Metastatic Bone Disease

On this page

Mets to Bones - Unwelcome Guests

  • Most common malignant bone tumors; significantly outnumber primary bone sarcomas.
  • Axial skeleton favored: Vertebrae, pelvis, ribs, skull, proximal femur/humerus.
  • Common Primaries (📌 "PB KTL"): Prostate, Breast, Kidney, Thyroid, Lung.
    • Osteoblastic: Prostate (classic), some Breast.
    • Osteolytic: Lung, Kidney, Thyroid, Myeloma.
    • Mixed: Breast.
  • Symptoms: Bone pain (often nocturnal, progressive), pathological fractures, hypercalcemia, neurological deficits (e.g., cord compression). Bone scan progression of metastatic bone disease

⭐ Lung, breast, and prostate cancers account for approximately 80% of all skeletal metastases.

Bone Under Siege - Lytic vs Blastic

  • Pathogenesis: Tumor cells secrete factors (cytokines, growth factors) altering bone remodeling.
  • Lytic Lesions (Osteolytic): "Bone breaking"
    • Mechanism: ↑ Osteoclast activity (e.g., PTHrP, RANKL).
    • Radiology: Radiolucent, "punched-out" defects.
    • Primaries: Multiple Myeloma, Lung, Kidney, Thyroid, Breast (lytic or mixed).
  • Blastic Lesions (Osteosclerotic): "Bone forming"
    • Mechanism: ↑ Osteoblast stimulation (e.g., Endothelin-1).
    • Radiology: Radiodense, sclerotic bone.
    • Primaries: Prostate (classic), Breast (mixed or blastic), Carcinoid.
  • Mixed Pattern: Common in Breast, Lung.

and blastic (white areas) bone metastases)

⭐ Prostate cancer is notorious for causing osteoblastic metastases, while Multiple Myeloma typically causes purely lytic lesions.

Red Flags Waving - Signs & Scans

  • Clinical Alarms:
    • Persistent bone pain (nocturnal/rest pain ↑).
    • Pathological fractures (minimal trauma).
    • Neurological deficits (spinal cord compression).
    • Hypercalcemia symptoms (confusion, constipation).
    • Known primary cancer history.
  • Imaging Arsenal:
    • X-ray: Initial; lytic (e.g., lung, kidney), blastic (e.g., prostate), mixed lesions. CT of metastatic bone disease in thoracic vertebrae
    • Bone Scan (Tc-99m): Sensitive for blastic activity; multiple lesions.
    • MRI: Marrow, soft tissue, cord compression.
    • CT: Bone detail, biopsy guidance.
    • PET-CT: Lytic lesions, staging, response.

⭐ Most common primary cancers metastasizing to bone: Prostate, Breast, Lung, Kidney, Thyroid. (📌 PB-KTL: "Painful Bones Kill Teens Like")

Risk Rating - Scores & Survival

  • Mirel's Score: Predicts pathological fracture risk in long bones.
    • Factors: Site, Pain, Lesion type (lytic/blastic), Size of lesion.
    • Score ≥ 9: Prophylactic fixation recommended.
    • Score ≤ 7: Non-operative management.
  • Tokuhashi Score (Revised): Estimates survival for spinal metastases.
    • Factors: KPS, extraspinal mets, vertebral mets, visceral mets, primary cancer, palsy.
    • Score 0-8: Poor prognosis (< 6 months survival).
    • Score 12-15: Better prognosis (> 12 months survival).

⭐ A Mirel's score of 8 is considered borderline, requiring individualized decision for fixation.

The Counterattack - Treatment Toolkit

Goals: Palliation, prevent/treat fractures (SREs), local control. Multimodal approach.

  • Systemic Therapy:
    • Bone-Targeted Agents: Bisphosphonates (e.g., Zoledronate), Denosumab (↓SREs).
    • Primary-Specific: Chemo, Hormonal, Targeted Rx.
  • Local Therapy:
    • Radiotherapy (RT): EBRT for pain (8 Gy single; 20 Gy/5fr; 30 Gy/10fr), local control.
    • Surgery: Pathological/impending # (Mirels score >8), spinal cord compression, instability, solitary lesion.
      • Procedures: Internal fixation, arthroplasty, excision.
  • Supportive Care:
    • Analgesia (WHO ladder), Rehabilitation.

X-ray: Femur with metastatic lesion and intramedullary nail

⭐ For painful bone metastases, a single 8 Gy fraction of radiotherapy offers pain relief comparable to multifraction regimens with greater convenience.

High‑Yield Points - ⚡ Biggest Takeaways

  • Most common primary cancers to bone: Prostate, Breast, Lung, Kidney, Thyroid (PB KTL).
  • Spine is the most frequent metastatic site, followed by pelvis and femur.
  • Pain (often nocturnal) and pathological fractures are key clinical features.
  • Lesions: Osteolytic (e.g., Lung, Kidney), Osteoblastic (e.g., Prostate), or Mixed (e.g., Breast).
  • Bone scan for screening; biopsy for definitive diagnosis. X-ray is initial imaging.
  • Management: Multimodal-radiotherapy for pain, bisphosphonates, surgical stabilization for fractures.
  • Mirels' score assesses impending fracture risk in long bones_

Practice Questions: Metastatic Bone Disease

Test your understanding with these related questions

An elderly woman presented with confusion, thirst, and abdominal pain symptoms. On examination, she had pallor and thoracic spine tenderness. X-ray spine showed osteolytic lesions. Her lab investigations showed the following findings. What is the most likely diagnosis? - Hb - 6.9 g/dl

1 of 5

Flashcards: Metastatic Bone Disease

1/7

If the size of the lesion is >2/3, it is given a score of _____ according to Mirel's criteria

TAP TO REVEAL ANSWER

If the size of the lesion is >2/3, it is given a score of _____ according to Mirel's criteria

3

browseSpaceflip

Enjoying this lesson?

Get full access to all lessons, practice questions, and more.

Start Your Free Trial