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Metastatic Bone Disease

High EvidenceUpdated: 2025-12-25

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Red Flags

  • Back pain in a cancer patient -> Rule out Malignant Spinal Cord Compression (MSCC)
  • Severe thigh pain on weight bearing -> Impending Pathological Fracture (Mirels > 8)
  • Hypercalcaemia (Confusion, Vomiting, Polyuria) -> Oncological Emergency
Overview

Metastatic Bone Disease

1. Clinical Overview

Summary

Bone is the third most common site of metastatic spread (after lung and liver). It is a catastrophic complication of solid tumours, marking the transition to incurable, palliative disease. The "Big 5" carcinomas responsible for >80% of bone metastases are Breast, Prostate, Lung, Kidney, and Thyroid. Lesions are classified as Lytic (bone destruction), Blastic (bone formation), or Mixed. The primary goals of management are palliation of pain, prevention of Skeletal Related Events (SREs) (fractures, cord compression), and maintenance of mobility. Prophylactic surgical fixation of impending fractures, guided by the Mirels' Score, significantly improves quality of life compared to fixation of completed fractures.

Key Facts

  • Prevalence: 70% of patients with advanced Breast or Prostate cancer develop bone mets.
  • Site Trinity: Spine (>50%) -> Pelvis -> Proximal Long Bones (Femur/Humerus).
  • Mechanism: Haematogenous spread via Batson's Valveless Venous Plexus (Spine).
  • Fracture Risk: A completed pathological fracture reduces life expectancy by 50% due to immobility and surgical stress.

The "Big 5" Sources (Detailed)

  1. Breast Carcinoma:
    • Frequency: 70% of advanced breast cancer patients.
    • Type: Mixed (Lytic/Blastic).
    • Hormones: ER+/PR+ tumours have better prognosis and respond to Tamoxifen/Letrozole. HER2+ responds to Herceptin.
    • Sites: Thoracic spine, Ribs, Sternum.
  2. Prostate Carcinoma:
    • Frequency: 90% of advanced prostate cancer.
    • Type: Osteoblastic (Sclerotic).
    • Mechanism: PSA and Endothelin-1 drive osteoblasts.
    • Sites: Lumbar spine (Batson's plexus), Pelvis.
  3. Lung Carcinoma:
    • Frequency: 30-40%.
    • Type: Lytic. Very aggressive.
    • Patterns:
      • Pancoast Tumour: Apical lung tumour invading ribs/spine.
      • Acrometastasis: Metastasis to the hands/feet (rare, but lung is the commonest cause).
  4. Renal Cell Carcinoma (RCC):
    • Frequency: 20-25%.
    • Type: Lytic, Expansile ("Blow-out"), Hypervascular.
    • Features: Pulsatile mass. High risk of bleeding.
  5. Thyroid Carcinoma:
    • Type: Lytic.
    • Subtypes: Follicular (more common to bone) > Papillary.
  • Kidney (Renal): Lytic. hyper-vascular.
  • Thyroid: Lytic. Hyper-vascular.
  • Hypercalcaemia: Poor prognostic sign (Median survival < 3 months).

Clinical Pearls

"Fix it BEFORE it breaks": Prophylactic nailing of an impending femoral fracture is an elective, closed procedure with immediate weight bearing. Fixing a completed pathological fracture is a bloody, difficult operation with poor healing potential. Be aggressive with prophylaxis.

"The Renal Cell Trap": Renal Cell Carcinoma (RCC) metastases are enormously vascular. If you instrument them without embolization, the patient can exsanguinate on the table. Always embolise Renal and Thyroid metastases pre-op.

"Prostate turns it White": On X-ray, Prostate cancer metastases look like "Cotton Wool" or "Snowballs" (Sclerotic). Lung cancer looks like "Moth holes" (Lytic).

"The Biopsy Rule": In a patient >40 with a destructive bone lesion, assume metastasis until proven otherwise. Do NOT biopsy the bone primarily. Perform a CT TAP (Thorax Abdo Pelvis) to find the primary first. Biopsying a primary sarcoma erroneously can result in amputation.

"The Iceberg Effect": The lesion you see on X-ray is only the tip of the iceberg. The tumour infiltration in the marrow extends far beyond what you can see. This is why we always use long nails to span the whole bone, not just the visible hole.

"The Cortical Rule": If a lytic lesion destroys more than 50% of the cortex (the hard outer shell) on any view, the bone has lost 90% of its torsional strength. It will snap if they twist on it.

"The NNT": The Number Needed to Treat (NNT) for radiotherapy to achieve complete pain relief is about 3. For partial relief, it is nearly 1 in 1. It is incredibly effective.

2. Epidemiology

Incidence

  • Global Burden: Millions affected annually.
  • Autopsy Data: 70% of patients dying of cancer have bone involvement.
  • Survival:
    • Breast/Prostate: Median survival >2-3 years (Bone is often the only metastatic site).
    • Lung: Median survival <6 months (Highly aggressive).

Risk Factors for SREs

  • Lytic Lesions: Structurally weaker than blastic lesions.
  • Weight Bearing: Peritrochanteric femur lesions have the highest risk of failure.
  • Pain: Functional pain (pain on loading) is the most specific predictor of impending fracture.
3. Pathophysiology

The Metastatic Cascade

  1. Detach: Clonal expansion and detachment from primary tumour (loss of E-cadherin).
  2. Travel: Intravasation into blood/lymphatics. Survival in circulation (evading immune surveillance).
  3. Dock: Extravasation into bone marrow sinusoids (slow blood flow).
  4. Establish: Interaction with stromal cells ("Seed and Soil" hypothesis - Paget 1889).

The "Seed and Soil" Hypothesis (Paget, 1889)

Stephen Paget observed that breast cancer did not metastasize randomly, but favored specific organs (Bone, Liver). He proposed that tumour cells ("Seeds") need a receptive microenvironment ("Soil") to grow. In bone, this soil is the rich milieu of growth factors released by bone turnover.

The 7-Step Metastatic Cascade

Step 1: Clonal Expansion & Epithelial-Mesenchymal Transition (EMT)

  • Primary tumour cells lose adhesion (E-Cadherin downregulation).
  • They acquire a mobile phenotype (N-Cadherin upregulation).

Step 2: Intravasation

  • Invasion through the basement membrane into local blood vessels or lymphatics.
  • Facilitated by Matrix Metalloproteinases (MMPs).

Step 3: Survival in Circulation

  • Tumour cells face high shear stress and immune surveillence (NK cells).
  • Platelet Cloaking: Cells coat themselves in platelets/fibrin to hide from the immune system and arrest in capillaries.

Step 4: Arrest & Extravasation

  • Mechanical trapping in the slow-flow sinusoids of the Red Marrow (Axial skeleton).
  • Adhesion molecules (Integrins) bind to endothelial receptors (VCAM-1).

Step 5: Dormancy & Colonization

  • Cells may remain dormant (G0 phase) for years ("The Sleeping Beauty").
  • Reactivation triggers proliferation.

Step 6: The Vicious Cycle (Osteolysis)

  • Tumour cells secrete PTHrP (Parathyroid Hormone-related Protein).
  • PTHrP binds to Osteoblasts -> Upregulates RANK-L.
  • RANK-L binds to RANK on Osteoclast precursors -> Formation of Giant Multinucleated Osteoclasts.
  • Osteoclasts resorb bone, releasing trapped TGF-Beta and IGF-1.
  • TGF-Beta fuels further tumour growth -> More PTHrP.

Step 7: Sclerosis (The Osteoblastic Response)

  • In Prostate Cancer, cells secrete Endothelin-1 and Wnt proteins.
  • These stimulate Osteoblasts directly.
  • Result: Disorganized, woven bone deposition (Sclerosis). This bone is structurally weak despite being dense.

Molecular Targets in Metastasis

  1. RANK-L: The key mediator of osteoclastogenesis. Blocked by Denosumab.
  2. Integrins: Mediate adhesion to bone matrix.
  3. Cathepsin K: Enzyme used by osteoclasts to digest collagen.
  4. MMPs: Enzymes degrading the extracellular matrix.
4. Clinical Presentation

Symptoms

Physical Examination

Pain
The hallmark. Biological Pain: Worse at night. Unrelieved by rest. Caused by interosseous pressure and inflammatory mediators (Prostaglandins). Mechanical Pain: "Start-up pain" or pain on weight-bearing. Indicates structural instability (micro-fractures).
Neurological Deficit
Radiculopathy (nerve root pain) or Myelopathy (Cord compression - weakness/incontinence).
Systemic
Confusion, thirst, constipation (Hypercalcaemia).
5. Clinical Examination

The "Onco-Ortho" Assessment

  1. Look: Wasting, Deformity, Surgical scars (Mastectomy/Thyroidectomy).
  2. Feel:
    • Palpate the painful bone.
    • Percuss the Spine: A key test. Mechanical back pain is rarely tender to percussion. Mets are.
  3. Move: Range of motion (often preserved unless joint involvement).
  4. Neuro: Power (MRC grade), Sensation (Dermatomes), Reflexes.
  5. Mirels' Assessment: Assess pain severity (Mild vs Functional).
6. Investigations

Staging (Finding the Primary)

When a patient presents with a bone lesion and no known cancer history ("MUP" - Metastasis of Unknown Primary), do the following:

  1. History:
    • Weight loss? Cough (Lung)? Haematuria (Renal)? Change in bowel habit (GI)?
    • Smoker? Alcohol?
  2. Basic Exam:
    • Breast lump? Thyroid mass? Prostate (PR)? Testicular mass?
  3. The "Metastatic Screen" (Bloods):
    • FBC (Anaemia), Renal (Calcium/ALP).
    • PSA: If >100, almost certainly Prostate.
    • Myeloma Screen: Serum Electrophoresis. (Essential - Myeloma is treated very differently).
    • Tumour Markers: CEA (Bowel), CA-125 (Ovarian), CA19-9 (Pancreas), Alpha-fetoprotein (Teratoma/HCC), Beta-HCG.
  4. Imaging Hierarchy:
    • CXR: Useless for small lesions.
    • CT TAP: The workhorse. Finds 85% of primaries (Lung, Renal, GI).
    • Mammogram: If female and CT TAP normal.
    • Thyroid Ultrasound: If Ca/ALP normal and CT TAP normal.
    • PET-CT: The final problem solver. If PET is negative, biopsy the bone.

Imaging the Bone

  1. X-Ray (Plain Film):
    • Lytic: "Moth-eaten" destruction. Loss of cortical continuity.
    • Blastic: Sclerotic/White density.
    • Pathological Fracture: Transverse fracture line through a lesion.
  2. Bone Scintigraphy (Technetium-99m):
    • Mechanism: Tracer binds to Osteoblasts (Bone formation).
    • Utility: Total body screen. Good for Blastic lesions (Prostate).
    • Limitation: Can miss purely Lytic lesions (Myeloma/Lung) as there is no osteoblast reaction ("Cold lesions").
  3. MRI:
    • Gold Standard for Spine.
    • Defines extent of marrow involvement and soft tissue mass.
    • Essential for planning surgery (length of nail).
  4. PET-CT (FDG):
    • Metabolic activity. Differentiates active tumour from necrosis/infection.
    • SUVmax: High uptake indicates high grade malignancy.

The Biopsy: Rules and Risks

  • Indication: Only if CT TAP fails to find a primary, OR if the primary history is remote (>5 years).
  • Technique: Image-guided core needle biopsy.
  • Rule: Never biopsy a primary bone tumour without Sarcoma team input (Needle track seeding).
  • The "Whoops" Procedure:
    • If a surgeon accidentally nails a primary sarcoma (thinking it was a met):
    • The tumour spreads up and down the canal.
    • The hematoma contaminates the entire compartment.
    • Outcome: The patient usually requires a whole limb amputation to clear the disease.
    • Lesson: Always get imaging + staging before surgery.
7. Management Algorithm (The Impending Fracture)
        PAINFUL LYTIC LESION (Femur/Humerus)
                    ↓
             CALCULATE MIRELS' SCORE
        (Site + Pain + Size + Type)
                    ↓
        ┌───────────┴───────────┐
     SCORE &lt; 8              SCORE > 8
        ↓                       ↓
    RADIOTHERAPY           SURGERY
  (To kill tumour)       (Prophylactic Nail)
        +
  BISPHOSPHONATES

The Mirels' Scoring System

Used to predict fracture risk in long bones.

VariableScore 1Score 2Score 3
SiteUpper LimbLower LimbPeritrochanteric
PainMildModerateFunctional (Severe)
LesionBlasticMixedLytic
Size< 1/3 Diameter1/3 - 2/3> 2/3 Diameter
  • Score <= 7: Radiotherapy/Observation. (Fracture Risk <5%).
  • Score = 8: The "Grey Zone". Clinical judgement (Lean towards fixation if high activity level).
  • Score >= 9: Prophylactic Fixation Recommended. (Fracture Risk >33%).

ECOG Performance Status

Alternative to KPS.

GradeECOG
0Fully active.
1Restricted in strenuous activity. Ambulatory.
2Ambulatory (>50% of time up). Self-care capable.
3Limited self-care. Confined to bed/chair >50% of time.
4Completely disabled. Bedbound.
5Dead.

Medical Management: The Analgesic Ladder

Pain in bone mets is complex (Somatic + Neuropathic).

  1. Step 1: Non-Opioids
    • Paracetamol: 1g QDS. Baseline.
    • NSAIDs: Ibuprofen/Naproxen (Check renal function/Gastritis). Highly effective for bone pain (Prostaglandin driven).
      • Caution: Cancer patients are prone to acute kidney injury (Contrast CTs, Dehydration). Always check Creatinine before prescribing NSAIDs. Add a Proton Pump Inhibitor (Omeprazole) for stomach protection.
  2. Step 2: Weak Opioids
    • Codeine/Dihydrocodeine: 30-60mg QDS.
    • Caution: Constipation (Give laxatives).
  3. Step 3: Strong Opioids
    • Morphine/Oxycodone: Titrate to effect. (e.g. Oramorph 10mg PRN).
    • Patches: Fentanyl/Buprenorphine (Only for stable pain, takes 12h to work).
  4. Step 4: Adjuvants (Neuropathic)
    • Gabapentin/Pregabalin: For radicular nerve root pain.
    • Amitriptyline: Low dose (10mg) at night.
    • Steroids: Dexamethasone 8mg bd (Reduces tumour edema/capsule stretch).
  5. Step 5: Interventional
    • Nerve Blocks: Intercostal block (Ribs).
    • Cementoplasty: Injecting cement into a vertebral body (Vertebroplasty) heats and stabilizes the bone, killing nerve endings.

Pre-Operative Checklist

Before taking a mets patient to theatre:

  1. Bloods: FBC (Hb >100?), Platelets (>50?), Clotting (Normal?).
  2. Group and Save: Crossmatch 4 units. (RCC/Thyroid are bloody).
  3. Embolization: Confirmed done for Renal/Thyroid?
  4. Consent:
    • "Surgery is palliative".
    • Risk of death on table (Fat embolism).
    • Risk of infection (Immunosuppressed).
    • Risk of implant failure.
  5. MDT: Is the Oncologist aware? Do not operate if life expectancy < 2 weeks.

Bone Cement Implantation Syndrome (BCIS)

A catastrophic intra-operative complication.

  • Mechanism: Pressurizing cement into the femoral canal forces fat marrow emboli into the venous circulation.
  • Signs: Sudden Hypotension (Drop in BP), Hypoxia (Drop in O2 sats), Cardiac Arrest.
  • Risk Factors:
    • Elderly.
    • Metastatic disease (Pathological marrow).
    • Unvented femur.
  • Prevention:
    • Vent the Femur: Drill a hole distally.
    • Wash the canal: Perform prolonged lavage to remove fat before cementing.
    • Inform Anaesthetist: "Cement going in now". (They increase FiO2).

Management of Opioid Side Effects

If starting morphine, you MUST prescribe preventatives ("The Handshake").

  1. Constipation:
    • Universal side effect.
    • Rx: Senna (Stimulant) + Movicol (Softener). Avoid bulk formers (Fybogel) if dehydrated.
  2. Nausea:
    • Common in first 3-5 days.
    • Rx: Metoclopramide (Prokinetic) or Cyclizine. Or Haloperidol (low dose) for chemical nausea.
  3. Drowsiness:
    • Signs of overdose: Pinpoint pupils, Respiratory rate <8.
    • Rx: Naloxone (if severe). Otherwise reduce dose.

Bone Protection

  • Bisphosphonates (Zoledronic Acid): Potent osteoclast inhibitor. Reduces SREs.
  • Denosumab: Monoclonal antibody against RANK-L. Subcutaneous injection. Superior to Zometa in solid tumours.
  • Risk: Osteonecrosis of the Jaw (ONJ). Dental check mandatory.

Surgical Management

  1. Prophylactic Fixation:
    • IM Nail: Load-sharing device. Protects the entire bone (prevents fracture at a different level later).
    • Plate/Screw: Load-bearing. Generally inferior to nails for mets (screws pull out of soft bone). Use Cement augmentation.
  2. Reconstruction:
    • Endoprosthetic Replacement: For articular/metaphyseal destruction where fixation is impossible. Replace the whole joint and bone segment (Mega-prosthesis).
    • Indication: Failed fixation or massive bone loss.
  3. Spine:
    • Decompression + Stabilization: For MSCC. Pedicle screw fixation.

Post-Operative Rehabilitation

  • Weight Bearing:
    • Nail/Cemented Hip: Immediate Full Weight Bearing (FWB) as tolerated. The metal takes the load.
    • Uncemented/Plate: Restricted weight bearing (Touch toe) - Avoid these in mets if possible.
  • Physiotherapy:
    • Early mobilization prevents chest infection.
    • Assess for aids (Frame/Crutches).
  • Occupational Therapy:
    • Home assessment. Stair lift? Hospital bed?
    • Palliative discharge planning (Hospice vs Home).

Prevention of Venous Thromboembolism (DVT/PE)

Cancer patients undergoing surgery have the highest risk of PE.

  • Risk Score: Caprini Score usually >5.
  • Protocol:
    • Mechanical (TEDs/Calf pumps).
    • Chemical: LMWH (Enoxaparin) or DOAC for 28 days post-op.
    • Contraindication: If platelets <50 (due to marrow infiltration) or brain mets (bleed risk).

Technical Aspects of Fixation

  1. Long IM Nails:
    • Always span the entire bone. A short nail leaves a stress riser at the tip, where the next met will break the bone.
    • Reaming: Careful reaming allows a larger nail (stronger). However, reaming increases embolization risk.
    • Locking: Static locking is mandatory (unlike trauma where we might dynamize). The bone will not heal, so stability depends entirely on the metal.
  2. Cement Augmentation:
    • Methylmethacrylate (Bone Cement) fills void spaces.
    • Thermal Effect: The exothermic reaction (up to 70°C) causes local tumour necrosis (adjuvant effect).
    • "Concreting the cavity": Essential in peri-articular destruction.
    • Risk: Bone Cement Implantation Syndrome (BCIS) - Hypotension due to marrow fat embolization.
  3. Venting:
    • When nailing a pathologically tight canal (or cemented nail), consider drilling a "vent hole" distal to the lesion to allow marrow pressure to escape, preventing fat embolism to lungs.
  4. Harrington Procedure:
    • For massive acetabular (socket) destruction.
    • Threaded pins (Steinmann pins) are drilled into the sacrum/ilium to act as rebar. Hand-mixed cement is poured over them to create a new socket for a hip replacement cup.

Technical Specs: The Prophylactic Nail

  • The Femur:
    • Approach: Lateral incision proximal to Greater Trochanter.
    • Entry Point: Piriformis Fossa (Straight nail) or Tip of Trochanter (Curved nail).
    • Guide Wire: Passed across the lesion (carefully!). If the wire goes out the cortex, the nail will too.
    • Reaming: Gently ream to standard size. Warning: Reaming increases intramedullary pressure -> Fat Embolism. In patients with poor lung function (Lung Ca), consider unreamed nails or Venting.
    • Nail Insertion: Slide the titanium rod down.
    • Locking: Screws at top (into femoral neck/head) and bottom (into condyles).
  • The Humerus:
    • Approach: Anterolateral.
    • Risk: Radial Nerve palsy (spirals round the humerus).
    • Construct: Often a retrograde nail (from elbow up) or plate is preferred.
  1. Tumour Prosthesis:
    • Resecting the distal femur/proximal tibia and replacing it with a silver-coated mega-prosthesis.
    • High infection risk (Silver coating helps).

Karnofsky Performance Status (KPS)

Used to determine fitness for surgery.

ScoreStatus
100Normal, no complaints.
90Able to carry on normal activity.
80Normal activity with effort.
70Cares for self. Unable to carry on normal activity.
60Requires occasional assistance.
50Requires considerable assistance.
40Disabled. Requires special care.
30Severely disabled.
20Very sick. Admission necessary.
10Moribund.
0Dead.
  • Clinical Relevance: KPS <40 usually precludes major preventative surgery (High mortality).

Radiotherapy

  • External Beam (EBRT):
    • Post-Op: Mandatory after fixation to kill remaining tumour and prevent implant loosening.
    • Palliative: 8Gy in 1 Fraction (Standard) vs 20Gy in 5 Fractions. (Single fraction is as effective for pain).
  • Treatment: High dose Dexamethasone (16mg) + MRI Total Spine + Urgent Surgery/Radiotherapy.
  • Decision Framework: NOMS:
    • N (Neurologic): Low grade (Radiculopathy) vs High grade (Myelopathy).
    • O (Oncologic): Radio-sensitive (Myeloma/Lymphoma/Prostate) vs Radio-resistant (Renal/Melanoma).
      • Sensitive: Radiotherapy is primary.
      • Resistant: Surgery (Decompression) is primary.
    • M (Mechanical): Stable vs Unstable spine (SINS score).
      • Unstable: Needs Stabilization (Screws).
    • S (Systemic): Is the patient fit for major surgery?

Surgical Complications

8. Complications

Disease Progression

  1. Hypercalcaemia of Malignancy:
    • Pathophysiology: Systemic PTHrP release (Humoral) or Local Osteolysis.
    • Symptoms: "Bones, Stones, Moans, Groans" (Confusion, Abdominal pain, Polyuria).
    • ECG: Short QT interval. J waves.
    • Management Protocol:
      1. Hydration: Aggressive IV 0.9% Saline (3-4 Litres/24h) to restore GFR.
      2. Bisphosphonates: IV Zoledronic Acid 4mg (delayed effect - takes 48h).
      3. Steroids: Prednisolone (for Lymphoma/Myeloma).
      4. Calcitonin: Rapid but short-acting (tachyphylaxis).
    • Mechanisms:
      • Humoral Hypercalcaemia of Malignancy (HHM): 80% of cases (Squamous cell Ca - Lung/Head Neck). Tumour secretes PTHrP, which acts systemically on bone/kidney.
      • Local Osteolytic Hypercalcaemia (LOH): 20% of cases (Breast/Myeloma). Direct bone destruction releases filtered calcium.
      • Vitamin D Secreting: Lymphomas convert 25-OH-D to 1,25-OH-D.
  2. Malignant Spinal Cord Compression (MSCC):
    • Red Flag: New back pain in a cancer patient is MSCC until proven otherwise.
    • NOMS Framework: See above.
    • Treatment: Early decompression (<24h from onset of paraplegia) determines walking ability. Once established (>48h), paralysis is usually irreversible.

Surgical Complications

  • Bleeding: Especially Renal/Thyroid. Embolization is critical.
  • Infection: Immunocompromised patients (Chemo/Radio) have high infection risk.
  • Implant Failure: If the patient outlives the implant (and the bone doesn't heal because the tumour is there), the metal will eventually fatigue and snap.
9. Prognosis & Outcomes

Survival Scores

  • Tokuhashi Score: Predicts survival for spinal mets. Guides treatment (Aggressive surgery vs Palliative).
  • Katagiri Score: General bone mets survival.

Factors

  • Primary Type:
    • Good: Prostate, Breast, Thyroid (Years).
    • Bad: Lung, Gastric, Melanoma (Months).
  • Visceral Mets: Presence of liver/lung mets worsens prognosis significantly.
10. Evidence & Guidelines

Guidelines Summarized

BOAST 4: Metastatic Bone Disease (2021)

The British Orthopaedic Association Standards for Trauma (BOAST) mandates:

  1. MDT Approach: All patients must be discussed with the Oncology/Metastatic Bone Disease team.
  2. Timing: Surgery for impending/completed pathologic fractures should occur within 48 hours of admission.
  3. Implants: Long intramedullary nails spanning the whole bone should be used.
  4. Radiotherapy: All patients require Post-Operative Radiotherapy (unless prognosis <4 weeks) to prevent disease progression and implant failure.
  5. Embolization: Consider for renal/thyroid/myeloma.

NICE CG75: Metastatic Spinal Cord Compression (2008)

  1. Coordinator: Every hospital must have an MSCC Coordinator (24/7 availability).
  2. Imaging: MRI Whole Spine within 24 hours of suspicion.
  3. Steroids: 16mg Dexamethasone (+PPI) immediately on suspicion.
  4. Surgery: Definitive decompression/stabilization should generally happen before Radiotherapy (Patchell data).
  5. Mobilization: "Log roll" until spinal stability is confirmed.

The Multidisciplinary Team (MDT)

No single doctor manages bone mets.

  • Medical Oncologist: Prescribes Chemotherapy/Immunotherapy/Hormones.
  • Clinical Oncologist: Prescribes Radiotherapy.
  • Orthopaedic Surgeon: Fixes bones.
  • Palliative Care Physician: Complex pain management + End of life planning.
  • Radiologist: Interprets uncertain lesions/Biopsy.
  • Histopathologist: Determines tumour type.
  • Cancer Nurse Specialist (CNS): Patient advocate and point of contact.

Landmark Papers

  1. Mirels H (1989): "Metastatic Disease in Long Bones".
    • Findings: Developed the scoring system. Risk of fracture jumped from <5% (Score 7) to 33% (Score 9).
    • Impact: Defined the standard for prophylactic fixation.
  2. Patchell RA (2005): "Direct decompressive surgical resection... for spinal cord compression".
    • Design: RCT. Surgery + RT vs RT alone.
    • Result: Surgery group kept walking longer (122 vs 13 days). Lived longer (12 vs 9 months).
    • Impact: Shifted paradigm from RT-only to Surgery-First for walking patients.
  3. Rosen LS (2003): Zoledronic Acid Trials.
    • Result: Zometa reduced SREs in Breast/Myeloma/Prostate.
    • Impact: Standard of care.
  4. Stopeck AT (2010): Denosumab vs Zoledronic Acid.
    • Design: RCT in Breast Cancer.
    • Result: Denosumab superior in delaying first SRE (Not reached vs 26 months).
    • Note: Higher risk of Hypocalcaemia.

Spinal Instability Neoplastic Score (SINS)

Developed by the Spine Oncology Study Group (SOSG) to identify patients needing surgical stabilisation. Score range: 0-18.

  • 0-6: Stable. (Radiotherapy).
  • 7-12: Indeterminate. (Surgical consult).
  • 13-18: Unstable. (Surgery mandatory).
ComponentCategoryScore
LocationJunctional (Occiput-C2, C7-T2, T11-L1, L5-S1)3
Mobile Spine (C3-C6, L2-L4)2
Semi-rigid (T3-T10)1
Rigid (S2-S5)0
PainMechanical (Relieved by rest/loading pain)3
Occasional pain (Non-mechanical)1
Pain-free0
Bone LesionLytic2
Mixed (Lytic/Blastic)1
Blastic0
AlignmentSubluxation/Translation4
De Novo deformity (Kyphosis/Scoliosis)2
Normal alignment0
Vertebral Collapse>50% collapse3
<50% collapse2
No collapse but >50% body involved1
None0
Posterior ElementsBilateral involvement3
Unilateral involvement1
None0

Tokuhashi Score (Revised)

Predicts life expectancy to guide "En Bloc" resection vs Palliative stabilization. Total Score 0-15.

  • Score 12-15: Prognosis > 1 year. (Excisional Surgery).
  • Score 9-11: Prognosis > 6 months. (Palliative Surgery).
  • Score 0-8: Prognosis < 6 months. (Conservative/Minimally Invasive).
VariableCriteriaPoints
General ConditionKarnofsky 80-100%2
Karnofsky 50-70%1
Karnofsky 10-40%0
Extraspinal Bone MetsNone2
1-21
>= 30
Vertebral Mets12
21
>= 30
Visceral MetsNone2
Resectable1
Unresectable0
Primary SiteThyroid, Breast, Prostate, Carcinoid5
Kidney, Uterus3
Lung, Stomach, Bladder, Esophagus, Pancreas0
Spinal Cord PalsyNone2
Incomplete1
Complete0
11. Patient Explanation

What is a metastasis?

Cancer cells from your original tumour (like the breast or lung) have traveled through the blood and landed in the bone. Think of them like "seeds" landing in "soil". They grow there and start to weaken the bone structure.

Why surgery if it isn't broken?

The bone is currently like a hollowed-out tree branch. It is holding your weight, but only just. If you twist or stumble, it will snap (a "pathological fracture"). A broken thigh bone is very painful and requires a big emergency operation. We want to do a smaller, controlled operation now to put a metal rod inside the bone. This acts like "rebar" in concrete, taking the weight so the bone doesn't have to. You can walk on it immediately.

What about the pain?

The "gnawing" toothache pain comes from the pressure inside the bone. Radiotherapy (high-energy X-rays) is excellent at shrinking the tumour and stopping this pain. We usually give this after the surgery.

Why do you use cement?

In normal hip replacements, we often rely on your own bone growing onto the metal to hold it (Uncemented). But because the cancer has made your bone weak and it won't heal well, we can't wait for that. We use "Bone Cement" (a type of grout) to glue the metal in instantly. This means you can stand up on it as soon as you wake up from surgery.

Red Flags: When to call 999

Go to A&E immediately if:

  1. Leg Weakness: You suddenly cannot move your legs or they feel "heavy".
  2. Numbness: A band of numbness around your tummy or legs.
  3. Toilet Trouble: You wet yourself (incontinence) or cannot pee (retention). This is Spinal Cord Compression.
  4. Sudden Snap: A sharp crack in the thigh followed by inability to stand (Fracture).
  5. Confusion: Drowsiness, excessive thirst, and vomiting (High Calcium).

Psychological Support

A diagnosis of bone metastasis means the cancer is stage 4. This is devastating news.

  • Palliative Care: They are not just for "end of life". They are experts in pain control and quality of life. Get them involved early.
  • Support Groups: MacMillan, Roy Castle Lung Foundation, Prostate Cancer UK.

How do you decide if I need surgery?

We use a scoring system called the Mirels' Score. It looks at:

  1. Where is the hole? (Thigh bone is riskier than arm bone).
  2. Does it hurt? (Pain on walking is a bad sign).
  3. How big is it? (If it covers more than 2/3 of the bone, it will snap).
  4. What type is it? (Lytic holes result in fracture more often than Blastic ones). If your score is high (>8), safely fixing it now is better than waiting for a break.

What is the survival rate?

This depends entirely on the type of cancer.

  • Breast/Prostate: People live for many years (5-10+) with bone metastases. It is a chronic disease like diabetes.
  • Lung: The outlook is shorter (months), so we prioritize quick recovery and comfort. Regardless, fixing the bone doubles your chance of surviving the year compared to leaving it to break.

What is Radiotherapy?

It is like having a normal X-ray, but the beam is much stronger. You don't feel anything during the treatment.

  • Course: Usually just 1 visit (Single Fraction) or 5 visits over a week.
  • Side Effects:
    • Flare: Pain might get worse for 24-48h before getting better (Steroids help).
    • Tiredness: Fatigue is common.
    • Skin: Some redness (sunburn) over the area.

Mnemonics

  • Pb KTL ("Lead Kettle"): Sources of bone mets.
    • Prostate (Blastic)
    • breast (Mixed)
    • Kidney (Lytic)
    • Thyroid (Lytic)
    • Lung (Lytic)
  • Bones, Stones, Moans, Groans: Hypercalcaemia symptoms.
  • MUP: Metastasis of Unknown Primary.

Common Myths

  • Myth: "Surgery will spread the cancer."
    • Fact: The cancer has already spread to the bone. The surgery protects the bone. We use special techniques (cement) to kill local cells.
  • Myth: "I'm too old for surgery."
    • Fact: We operate on 90-year-olds regularly. The goal is quality of life (pain relief), not lifespan extension. Epidural anaesthesia makes it safer.
  • Myth: "Morphine will make me an addict."
    • Fact: When used for genuine severe pain, addiction is extremely rare. We monitor it carefully.
12. References
  1. Mirels H. Metastatic disease in long bones. A proposed scoring system for diagnosing impending pathologic fractures. Clin Orthop Relat Res. 1989;249:256-64. [PMID: 2684463]
  2. Patchell RA, et al. Direct decompressive surgical resection in the treatment of spinal cord compression caused by metastatic cancer: a randomised trial. Lancet. 2005;366(9486):643-8. [PMID: 16112300]
  3. Coleman RE. Clinical features, molecular mechanisms, and treatment of bone metastases. Clin Cancer Res. 2006;12(20):6243s-6249s. [PMID: 17062708]
  4. Stopeck AT, et al. Denosumab compared with zoledronic acid for the treatment of bone metastases in patients with advanced breast cancer: a randomized, double-blind study. J Clin Oncol. 2010;28(35):5132-9. [PMID: 21060033]
  5. Fisher CG, et al. A novel classification system for spinal instability in neoplastic disease: an evidence-based approach and expert consensus from the Spine Oncology Study Group. Spine. 2010;35(22):E1221-9. [PMID: 20938396] (SINS Score)
  6. Tokuhashi Y, et al. A revised scoring system for preoperative evaluation of metastatic spine tumor prognosis. Spine. 2005;30(19):2186-91. [PMID: 16205345]
  7. Harrington KD. Orthopedic management of extremity lesions. Clin Orthop Relat Res. 1995. [PMID: 7634615]
  8. Katagiri H, et al. Prognostic factors and a scoring system for patients with skeletal metastasis. J Bone Joint Surg Br. 2005. [PMID: 15736754]
  9. British Orthopaedic Association (BOA). BOAST 4: The Management of Metastatic Bone Disease. 2021.
  10. NICE CKS. Bone metastases. 2020.
  11. Roodman GD. Mechanisms of bone metastasis. N Engl J Med. 2004;350(16):1655-64. [PMID: 15084698]
  12. Berruti A, et al. Osteoblastic bone metastases in prostate cancer. Anticancer Res. 2012. [PMID: 22593457]
  13. Piccioli A, et al. Prophylactic nailing of impending pathological fractures of the femur. Injury. 2014. [PMID: 24268181]
13. Examination Focus

Common Exam Questions

  1. Q: What are the primary sources of bone metastases?
    • A: "Pb KTL" - Prostate, Breast, Kidney, Thyroid, Lung.
  2. Q: Which are Lytic and which are Blastic?
    • A: Prostate is Blastic. Lung, Renal, Thyroid are Lytic. Breast is Mixed.
  3. Q: What is Mirels' Score?
    • A: A scoring system to predict impending fracture risk based on Site, Pain, Size, and Type of lesion. Score >8 suggests prophylactic fixation.
  4. Q: Why embolize Renal Cell Carcinoma mets?
    • A: They are extremely vascular. Risk of massive intra-operative haemorrhage.

OSCE Station: The "Limping" Cancer Patient

  • Scenario: 65M with history of Lung Cancer. New thigh pain.
  • Task: Examine and manage.
  • Key Steps:
    1. Introduction: "I understand you have some new pain in your leg."
    2. History: "Is the pain worse at night?" (Yes). "Does it hurt to walk?" (Yes - Functional pain).
    3. Look: Wasting of quadriceps? (Disuse).
    4. Feel: Percuss the femur. If painful, stop. Do NOT do a straight leg raise (Risk of fracture).
    5. Move: Hip rotation (limited by pain).
    6. Neuro: Check L3/L4 (Knee jerk), L5 (Big toe extension).
    7. Investigation Plan:
      • "I would like an urgent full length femur X-ray." (Not just a hip X-ray - the met might be in the shaft).
      • "I will check his calcium (Bone profile)."
      • "I will calculate the Mirels' Score."
    8. Management Plan:
      • "If Mirels > 8, I will refer to Orthopaedics for a prophylactic IM Nail."
      • "If < 8, I will refer to Oncology for Radiotherapy."

Viva Questions

  1. Q: Why is the spine the most common site?
    • A: Batson's Plexus. This is a valveless venous network connecting the pelvic veins to the vertebral veins. Any increase in intra-abdominal pressure (coughing) shunts blood - and tumour cells - retrograde into the spine, bypassing the liver/lungs.
  2. Q: What is the risk of prophylactic nailing?
    • A: Fat Embolism Syndrome (Reaming pushes marrow into venous circulation). Tumour seeding (Nail drags cells distally).
  3. Q: Name 3 agents inhibiting osteoclasts.
    • A: Zoledronic Acid (Bisphosphonate), Denosumab (RANK-L inhibitor), Calcitonin.

(End of File)

Last updated: 2025-12-25

At a Glance

EvidenceHigh
Last Updated2025-12-25
Emergency Protocol

Red Flags

  • Back pain in a cancer patient -> Rule out Malignant Spinal Cord Compression (MSCC)
  • Severe thigh pain on weight bearing -> Impending Pathological Fracture (Mirels > 8)
  • Hypercalcaemia (Confusion, Vomiting, Polyuria) -> Oncological Emergency

Clinical Pearls

  • Proximal Long Bones (Femur/Humerus).
  • **"Prostate turns it White"**: On X-ray, Prostate cancer metastases look like "Cotton Wool" or "Snowballs" (Sclerotic). Lung cancer looks like "Moth holes" (Lytic).
  • **"The Cortical Rule"**: If a lytic lesion destroys more than 50% of the cortex (the hard outer shell) on any view, the bone has lost 90% of its torsional strength. It will snap if they twist on it.
  • **"The NNT"**: The Number Needed to Treat (NNT) for radiotherapy to achieve complete pain relief is about 3. For partial relief, it is nearly 1 in 1. It is incredibly effective.
  • Upregulates **RANK-L**.

Guidelines

  • NICE Guidelines
  • BTS Guidelines
  • RCUK Guidelines