METASTATIC SPINE DISEASE
SINS Classification | NOMS Framework | Bilsky Grading | Surgical Management
SINS SCORE INTERPRETATION
Critical Must-Knows
- SINS score determines mechanical stability (0-6 stable, 7-12 consult, 13-18 unstable)
- Bilsky grading assesses epidural cord compression (0-3, 1c or higher needs evaluation)
- NOMS framework integrates Neurologic, Oncologic, Mechanical, Systemic factors
- Radioresistant tumors: RCC, thyroid, melanoma require SBRT not conventional RT
- Separation surgery enables post-op SBRT for high-grade epidural disease
Examiner's Pearls
- "SINS 13 or higher = unstable spine requiring surgical stabilization
- "Bilsky 1c or higher in radioresistant tumor = surgical evaluation
- "MESCC is oncological emergency - steroids immediately, surgery within 24-48h
- "Ambulatory status at presentation predicts neurological outcome
Clinical Imaging
Imaging Gallery
Critical Metastatic Spine Exam Points
SINS Score
Calculate SINS in every viva - know the 6 components: Location (junctional=3), Pain (mechanical=3), Bone lesion (lytic=2), Alignment (subluxation=4), VB collapse (over 50%=3), Posterolateral (bilateral=3). Score 13 or higher = unstable requiring surgery.
Bilsky Grading
Bilsky 1c is key threshold - cord contact without compression. In radioresistant tumors (RCC, thyroid, melanoma), Bilsky 1c or higher needs surgical evaluation for separation surgery to enable SBRT.
NOMS Framework
Systematic approach - N: Neurologic (Bilsky, deficit), O: Oncologic (radiosensitivity), M: Mechanical (SINS), S: Systemic (ECOG, life expectancy). Each component independently influences treatment decisions.
Radiosensitivity
Know tumor types - Radiosensitive: lymphoma, myeloma, SCLC. Radioresistant: RCC, thyroid, melanoma, sarcoma, HCC. Radioresistant tumors have 30-40% local failure with conventional RT.
Radiosensitive vs Radioresistant Tumors
| Feature | Radiosensitive | Radioresistant |
|---|---|---|
| Examples | Lymphoma, myeloma, SCLC, seminoma | RCC, thyroid, melanoma, sarcoma, HCC |
| Conventional RT | Effective (60-70% local control) | Poor (30-40% failure at 1 year) |
| SBRT Required | No (unless progression) | Yes for durable control |
| Bilsky 1c Management | May observe/RT | Separation surgery + SBRT |
| Preop Embolization | Not typically needed | Essential for RCC, thyroid (hypervascular) |
At a Glance
Metastatic spine disease affects 10-30% of cancer patients, with 70% occurring in the thoracic spine due to red marrow distribution. The SINS score (6 components: location, pain, lesion type, alignment, vertebral body collapse, posterolateral involvement) determines mechanical stability—scores ≥13 require surgical stabilization. The NOMS framework integrates Neurologic (Bilsky grading), Oncologic (radiosensitivity), Mechanical (SINS), and Systemic factors for treatment decisions. BPLTK primaries (Breast, Prostate, Lung, Thyroid, Kidney) account for 80% of cases. Radioresistant tumors (RCC, thyroid, melanoma) require separation surgery with SBRT rather than conventional radiation for durable local control.
SINS Score Components
Memory Hook:SINS-CP: Score 0-6 stable, 7-12 consult, 13-18 unstable (requires surgery)
NOMS Framework
Memory Hook:Never Operate without Multidisciplinary Support - integrate all factors
BPLTK Primary Tumors
Memory Hook:BPLTK account for 80% of all spine metastases
Overview and Epidemiology
Metastatic spine disease is the most common neoplasm of the spine, representing 90% of all spinal tumors. It significantly impacts quality of life through pain, neurological dysfunction, and mechanical instability.
Epidemiology:
- 10-30% of cancer patients develop spinal metastases
- Spine is the most common site of skeletal metastasis (Batson's plexus)
- Thoracic spine most common (70%), followed by lumbar (20%), cervical (10%)
- 5-10% of metastatic spine patients develop MESCC
- Breast, prostate, lung, thyroid, kidney (BPLTK) = 80% of cases
Distribution by Level:
| Region | Frequency | Unique Considerations |
|---|---|---|
| Thoracic | 70% | Kyphotic deformity, rib involvement |
| Lumbar | 20% | Cauda equina, psoas involvement |
| Cervical | 10% | High morbidity, vertebral artery |
| Sacral | Rare | Pelvic organs, sacral nerve roots |
Anatomical Pattern of Involvement:
- Vertebral body: 85% of lesions (anterior column)
- Pedicles: 60% involvement
- Posterior elements: 40% involvement
- Isolated posterior elements: Under 5%
Batson's Plexus
The valveless paravertebral venous plexus allows direct retrograde tumor spread from pelvic/abdominal organs to spine, bypassing the pulmonary filter. This explains the high frequency of spine metastases from prostate, breast, and lung primaries.
Pathophysiology
Metastatic Cascade
The metastatic process to spine involves:
- Local invasion - Primary tumor invades local vasculature
- Intravasation - Tumor cells enter circulation
- Survival - Evade immune surveillance in bloodstream
- Extravasation - Exit at distant sites (Batson's plexus key role)
- Colonization - Establish micrometastasis in marrow
- Angiogenesis - Develop blood supply for growth
Bone Lesion Types
Osteolytic Metastases (Most Common)
Characterized by bone destruction via osteoclast activation:
- Mechanism: Tumor secretes PTHrP, IL-6, IL-11 activating osteoclasts
- Radiographic appearance: Punched-out lesions, cortical destruction
- Common primaries: Lung, thyroid, renal cell, melanoma
- SINS implication: Score 2 (higher instability risk)
- Pathological fracture: High risk with over 50% VB involvement
Lytic lesions cause rapid structural compromise and high fracture risk.
Primary Tumor Characteristics
| Primary | Lesion Type | Vascularity | Radiosensitivity | Median Survival |
|---|---|---|---|---|
| Breast | Mixed/Lytic | Moderate | Moderate | 24-36 months |
| Prostate | Blastic | Low | Moderate | 24-36 months |
| Lung | Lytic | Moderate | Radiosensitive | 6-12 months |
| Renal | Lytic | HIGH | Radioresistant | 12-24 months |
| Thyroid | Lytic | HIGH | Radioresistant | 24-48 months |
| Myeloma | Lytic | Low | Radiosensitive | 24-36 months |
| Melanoma | Lytic | Moderate | Radioresistant | 6-12 months |
Hypervascular Tumors
RCC and thyroid metastases are highly vascular. Preoperative embolization is essential to reduce intraoperative blood loss. Consider embolizing 24-48 hours before surgery when operatively managing these tumors.
Classification Systems
SINS - Spinal Instability Neoplastic Score
SINS Score Components (Maximum 18 points):
| Component | Score | Description |
|---|---|---|
| Location | ||
| Junctional (C0-C2, C7-T2, T11-L1, L5-S1) | 3 | Highest instability risk |
| Mobile spine (C3-C6, L2-L4) | 2 | Moderate risk |
| Semi-rigid (T3-T10) | 1 | Lower risk (rib cage support) |
| Rigid (S2-S5) | 0 | Minimal risk |
| Mechanical Pain | ||
| Yes (movement-related) | 3 | Suggests structural compromise |
| Non-mechanical (occasional) | 1 | Less concerning |
| Pain-free | 0 | Favorable |
| Bone Lesion | ||
| Lytic | 2 | Highest fracture risk |
| Mixed lytic/blastic | 1 | Intermediate |
| Blastic | 0 | More stable |
| Radiographic Alignment | ||
| Subluxation/translation | 4 | Critical instability |
| De novo deformity (kyphosis/scoliosis) | 2 | Significant |
| Normal | 0 | Favorable |
| Vertebral Body Collapse | ||
| Collapse over 50% | 3 | Severe compromise |
| Collapse under 50% | 2 | Moderate |
| No collapse but over 50% body involved | 1 | At risk |
| None of above | 0 | Intact |
| Posterolateral Element Involvement | ||
| Bilateral | 3 | Highest instability |
| Unilateral | 1 | Moderate |
| None | 0 | Stable |
SINS Interpretation:
- 0-6: Stable - no surgical consultation required
- 7-12: Potentially unstable - surgical consultation recommended
- 13-18: Unstable - surgical stabilization required
Bilsky Epidural Compression Scale
| Grade | Description | Management |
|---|---|---|
| 0 | Bone-only disease | Radiation if indicated |
| 1a | Epidural impingement, no thecal deformation | Radiation alone |
| 1b | Thecal sac deformed, no cord contact | Radiation alone |
| 1c | Cord contact without compression | Surgical evaluation |
| 2 | Cord compression, CSF visible | Surgical decompression |
| 3 | Cord compression, no CSF (circumferential) | Urgent surgery |
Bilsky 1c Threshold
Bilsky 1c is the critical decision point. In radioresistant tumors (RCC, thyroid, melanoma), Bilsky 1c or higher requires surgical evaluation for separation surgery to enable safe delivery of SBRT.
NOMS Decision Framework
N - Neurologic Assessment
Evaluates neural compression and functional status:
Bilsky Grade:
- Grade 0-1b: No significant neural compromise
- Grade 1c-3: Progressive compression requiring intervention
Functional Status:
- Frankel/ASIA Grade (A-E)
- Ambulatory status (critical prognostic factor)
- Bladder/bowel function
Time-Critical:
- Rapid progression under 48 hours = urgent decompression
- Motor deficit under 48 hours = best surgical outcomes
- Complete paralysis over 24-48 hours = poor recovery
Ambulatory status at presentation is strongest predictor of outcome.
Clinical Presentation
History
Pain Patterns:
- Mechanical pain: Worse with movement - suggests instability (SINS +3)
- Biological pain: Night pain, constant, progressive - tumor burden
- Radicular pain: Dermatomal distribution - nerve root compression
- Myelopathic symptoms: Gait difficulty, coordination problems
Red Flags for Metastatic Disease:
- Age over 50 with new back pain
- Known cancer history (even remote)
- Unexplained weight loss (over 10% in 6 months)
- Night pain unrelieved by position
- Progressive neurological symptoms
- Pain unresponsive to conservative treatment
Physical Examination
Neurological Assessment (Essential):
- Motor: Myotomal testing, document Frankel/ASIA grade
- Sensory: Dermatomal assessment, sensory level
- Reflexes: Hyperreflexia (UMN) vs hyporeflexia (LMN)
- Long tract signs: Hoffman's, Babinski, clonus
- Gait: Ambulatory status is critical prognostic factor
Spinal Examination:
- Tenderness over involved levels
- Palpable step-off or deformity
- Paraspinal muscle spasm
MESCC - Oncological Emergency
Metastatic Epidural Spinal Cord Compression:
- 5-10% of cancer patients develop MESCC
- Neurological deterioration can be rapid (hours to days)
- Time to treatment = neurological outcome
MESCC Emergency
MESCC is an oncological emergency. Patients ambulatory at presentation have 75-90% chance of remaining ambulatory with treatment. Non-ambulatory patients have only 10-30% chance of regaining ambulation. Start steroids immediately, expedite imaging and surgical consultation.
Investigations
Laboratory Studies
Essential Tests:
- CBC, CMP, LFTs (baseline, nutritional status)
- Calcium (hypercalcemia common in bone mets)
- Tumor markers (PSA, CEA, CA 19-9, AFP)
- SPEP/UPEP (exclude myeloma)
- HIV (if unknown primary)
Imaging
MRI - Gold Standard:
- Sensitivity: 98.5% for osseous metastases
- Specificity: 98.9%
- Sequences: T1, T2, STIR, post-gadolinium
- Findings:
- T1 hypointense (marrow replacement)
- T2 hyperintense (tumor/edema)
- Gadolinium enhancement
- Epidural extension (Bilsky grading)
CT Scan:
- Bone architecture assessment
- Cortical destruction visualization
- Surgical planning (pedicle trajectory)
- CT-guided biopsy
Plain Radiographs:
- Limited sensitivity (30-50% bone loss required)
- Alignment assessment
- Standing views for sagittal balance
Nuclear Medicine:
- Bone scan: Sensitive but non-specific
- PET-CT: Staging, treatment response
- SPECT: Improved localization
Biopsy
Indications:
- Unknown primary
- Solitary lesion (exclude primary tumor)
- Atypical imaging features
- No other accessible biopsy site
Management
Corticosteroid Protocol
Dexamethasone for MESCC:
| Dose | Indication |
|---|---|
| 10mg IV bolus | Initial presentation |
| 4mg IV/PO q6h | Maintenance until definitive Rx |
| 96mg bolus | Severe/rapid progression (selected cases) |
Mechanism: Reduces vasogenic edema, possible tumoricidal effect on lymphoma
Non-Operative Management
Indications:
- SINS 0-6 (stable)
- Bilsky 0-1b with radiosensitive tumor
- Poor surgical candidate (ECOG 3-4)
- Life expectancy under 3 months
External Beam Radiation (cEBRT)
Regimens:
- 30 Gy in 10 fractions (standard)
- 20 Gy in 5 fractions (hypofractionated)
- 8 Gy single fraction (palliation)
Outcomes:
- Pain relief: 70-80%
- Motor improvement: 40-60%
- Local control (radiosensitive): 60-70%
Limitations:
- 30-40% failure for radioresistant tumors
- Dose constraint near spinal cord
cEBRT effective for radiosensitive tumors and pain palliation.
Surgical Management
Indications for Surgery:
- Mechanical instability (SINS 13-18)
- High-grade ESCC (Bilsky 2-3) with deficit
- Radioresistant tumor with Bilsky 1c or higher
- Progressive deficit despite radiation
- Pathological fracture with canal compromise
- Tissue diagnosis needed
Separation Surgery:
- Create 2-3mm gap around cord for safe SBRT
- Posterior approach with instrumentation
- Circumferential decompression (not GTR)
- Post-op SBRT within 2-4 weeks
- 1-year local control: 85-95%
Surgical Approaches:
- Posterior: Most common, extensile, pedicle screws
- Anterior: Corpectomy, cervical plating
- MIS: Percutaneous screws, vertebroplasty
Instrumentation:
- Minimum 2 levels above/below lesion
- Cement augmentation in poor bone
- Expandable cages for anterior column
Complications
Surgical Complications
General:
- Wound infection: 5-10%
- DVT/PE: 5-15%
- Medical complications: 10-20%
- 30-day mortality: 5-10%
Spine-Specific:
- Hardware failure: 5-10%
- Adjacent level fracture: 5-15%
- Neurological deterioration: 2-5%
- CSF leak: 2-5%
Wound Issues:
- Higher risk with prior radiation
- May require plastic surgery
Radiation Complications
Acute:
- Radiation dermatitis
- Esophagitis (thoracic)
- Nausea, fatigue
Late:
- Radiation myelopathy (rare with modern techniques)
- Vertebral compression fracture (10-15% post-SBRT)
Disease Progression
Local Recurrence:
- cEBRT alone (radioresistant): 30-40% at 1 year
- SBRT: 5-15% at 1 year
- Separation surgery + SBRT: 5-10% at 1 year
Evidence Base
Patchell Trial - Surgery + RT vs RT Alone
- Randomized 101 patients with single-level MESCC
- Surgery + RT: 84% ambulatory vs RT alone: 57% (p=0.001)
- Median ambulation time: 122 vs 13 days
- Study excluded radiosensitive tumors
RTOG 0631 - SBRT vs cEBRT
- SBRT 16-18 Gy vs cEBRT 8 Gy single fraction
- Pain response at 3 months: SBRT 41% vs cEBRT 23%
- Statistically significant difference (p=0.01)
- Complete pain response higher with SBRT
SINS Validation
- 30 spine oncology experts developed and validated SINS
- Inter-observer reliability: kappa 0.76 (substantial)
- Intra-observer reliability: kappa 0.86 (almost perfect)
- Scores 7-12 showed highest variability
Separation Surgery Outcomes
- 186 patients with high-grade ESCC
- Separation surgery followed by SBRT
- 1-year local control: 90%
- Neurological improvement: 73%
- 30-day mortality: 5%
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
SINS Calculation and Management
"A 58-year-old man with metastatic prostate cancer has T8 vertebral body lesion with 30% collapse, no epidural extension, 4 weeks of mechanical back pain. No neurological symptoms."
MESCC Emergency
"The same patient returns 3 months later with 2 days of progressive leg weakness. Examination: 3/5 bilateral LE power, hyperreflexia, upgoing plantars. MRI shows T8 with Bilsky grade 2."
Radioresistant Tumor Management
"A 62-year-old woman with metastatic RCC has L2 lytic lesion, 60% collapse, kyphotic deformity, Bilsky 1c. Intact neurology. Calculate SINS and outline management."
Limited Life Expectancy
"A 75-year-old with ECOG 3, multiple visceral metastases from lung cancer, life expectancy 6-8 weeks. Severe mechanical back pain from L3 pathological fracture. SINS 10, Bilsky 0."
METASTATIC SPINE DISEASE
High-Yield Exam Summary
SINS Score Components
- •Location: Junctional=3, Mobile=2, Semi-rigid=1, Rigid=0
- •Pain: Mechanical=3, Non-mechanical=1, None=0
- •Bone: Lytic=2, Mixed=1, Blastic=0
- •Alignment: Subluxation=4, Deformity=2, Normal=0
- •VB Collapse: Over 50%=3, Under 50%=2, Over 50% involved=1, None=0
- •Posterolateral: Bilateral=3, Unilateral=1, None=0
- •INTERPRETATION: 0-6 stable, 7-12 consult, 13-18 unstable
Bilsky Grading
- •Grade 0: Bone only
- •Grade 1a: Epidural impingement
- •Grade 1b: Thecal deformation, no cord contact
- •Grade 1c: Cord contact (KEY THRESHOLD)
- •Grade 2: Cord compression, CSF visible
- •Grade 3: Circumferential compression, no CSF
- •1c or higher in radioresistant tumor = surgery
NOMS Framework
- •N = Neurologic: Bilsky grade, deficit, ambulatory status
- •O = Oncologic: Radiosensitivity determines RT approach
- •M = Mechanical: SINS score guides stabilization
- •S = Systemic: ECOG, life expectancy
- •Radiosensitive: Lymphoma, myeloma, SCLC
- •Radioresistant: RCC, thyroid, melanoma, sarcoma
Surgical Indications
- •SINS 13-18 (unstable) - even without neurology
- •Bilsky 2-3 with neurological deficit
- •Bilsky 1c or higher in radioresistant tumor
- •Progressive deficit despite radiation
- •Pathological fracture with instability
Key Numbers
- •Dexamethasone: 10mg bolus then 4mg q6h
- •SBRT: 24 Gy single or 27 Gy/3# or 30-35 Gy/5#
- •Pedicle screws: Minimum 2 levels above/below
- •Patchell: Surgery+RT 84% ambulatory vs RT 57%
- •SBRT local control: 85-95% at 1 year
Examiner Favorites
- •Calculate SINS explicitly in viva
- •MESCC = emergency - steroids first
- •RCC and thyroid need embolization
- •Separation surgery = decompression for SBRT
- •Match treatment to life expectancy
MCQ Practice Points
Exam Pearl
Q: What is the SINS (Spinal Instability Neoplastic Score) threshold for surgical stabilization? A: SINS 7-12 is indeterminate (requires surgical consultation); SINS greater than 12 indicates instability requiring surgical stabilization. SINS assesses location, pain, lesion type, alignment, vertebral body collapse, and posterolateral element involvement.
Exam Pearl
Q: What are the components of the NOMS framework for metastatic spine treatment decisions? A: N = Neurologic status, O = Oncologic (tumor radiosensitivity and systemic disease burden), M = Mechanical instability (SINS), S = Systemic disease and medical comorbidities. This framework guides the choice between surgery, radiation, or conservative management.
Exam Pearl
Q: What is the Tomita scoring system used for? A: Predicting survival and guiding surgical extent in metastatic spine disease. Scores 2-3 favor wide/marginal excision, 4-5 favor marginal/intralesional surgery, 6-7 favor palliative surgery, and 8-10 suggest non-operative care. Factors include primary tumor type, visceral metastases, and bone metastases number.
Exam Pearl
Q: What is separation surgery in metastatic spine disease? A: Decompression and stabilization to create a 2-3mm gap between tumor and spinal cord, allowing safe delivery of high-dose stereotactic body radiotherapy (SBRT). It is not an oncologic resection but enables effective radiation while protecting neural structures.
Australian Context
Metastatic spine disease in Australia is managed through multidisciplinary teams including orthopaedic/neurosurgical oncology, radiation oncology, medical oncology, and palliative care services. The Cancer Australia guidelines recommend systematic assessment using SINS and NOMS frameworks for treatment planning.
Australian cancer registries report that prostate, breast, and lung cancers remain the leading causes of spinal metastases, consistent with international patterns. Access to SBRT has improved in recent years with specialized radiation oncology services available in major tertiary centers.
Bone-modifying agents including bisphosphonates (zoledronic acid) and denosumab are PBS-listed for prevention of skeletal-related events in patients with bone metastases from solid tumors. Coordination with oncology teams is essential for optimal systemic therapy alongside local treatment.
References
- Fisher CG, DiPaola CP, Ryken TC, et al. A novel classification system for spinal instability in neoplastic disease. Spine. 2010;35(22):E1221-9.
- Bilsky MH, Laufer I, Fourney DR, et al. Reliability analysis of the epidural spinal cord compression scale. J Neurosurg Spine. 2010;13(3):324-8.
- Patchell RA, Tibbs PA, Regine WF, et al. Direct decompressive surgical resection in the treatment of spinal cord compression caused by metastatic cancer. Lancet. 2005;366(9486):643-8.
- Laufer I, Iorgulescu JB, Chapman T, et al. Local disease control for spinal metastases following "separation surgery." J Neurosurg Spine. 2013;18(3):207-14.
- Ryu S, Deshmukh S, Timmerman RD, et al. Radiosurgery compared to external beam radiotherapy for localized spine metastasis. Lancet Oncol. 2023;115(3):818-27.
- Barzilai O, Laufer I, Yamada Y, et al. Integrating evidence-based medicine for treatment of spinal metastases into a decision framework. J Clin Oncol. 2017;35(21):2419-27.