High Yield Overview

Metastatic Bone Disease

Most Common Bone Malignancy

5 Common PrimariesBPLTK

Fix ItMirels above 8

Red Marrow SitesAxial

EmbolizeKidney/Thyroid

PalliationGoal

Common Primary Tumors

Breast

PatternMost common in women. Mixed/lytic

TreatmentResponsive to hormone/chemo. Years survival

Prostate

PatternMost common in men. BLASTIC

TreatmentOften indolent. Years survival

Lung

PatternUsually lytic. Poor prognosis

TreatmentMonths survival. Rarely fix if poor status

Kidney

PatternLytic. VERY VASCULAR

TreatmentEmbolize pre-op. Months-years survival

Thyroid

PatternLytic. VERY VASCULAR

TreatmentEmbolize pre-op. Good prognosis if differentiated

Critical Must-Knows

BPLTK Primaries: Breast (female), Prostate (male), Lung (poor prognosis), Thyroid, Kidney.
Mirels Score: 4 parameters (Site, Pain, Lesion, Size) - above 8 needs prophylactic fixation.
Blastic Metastases: Prostate (most), breast (treated), small cell lung.
Lytic Metastases: Kidney, thyroid, lung - structurally weaker.
Vascular Tumors: Kidney and thyroid - MUST embolize before surgery.

Examiner's Pearls

"
BPLTK for common primaries
"
Mirels above 8 = prophylactic fixation
"
Kidney and thyroid are VASCULAR - embolize
"
Blastic = prostate; Lytic = kidney
"
Surgical goal is PALLIATION, not cure

Clinical Imaging

Imaging Gallery

Coronal and axial fused 18F-FDG PET/CT images. (a) Initial diagnosis of myeloma, multiple foci of metabolic activity. (b) Extension of lesions and new lesions following relapse. (c) Complete metabolic — Coronal and axial fused 18F-FDG PET/CT images. (a) Initial diagnosis of myeloma, multiple foci of metabolic activity. (b) Extension of lesions and newCredit: Ebana H et al. via Case Rep Hematol via Open-i (NIH) (Open Access (CC BY))

Bone marrow and specimen from the sacral mass. ((a), (b)) Immunostaining for CD138 in the bone marrow clot section showing microcluster infiltration of plasma cells (x40, x200). (c) Bone marrow aspira — Bone marrow and specimen from the sacral mass. ((a), (b)) Immunostaining for CD138 in the bone marrow clot section showing microcluster infiltration oCredit: Ebana H et al. via Case Rep Hematol via Open-i (NIH) (Open Access (CC BY))

MRI had appearances suggestive of an infectious spondylitis such as TB spondylitis associated with a pathologic fracture rather than a metastatic bone tumor (arrow), because vertebral involvement by m — MRI had appearances suggestive of an infectious spondylitis such as TB spondylitis associated with a pathologic fracture rather than a metastatic boneCredit: Kim DH et al. via Ann Rehabil Med via Open-i (NIH) (Open Access (CC BY))

X-ray showed only L4 compression fracture, with preservation of the pedicles (arrow). (A) Anterior-posterior view. (B) Lateral view.Credit: Kim DH et al. via Ann Rehabil Med via Open-i (NIH) (Open Access (CC BY))

Mirels Score is the Key Exam Concept

Mirels Score predicts pathological fracture risk.

4 Parameters: Site (upper/lower/peritrochanteric), Pain (mild/moderate/functional), Lesion (blastic/mixed/lytic), Size (under 1/3, 1/3-2/3, over 2/3 cortex).
Score 1-3 for each (total range 4-12).
Score above 8: Greater than 33% fracture risk → PROPHYLACTIC FIXATION indicated.
Score 9+: Greater than 50% fracture risk → DEFINITE fixation.
Peritrochanteric location and lytic lesions score highest risk.

Mirels Scoring System

Parameter	Score 1	Score 2
Upper limb	Lower limb	Peritrochanteric
Mild (not affected by activity)	Moderate (some relief with rest)	Functional (pain with weight-bearing)
Blastic (sclerotic)	Mixed	Lytic (destructive)
Under 1/3 diameter	1/3 to 2/3 diameter	Over 2/3 diameter

Mirels 7 or Under

Mirels 8

Mirels 9+

Vascular Tumors

At a Glance

Metastatic bone disease is the most common malignancy affecting bone, far exceeding primary bone tumors. The BPLTK primaries (Breast, Prostate, Lung, Thyroid, Kidney) account for most cases, with metastases preferentially affecting the axial skeleton following red marrow distribution. The Mirels scoring system predicts pathological fracture risk using 4 parameters (Site, Pain, Lesion type, Size)—scores greater than 8 indicate prophylactic fixation due to greater than 33% fracture risk. Blastic lesions suggest prostate (most common), while lytic lesions (kidney, thyroid, lung) are structurally weaker. Kidney and thyroid metastases are highly vascular and require preoperative embolization. Management is palliative with durable constructs allowing immediate weight-bearing.

Mnemonic

Common Primaries - BPLTK

Breast

Most common female, mixed/lytic

Prostate

Most common male, BLASTIC

Lung

Poor prognosis, lytic

Thyroid

Vascular - embolize

Kidney

Vascular - embolize

Memory Hook:BPLTK (Bad Places Leak To Kidneys) - the 5 common primaries that metastasize to bone.

Mnemonic

Mirels Score - SPLS

Site

Upper (1) / Lower (2) / Peritroch (3)

Pain

Mild (1) / Moderate (2) / Functional (3)

Lesion

Blastic (1) / Mixed (2) / Lytic (3)

Size

Under 1/3 (1) / 1/3-2/3 (2) / Over 2/3 (3)

Memory Hook:SPLS - Site, Pain, Lesion, Size. Above 8 = Fix, above 9 = Definitely fix.

Mnemonic

Blastic vs Lytic - PBS

Prostate

BLASTIC (most common blastic)

Breast

Often blastic when treated

Small Cell

Small cell lung can be blastic

Memory Hook:PBS (Prostate, Breast, Small cell) make bone STRONGER (blastic). Everything else is LYTIC and weak.

Mnemonic

Vascular Metastases - TK

Thyroid

Very vascular - EMBOLIZE

Kidney

Very vascular - EMBOLIZE

Memory Hook:TK (Total Knockout) - Thyroid and Kidney will knock you out with blood loss. Embolize 24-48h before surgery.

Overview and Epidemiology

Metastatic bone disease is the most common malignancy affecting bone, far exceeding primary bone tumors in frequency.

Epidemiology

Incidence: 25-30x more common than primary bone tumors
Prevalence: Found at autopsy in 70-85% of patients with breast/prostate cancer
Age: Typically middle-aged to elderly (reflecting primary cancer demographics)
Impact: 350,000-400,000 people living with bone metastases in USA

Common Primary Tumors (BPLTK)

Breast: Most common source overall and in women
Prostate: Most common source in men
Lung: Third most common; poor prognosis
Thyroid: Differentiated carcinoma has better prognosis
Kidney: Renal cell carcinoma; very vascular

Less Common Primaries

Gastrointestinal (colon, stomach)
Bladder
Melanoma
Unknown primary (10-15% of cases)

Distribution (Red Marrow Distribution)

Spine: 70% - most common site (thoracic greater than lumbar greater than cervical)
Pelvis: 40%
Proximal Femur: 25%
Ribs: 25%
Skull: 15%
Proximal Humerus: 15%

Pathophysiology

Mechanisms of Bone Metastasis

Metastatic Cascade:

Primary Tumor Growth: Cancer cells proliferate in organ of origin
Local Invasion: Tumor penetrates basement membrane
Intravasation: Entry into bloodstream or lymphatics
Circulation: Survival in circulation (most cells die)
Extravasation: Exit from vessels at distant site
Colonization: Establish growth in bone microenvironment

Why Bone?

Hematogenous Spread: Most common route to bone
Batson's Venous Plexus: Valveless vertebral venous system allows retrograde flow
- Explains predilection for spine and axial skeleton
- Low-pressure system facilitates tumor cell lodging
Red Marrow Distribution: Sites with active hematopoiesis
- Rich blood supply
- Growth factors present
- Supportive microenvironment

The Vicious Cycle

Seed and Soil Hypothesis (Paget 1889): Cancer cells (seed) preferentially grow in bone microenvironment (soil)

The Cycle:

Tumor cells arrive in bone marrow
Tumor cells secrete factors (PTHrP, IL-6, TNF) → stimulate osteoclasts
Osteoclasts resorb bone → release growth factors (TGF-β, IGF, BMPs)
Growth factors stimulate tumor → more factor secretion
Cycle perpetuates → progressive bone destruction

Lytic vs Blastic Metastases

Lytic Lesions (Bone Destruction):

Kidney, thyroid, lung
Osteoclast activation dominant
Structurally weak bone
High fracture risk
Mechanisms: PTHrP, IL-1, IL-6, TNF-α

Blastic Lesions (Bone Formation):

Prostate (most), treated breast, small cell lung
Osteoblast activation dominant
Dense but disorganized bone (structurally weak)
Lower fracture risk
Mechanisms: Endothelin-1, BMPs, Wnt signaling

Mixed Lesions:

Breast (untreated), GI cancers
Both processes active

Role of RANK/RANKL Pathway

RANK: Receptor on osteoclast precursors
RANKL: Ligand secreted by osteoblasts and tumor cells
RANKL binding to RANK: Osteoclast activation and differentiation
OPG (osteoprotegerin): Decoy receptor, inhibits RANKL
Therapeutic target: Denosumab (RANKL inhibitor)

Clinical Features

History

Known Cancer: 85% have known primary at presentation
Unknown Primary: 15% bone metastasis is first presentation of cancer
Pain: Most common symptom
- Night pain (classic)
- Activity-related (mechanical instability)
- Rest pain (tumor growth)
Pathological Fracture: May be presenting feature
Neurological: Spinal cord compression (weakness, sensory changes, bladder/bowel)
Constitutional: Weight loss, fatigue, anorexia

Physical Examination

Examination Approach

Local Assessment
- Point tenderness over lesion
- Palpable mass (large lesions)
- Surrounding soft tissue swelling
Fracture Assessment
- Deformity, shortening
- Inability to weight-bear
- Crepitus (do not elicit if suspected)
Neurological Assessment (Spine)
- Motor: Power in myotomes
- Sensory: Dermatomal distribution
- Reflexes: Hyperreflexia (UMN) or hyporeflexia
- Bladder/bowel function
- Rectal tone, perianal sensation
Systemic Assessment
- Breast examination
- Prostate examination (DRE)
- Thyroid palpation
- Lymphadenopathy
- Abdominal masses
- General condition, performance status

Red Flags for Cord Compression

New back pain in cancer patient
Bilateral leg symptoms
Bladder/bowel dysfunction
Progressive weakness
Sensory level

Spinal Cord Compression - Oncological Emergency

Metastatic spinal cord compression is an EMERGENCY. Early recognition critical as neurological recovery correlates with pre-treatment function. MRI whole spine urgently. High-dose dexamethasone, urgent oncology/spinal referral for decompression/radiation.

Investigations

Imaging

Plain Radiographs:

First-line investigation
Lytic (dark, destructive) vs Blastic (white, sclerotic) vs Mixed
Need 30-50% cortical destruction to be visible
Assess fracture risk, deformity

CT Scan:

Better cortical assessment than X-ray
Quantify bone destruction
CT chest/abdomen/pelvis for staging
CT-guided biopsy planning

MRI:

Most sensitive for marrow involvement
Essential for spinal metastases
Assesses soft tissue extension
Whole spine MRI if cord compression suspected

Bone Scintigraphy (Bone Scan):

Whole-body screening
Highly sensitive but low specificity
May miss pure lytic lesions (kidney, myeloma)
Superscan = widespread metastases

PET-CT:

Increasingly used for staging
Assesses metabolic activity
Helps identify unknown primary
Monitors treatment response

Laboratory Investigations

Full Blood Count: Anaemia, pancytopenia (marrow infiltration)
Biochemistry: Calcium (hypercalcemia), ALP (elevated), LDH
Tumor Markers: PSA (prostate), CEA (GI, breast), AFP (germ cell), thyroglobulin
Serum/Urine Protein Electrophoresis: Exclude myeloma
Iron Studies: Chronic disease pattern

Biopsy

Indications:

Unknown primary tumor
Solitary lesion (could be primary bone tumor)
Atypical presentation
Clinical doubt about diagnosis

Technique:

Image-guided core needle biopsy (preferred)
Align biopsy tract with potential surgical approach
Tissue for histology, immunohistochemistry, molecular studies

Exam Pearl

A solitary bone lesion in a patient with known cancer is NOT always metastatic. 10% of solitary lesions in cancer patients are primary bone tumors or benign. Biopsy if any doubt.

Management

Management Principles

Goals of Treatment:

Palliation - NOT cure
Pain relief
Restore/maintain function
Prevent pathological fracture
Improve quality of life
Durable solution (patient may outlive implant)

Multidisciplinary Approach:

Medical oncology
Radiation oncology
Orthopaedic surgery
Palliative care
Pain management
Physiotherapy

Factors Affecting Treatment:

Primary tumor type and responsiveness
Expected survival
Performance status
Extent of metastatic disease
Fracture risk (Mirels score)
Patient wishes

Complications

Skeletal-Related Events (SREs)

Definition: Major complications from bone metastases requiring intervention

Types of SREs:

Pathological Fracture: Most common SRE
Spinal Cord Compression: Neurological emergency
Bone Pain Requiring Radiation: Severe uncontrolled pain
Hypercalcemia of Malignancy: Metabolic emergency
Surgery to Bone: Stabilization or reconstruction

Pathological Fracture

Incidence: 10-30% of patients with bone metastases

Risk Factors:

Lytic lesions (higher risk than blastic)
Large lesion size (greater than 2/3 cortex)
Peritrochanteric location
Weight-bearing bones
Mirels score above 8

Management:

Urgent surgical stabilization
Durable construct allowing immediate weight-bearing
Post-operative radiation
Worse outcomes than prophylactic fixation

Spinal Cord Compression

Oncological Emergency - Time-sensitive intervention

Incidence: 5-10% of cancer patients

Clinical Features:

Back pain (95% - often first symptom)
Motor weakness (75%)
Sensory changes (50%)
Bladder/bowel dysfunction (50%)
Ambulatory status predicts outcome

Management:

High-dose dexamethasone (10mg IV, then 16mg daily)
Urgent MRI whole spine
Neurosurgical/spinal consult
Decompression + stabilization vs radiation
HOURS matter - neurological recovery correlates with pre-treatment function

Prognostic Factors:

Pre-treatment ambulatory status (most important)
Time to develop motor deficit
Extent of cord compression
Primary tumor type

Hypercalcemia of Malignancy

Metabolic Emergency

Mechanism:

Osteoclastic bone resorption (lytic metastases)
PTHrP secretion by tumor (humoral)
Vitamin D production (lymphoma)

Clinical Features:

Confusion, lethargy
Nausea, vomiting, constipation
Polyuria, polydipsia
Dehydration
Cardiac arrhythmias

Management:

IV hydration (4-6L normal saline)
Bisphosphonates (zoledronic acid)
Calcitonin (rapid but short-lived effect)
Denosumab if bisphosphonates fail
Treat underlying cancer

Bone Pain

Impact:

Occurs in 75% of patients with bone metastases
Severe impact on quality of life
Limits mobility and function

Mechanisms:

Periosteal stretching
Microfractures
Tumor growth
Inflammatory mediators
Nerve compression

Management:

WHO pain ladder (simple analgesics → opioids)
Radiation therapy (80% response rate)
Bisphosphonates/denosumab
Interventional pain management
Neurolytic procedures for refractory pain

Surgical Complications

Intraoperative:

Massive hemorrhage (especially kidney/thyroid)
Cement extravasation
Neurovascular injury
Fat embolism

Post-operative:

Wound complications (15-20%)
Infection (5-10% - higher than non-cancer surgery)
Implant failure
Local tumor progression
DVT/PE (high risk population)

Minimizing Complications:

Preoperative embolization (vascular tumors)
Meticulous surgical technique
Adequate bone cement use
Post-operative radiation
DVT prophylaxis
Multidisciplinary approach

Long-term Complications

Radiation Effects:

Impaired fracture healing
Radiation-induced fractures (rare)
Soft tissue fibrosis

Bone-Targeted Agent Toxicity:

Osteonecrosis of jaw (ONJ): 1-2% risk
Atypical femur fractures (rare)
Renal impairment (bisphosphonates)

Disease Progression:

Local recurrence despite treatment
New skeletal lesions
Visceral metastases
Declining performance status

Special Considerations

Unknown Primary

10-15% of bone metastases have no known primary
Workup: CT CAP, PET, tumor markers, serum/urine electrophoresis
Biopsy essential for diagnosis and treatment planning
Immunohistochemistry directs investigation

Solitary Metastasis

May represent oligometastatic disease
Consider aggressive local treatment
Wide resection + adjuvant therapy in selected cases
Better prognosis than polymetastatic disease

Renal Cell Carcinoma (Special Case)

Very vascular - MUST embolize
May be radiosensitive (modern targeted therapy)
Solitary metastasis: Consider nephrectomy + metastasectomy
Targeted therapy (TKIs, immunotherapy) have improved outcomes

Pathological Fracture vs Impending Fracture

Actual fracture: Fix urgently, control pain
Impending fracture: Elective prophylactic fixation
Better outcomes with prophylactic surgery than fracture fixation

Evidence Base

Level IV

📚 Mirels H - Metastatic Disease in Long Bones

Key Findings:

Developed scoring system for pathological fracture risk
4 parameters: Site, Pain, Lesion, Size
Score above 8 correlates with 33% fracture risk
Widely adopted as clinical decision-making tool

Clinical Implication: Mirels score above 8 indicates prophylactic fixation. Remains standard for fracture risk assessment despite limitations.

Source: Clinical Orthopaedics and Related Research, 1989

Level IV

📚 Damron et al - Critical Evaluation of Mirels

Key Findings:

Validated Mirels criteria
Sensitivity 91%, specificity 35%
High sensitivity - good for ruling out fracture risk
Low specificity - over-predicts fracture risk

Clinical Implication: Mirels score is sensitive but may over-treat. Useful for identifying low-risk patients who do not need surgery.

Source: Clinical Orthopaedics and Related Research, 2003

Level V (Consensus)

📚 Bone Metastases Consensus Statement

Key Findings:

Multidisciplinary approach essential
Prophylactic fixation better outcomes than fracture fixation
Bisphosphonates/denosumab reduce skeletal events
Radiation improves local control

Clinical Implication: Integrated MDT approach with medical, radiation, and surgical oncology optimizes patient outcomes.

Source: Journal of Bone and Joint Surgery Am, 2018

Level II (Systematic Review)

📚 Preoperative Embolization - Systematic Review

Key Findings:

Embolization reduces blood loss by 50-80%
Kidney and thyroid metastases most vascular
Optimal timing 24-48 hours before surgery
Low complication rate in experienced hands

Clinical Implication: Preoperative embolization is MANDATORY for renal and thyroid metastases to reduce surgical blood loss.

Source: Journal of Vascular and Interventional Radiology, 2015

Level I (RCT)

📚 Denosumab vs Zoledronic Acid

Key Findings:

Denosumab superior to zoledronic acid for preventing skeletal events
18% relative risk reduction
Similar rates of ONJ
Subcutaneous administration more convenient

Clinical Implication: Denosumab is preferred bone-targeted agent for preventing skeletal-related events in metastatic bone disease.

Source: Lancet, 2011

Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Impending Pathological Fracture

EXAMINER

"A 68-year-old woman with breast cancer presents with painful right thigh. X-ray shows a large lytic lesion in the proximal femur involving 60% of the cortex. She has functional pain on weight-bearing. Mirels score is 9."

EXCEPTIONAL ANSWER

Diagnosis: This is a metastatic breast cancer lesion with high risk of pathological fracture (Mirels score 9). The Mirels parameters are: Site (peritrochanteric = 3), Pain (functional = 3), Lesion (lytic = 3), Size (over 2/3 diameter would be 3, but she has 60% which is 2/3 so = 2).

Mirels Score Calculation:

Site: Lower limb = 2 (or peritrochanteric = 3)
Pain: Functional = 3
Lesion: Lytic = 3
Size: 60% = 1/3-2/3 = 2
Total = 9-10 (above 8 = prophylactic fixation indicated)

Management:

Staging: CT CAP, bone scan if not recent
MDT Discussion: Oncology, radiation, surgical planning
Surgical Options:
If femoral head/neck spared: Cephalomedullary nail (long, protects whole femur)
If head/neck involved: Endoprosthetic replacement (long-stem cemented prosthesis)
Post-op: Radiation to lesion for local control
Systemic: Continue oncological management

Key Principles: Goal is palliation - pain relief, immediate weight-bearing, durable construct. Prophylactic fixation has better outcomes than waiting for fracture.

KEY POINTS TO SCORE

Mirels above 8 indicates prophylactic fixation

Breast cancer responsive to treatment - good candidate for surgery

Cephalomedullary nail if head/neck spared, prosthesis if involved

Post-operative radiation for local control

Goal is palliation with durable construct

COMMON TRAPS

✗Waiting for actual fracture (worse outcomes)

✗Short nail not protecting entire bone

✗Forgetting post-operative radiation

✗Not considering MDT approach

LIKELY FOLLOW-UPS

"What if this was a renal cell carcinoma?"

"How do you calculate the Mirels score?"

"What are the surgical options for proximal femur?"

VIVA SCENARIOStandard

Vascular Metastasis

EXAMINER

"A 72-year-old man with known renal cell carcinoma has a painful proximal humerus lesion. X-ray shows a large lytic lesion. You're planning surgery. What additional steps are needed?"

EXCEPTIONAL ANSWER

Key Issue: Renal cell carcinoma is HIGHLY VASCULAR. Without preoperative embolization, there is risk of massive intraoperative hemorrhage.

Preoperative Preparation:

EMBOLIZATION - MANDATORY for RCC
Timing: 24-48 hours before surgery
Interventional radiology referral
Selective embolization of feeding vessels
Blood bank: Cross-match adequate blood products

Staging Workup:

CT CAP - assess extent of disease, other metastases
Is primary tumor controlled? Nephrectomy status?
PET scan if staging unclear
Oncology input - targeted therapy options (TKIs, immunotherapy)

Surgical Planning:

Options: Endoprosthetic replacement vs reconstruction nail
Depends on extent of bone destruction
If large defect: Endoprosthetic reconstruction
If small lesion: Nail with cement augmentation
Cell saver NOT recommended (tumor cells)

Post-operative:

Radiation therapy
Systemic therapy as per oncology
Surveillance imaging

KEY POINTS TO SCORE

Renal cell carcinoma is VERY VASCULAR - MUST embolize

Embolization 24-48 hours before surgery

Reduces blood loss by 50-80%

Also applies to thyroid metastases

Cell saver contraindicated (tumor cells)

COMMON TRAPS

✗Operating without embolization (massive hemorrhage)

✗Embolizing too early (revascularization)

✗Using cell saver in malignancy

✗Forgetting to stage the patient

LIKELY FOLLOW-UPS

"What other tumors require embolization?"

"What is the timing for embolization?"

"What are the complications of embolization?"

VIVA SCENARIOStandard

Unknown Primary with Bone Metastasis

EXAMINER

"A 65-year-old man presents with back pain and pathological fracture of L3. No cancer history. X-ray shows lytic destruction. How would you investigate and manage?"

EXCEPTIONAL ANSWER

Diagnosis: This is a pathological fracture from presumed metastatic disease with unknown primary. Approximately 10-15% of bone metastases present without known primary.

Urgent Assessment:

Neurological status: Is there cord compression?
If neurological deficit: EMERGENCY MRI, high-dose dexamethasone, urgent decompression
If neurologically intact: Can proceed with workup

Investigations to Find Primary:

History and Exam: Smoking, weight loss, GI symptoms, breast exam, DRE
Bloods: PSA (prostate), CEA (GI), AFP (germ cell), thyroglobulin, serum/urine electrophoresis (myeloma)
CT CAP: Chest, abdomen, pelvis - most common primaries
PET-CT: If CT negative - highly sensitive for occult primary
Bone scan: Assess for other skeletal metastases
Biopsy: CT-guided core biopsy of vertebral lesion

Biopsy Importance:

Guides systemic treatment
Could be lymphoma (non-surgical management)
Could be myeloma (different workup)
Immunohistochemistry helps identify primary

Management:

If stable and awaiting diagnosis: Bracing, analgesia
If unstable or neurological compromise: Surgical stabilization
Once primary identified: Systemic therapy, radiation, MDT approach

KEY POINTS TO SCORE

10-15% of bone metastases have unknown primary

Systematic workup: PSA, CEA, CT CAP, PET, biopsy

Biopsy essential before definitive treatment

Consider myeloma, lymphoma in differential

Neurological status determines urgency

COMMON TRAPS

✗Assuming it's metastatic without biopsy

✗Missing cord compression

✗Not performing systematic primary workup

✗Operating before establishing diagnosis (unless emergency)

LIKELY FOLLOW-UPS

"What tumor markers would you check?"

"What if biopsy shows lymphoma?"

"How would management differ for myeloma?"

MCQ Practice Points

Exam Pearl

Q: Which primary cancers most commonly metastasize to bone? A: Breast, prostate, lung, thyroid, and kidney (mnemonic: "BLT with a Kosher Pickle"). These five primaries account for over 80% of skeletal metastases. Breast and prostate are the most common sources overall.

Exam Pearl

Q: What Mirels score indicates prophylactic fixation is recommended? A: Score of 9 or greater (out of 12) indicates prophylactic fixation. Mirels scoring assesses site, pain, lesion type (lytic/blastic/mixed), and size. A score of 8 has approximately 15% fracture risk, while 9 or above has greater than 33% risk.

Exam Pearl

Q: Which primary tumors typically produce osteoblastic (sclerotic) metastases? A: Prostate and breast cancer. Prostate is classically blastic (98% blastic), while breast can be lytic, blastic, or mixed. Lung, thyroid, and renal metastases are typically lytic. Multiple myeloma is also purely lytic.

Exam Pearl

Q: What is the mechanism of action of denosumab in treating bone metastases? A: RANKL inhibitor (monoclonal antibody). By blocking RANKL, denosumab prevents osteoclast activation and bone resorption. Unlike bisphosphonates, it is not renally excreted so is safer in renal impairment.

Australian Context

Metastatic bone disease management in Australia follows a multidisciplinary team approach as standard at major cancer centers. Bone-targeted agents (bisphosphonates, denosumab) are PBS-listed for bone metastases. Most bone metastasis surgery is performed at tertiary centers with access to interventional radiology for preoperative embolization.

The Cancer Council Australia (COSA) guidelines emphasize early orthopaedic referral for high-risk lesions and integration of palliative care. PET-CT is increasingly used for staging. Indigenous Australians may have higher rates of late presentation due to limited access to specialist services in remote areas, making cultural considerations important in end-of-life care planning.