clinical and neurological examinations and were classified according to Karnofsky scale (KS), Frankel scale, level involved (cervical, thoracic, lumbar, or sacral), and histology. They were also evaluated according to their SINS and TSS score.
Score
3 2 1
Rigid (S2–S5) Pain
0
Yes
3
Occasional but not mechanical Pain free lesion
1 0
Bone lesion Lytic
2
Mixed Blastic
1 0
Radiograph spinal alignment Subluxation/translation De novo deformity (kyphosis/ scoliosis) Normal alignment Vertebral body collapse
SINS evaluation The SINS evaluates spinal stability by adding six radiographic and clinical components for a score ranging from 0 to 18 (Table 1). The total score stratifies patients into three categories of stability: stable (0–6 points), potentially unstable (7–12 points), and unstable (13–18 points). In addition, the SINS can also be analyzed as a binary indicator of surgical referral status: stable (0–6 points) or current or possible instability (7–18 points). Surgical consultation is recommended for those patients with a score of ≥7.
>50 % collapse 50 % body involvement None of the above Posterolateral spinal elements involvement Bilateral Unilateral None of the above
TSS evaluation The system adds six radiographic and clinical components for a total score ranging from 0 to 15 [2, 12, 20, 21]. The extent and complexity of disease management depends on the patient’s prognosis and life expectancy: patients with life expectancies of less than 6 months (score 0–8) are treated conservatively or with palliative surgery, those with a life expectancy of 6 to 12 months (score 9–11) are candidates for palliative surgery, and in those with a life expectancy greater than 12 months (score 12–15), excision surgery is recommended. In this study, we evaluated the association between TSS scores as a function of SINS category (stable, potentially unstable, and unstable). Statistics Numerical data were described as means ± standard deviations. Categorical data were expressed as percentages. The Kolmogorov-Smirnov test was used to assess the normality of data distribution. Student’s t test and ANOVA were used for statistical analysis. The Bonferroni test was used as a post hoc test. The significance level was established as p < 0.05.
5 2 0 3 2 1 0
3 1 0
Results Fifty-eight consecutive patients (21 females and 37 males) with spinal metastases were admitted to HSPE and evaluated between July 2010 and January 2014. The mean age was 61.38 ± 12.83 years for women and 63.08 ± 9.82 years for men, with no significant gender difference (p > 0.05). All patients underwent neurological and clinical evaluations. Neurologically, 5 patients presented with a complete deficit (Frankel A), 2 with Frankel B, 25 with Frankel C, 10 with Frankel D, and 16 with Frankel E (Fig. 1). KS varied from 30 to 90. Two patients presented with a KS of 30, 6 with a score of 40, 12 patients with a score of 50, 19 patients with a score of 60, 5 patients with a score of 70, 10 patients with a score of 80, and 4 patients with a score of 90 (Fig. 2). Vertebral metastases were localized in the thoracic spine in 82 % of cases, the lumbar spine in 50 %, the cervical spine in 26 %, and the sacral spine in 10 %.
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Fig. 1 Frankel scale in patients
Fig. 3 Histology of primary cancer in patients
All patients had a known histopathological diagnosis. The primary tumor site was the prostate in 15, the breast in 12, and the lung in 10. Six patients had multiple myeloma, 6 had nonHodgkin’s lymphoma, 3 had colon cancer, and 2 had laryngeal cancers. Bladder, kidney, thyroid, and testicular cancers were diagnosed in 1 patient each (Fig. 3).
Forty-nine patients (84.4 %) presented with lytic lesions, 9 (15.6 %) with mixed lesions, and none with exclusively blastic lesions. Four patients (6.8 %) presented with subluxation, 12 (20.5 %) with de novo deformity, and 42 (72.7 %) with preserved alignment.
SINS categorization
Table 2 SINS subgroup descriptive analysis
We administered the SINS to all 58 patients. Scores ranged from 4 to 18, with a mean of 9.15 ± 3.29. Fourteen patients (24.13 %) scored 0 to 6 points (stable spine), 37 (63.79 %) scored from 7 to 12 (potentially unstable), and 7 (12.06 %) scored from 13 to 18 (unstable). SINS subgroup analysis We evaluated each domain of the SINS. Overall, 37 patients (63.8 %) presented with painful metastases, 20 (34.5 %) with occasional but not mechanical pain, and 1 (1.7 %) with no pain. Twenty-one (35.8 %) patients presented with lesions in the junctional spine, 6 (9.9 %) in the mobile spine, 30 (51.3 %) in the semirigid spine, and 2 (3.0 %) in the rigid spine. Forty-two percent of patients presented with multiple metastases; in these cases, the location with the highest SINS score was chosen for purposes of analysis (Table 2).
Fig. 2 Karnofsky score (KS) in patients
Parameter
Location Junctional (occiput–C2, C7–T2, T11–L1, L5–S1) Mobile spine (C3–C6, L2–L4) Semirigid (T3–T10) Rigid (S2–S5) Pain Yes Occasional but not mechanical Pain free lesion Bone lesion
Percentage of patients
35.8
9.9 51.3 3.0 63.8 34.5 1.7
Lytic
84.4
Mixed Blastic Radiograph spinal alignment Subluxation/translation De novo deformity (kyphosis/scoliosis) Normal alignment Vertebral body collapse >50 % collapse 50 % body involvement None of the above Posterolateral spinal elements involvement Bilateral Unilateral None of the above
15.6 0 6.8 20.5 72.7 17.3 27.5 50 5.2
56.8 31.1 12.1
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Fig. 4 Several images of metastatic spinal disease, showing different patterns of spinal involvement
Ten patients (17.3 %) presented with more than 50 % vertebral collapse, 16 (27.5 %) with less than 50 % collapse, 29 (50 %) with no collapse and more than 50 % of vertebral involvement, and 3 (5.2 %) with none of the above. Thirtythree patients (56.8 %) presented with bilateral involvement of posterolateral spinal elements, 18 (31.1 %) with unilateral involvement, and 7 (12.1 %) with no involvement (Fig. 4).
Discussion The classic study of White and Panjabi defined spinal stability as the ability of the spine to maintain its degree of motion while simultaneously preventing pain, neurologic deficit, and abnormal angulation. Spinal instability created by neoplastic processes appears to be different from that associated with traumatic injuries. It is an ill-defined clinical entity based on symptoms, signs, and imaging findings [24–28].
Correlation between SINS and TSS TSS scores ranged from 3 to 14, with a mean of 8.48 ± 2.29. In patients with spines classified as stable (SINS), the mean TSS score was 9.2 ± 2.39. In patients with potentially unstable spines, the mean TSS score was 8.24 ± 2.08. In patients with unstable spines, the mean TSS score was 6.28 ± 0.95. No patient with unstable spine presented with a TSS score greater than 8. There was a statistically significant difference of the TSS score between stable and unstable patients (p = 0.01). There was no significant difference between stable and potentially unstable patients (p = 0.46) or between potentially unstable and unstable patients (p = 0.08) (Fig. 5).
Fig. 5 Evaluation of TSS according to SINS category. Unstable spine had statistical significant difference (p < 0.05) of TSS score in comparison to stable spine
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NOMS (neurologic, oncologic, mechanical instability, systemic disease) criteria for decision-making have been used to guide clinicians in choosing between radiation and surgical treatment for metastatic spine tumors. The mechanical instability component of these criteria relies solely on the assessment of a patient’s movement-related pain. Different types of motions and postures are characteristic of mechanical pain and thus defined as instability by NOMS [29–32]. The SINS was designed to evaluate the stability in metastatic spinal disease, with a sensitivity and specificity of 95.7 and 79.5 %, respectively, for potentially unstable or unstable lesions [10–12, 18, 24]. Reliability among different evaluations is approximately 70 % [25]. Impending spinal instability is also an important factor that affects the clinical decisionmaking process in oncologic spinal disease. The role of surgery in the setting of neurologic deficit and spinal cord compression with metastatic disease is well established [4, 5]. However, in patients with metastatic spinal disease but no neurologic deficit, it is important for clinical and radiation oncologists, radiologists, and spine surgeons to recognize which situations are unstable or may lead to spinal instability and neurologic injury. This will allow proper stabilization of patients with severe mechanical pain and will hopefully prevent painful collapse, neurologic consequences, and inappropriate treatment planning for patients with impending instability. On applying SINS to our sample, we found scores ranging from 4 to 18 (mean, 9.15 ± 3.29). Overall, 24.13 % of patients were classified as having a stable spine, 63.79 % as potentially unstable, and 12.06 % as unstable. This analysis reveals that most patients with metastatic disease have impaired spine stability, and approximately three quarters of these patients may be candidates for specialist evaluation and spinal stabilization surgery. Analysis of each SINS domain separately showed that most of patients presented with painful metastases (63.7 %). While pain-free lesions may indicate less severe cancer status, they may also be present in neurologically impaired patients (Frankel A), due to sensory tract injury. Forty-two percent of our patients presented with metastases in multiple segments. The semirigid spine was the most common site of diagnosis, followed by junctional, mobile, and rigid spine. Intrinsic metastatic lesions are mainly lytic in nature; mixed lesions are possible, but purely blastic lesions are exceedingly rare. This corroborates the bone instability caused by metastases. Among our patients, half presented with preserved alignment, followed by de novo deformity and few cases of subluxation. Most also presented with no vertebral collapse. Posterior element involvement was observed in most patients, once again demonstrating a trend toward diffuse disease. After evaluating the TSS score in each patient, we concluded that, the worse the SINS, the worse is the TSS score as well.
No patient with unstable spine had a TSS score above 8, which would contraindicate excision surgery according to the TSS. This result is probably not coincident, as both scores grade metastatic disease impact and are, somehow, related. Thus, patients who are optimal candidates for stabilization surgery according to SINS are also those with the worst TSS scores, usually predicting less than 3–6 months of survival, which could contraindicate surgery. This finding should be addressed in future discussions. The clinical importance of this work is to reveal that SINS score should not be used isolated but associated to one concomitant survival prognostic evaluation in order to the best clinical decision. This study was performed in a single center. These results must be tested in other centers. In conclusion, application of the SINS and TSS score to a sample of patients with metastatic spinal disease revealed that the majority of such patients present with potentially unstable or unstable spines. However, those patients who would be candidates for stabilization surgery are simultaneously those with the worst prognosis.
Compliance with ethical standards Conflict of interest The authors declare that they have no competing interests.
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