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Updated: Jan 1 2022

Metastatic Cancer to Bone

  • Introduction
    • Metastatic cancer is the most common reason for a destructive bone lesion in adults
      • bone is the third most common site for metastatic disease (behind lung and liver)
      • carcinomas that commonly spread to bone include
        • breast
        • lung
        • thyroid
        • renal
        • prostate
    • Metastatic hypercalcemia
      • a medical emergency
      • treat with hydration and loop diuretics
  • epidemiology
    • Age & location
      • metastatic bone lesions are usually found in older patients (> 40 yrs)
      • common sites of metastatic lesions include
        • axial skeleton (vertebral bodies, pelvis, ribs)
        • proximal limb girdle
          • proximal femur is most common site of fracture secondary to metastatic bone lesions
  • etiology
    • Mechanism
      • mechanism of bone destruction (osteolysis)
        • metastatic bone destruction (causing osteolytic bone lesions) is caused by tumor induced activation of osteoclasts
          • occurs through the RANK, RANK ligand (RANKL), osteoprotegrin pathway
      • mechanism of tumor metastasis
        • metastasis requires
          • tumor cell intravasation
          • avoidance of immune surveillance
          • target tissue localization
          • extravasation into the target tissue
          • induction of angiogenesis
          • genomic instability
          • decreased apoptosis
  • Presentation
    • Symptoms
      • pain
        • may be mechanical pain due to bone destruction or tumorigenic pain which often occurs at night
      • pathologic fracture
        • occurs at presentation in 8-30% of patients with metastatic disease
      • malignant hypercalcemia
        • confusion
        • polyuria & polydipsia
        • nausea/vomiting
        • dehydration
    • Physical exam
      • metastatic hypercalcemia
        • muscle weakness
  • Imaging
    • Radiographic characteristics
      • purly lytic or mixed lytic/blastic lesions
        • 30% of lung CA is blastic
        • 60% of breast CA is blastic
        • 90% of prostate CA is blastic
      • cortical metastasis are common in lung cancer
      • lesions distal to elbow and knee are usually from lung or renal primary
  • studies
    • Workup for older patient with single bone lesion and unknown primary includes
      • imaging
        • plain radiographs
        • CT of chest / abdomen / pelvis
        • technetium bone scan
      • labs
        • CBC with differential
        • ESR
        • basic metabolic panel
        • LFTs, Ca, Phos, alkaline phosphataseserum and urine immunoelectrophoresis (SPEP, UPEP)
      • biopsy
        • in patients where a primary carcinoma is not identified, obtaining a biopsy is necessary to rule out a primary bone lesion
    • Histology
      • Characteristic findings of metastatic lesions
        • epithelial cells in clumps or glands in a fibrous stroma
      • Immunohistochemical stains positive
        • Keratin
        • CK7 (breast and lung cancer)
        • TTF1 (lung cancer)
  • Treatment
    • Nonoperative
      • bisphosphonate therapy
        • IV pamidronate prevents osteoclatic bone destruction
      • dexamethasone
        • prevents progressive neurologic injury with spinal cord compression
      • radiation alone
        • indications
          • indicated in radiosenstive tumors such as breast cancer, prostate cancer, multiple myeloma and lymphoma
          • indicated to shrink mets that are causing spinal cord compression
    • Operative
      • prophylactic IM nailing or arthroplasty with adjuvent radiation
        • indications
          • impending fx that meets criteria
      • spinal neurologic decompression, stabilization, with postoperative radiation therapy
        • indications
          • metastatic lesions to the spine showing compression of neural elements and progressive neurologic deficits that are decreasing the quality of life in patient with life expectancy of greater than six months
  • Differentials & Groups
    • Malignant lesion in older patient(1)
      Multiple lesion in older patient(1)
      Epithelial glands on histology
      Benefits from Bisphonate therapy
      Treatment is wide resection and radiation(2)
      Metastatic bone disease
      Myeloma
      Lymphoma
      Chondrosarcoma
      MFH / fibrosarcoma
      Secondary sarcoma
      Pagets disease
      Fibrous dysplasia
      Synovial sarcoma
      Hyperparathyroidism
      Gomus tumor
      Soft tissue sarcomas(3)
      ASSUMPTIONS: (1) Older patient is > 40 yrs; (2) assuming no impending fracture (3) High-grade soft tissue sarcomas includes angiosarcoma, synovial sarcoma, liposarcoma, desmoid tumor, MFH/fibrosarcoma: exception is rhabdomysarcoma which is treated with chemotherapy and wide resection
    • Location
      Xray
      Xray
      CT
      B. Scan
      MRI
      MRI
      Histo(1)
      Case Aprox femur
      Case Bpelvis
      Case Chand (thyroid CA)
      Case Dhand (lung CA)
      Case Efemur (lung CA)
      Case Fpelvis
      Case Grenal CA (angio)
  • Prognosis
    • Median survival in patients with metastatic bone disease
      • thyroid: 48 months
      • prostate: 40 months
      • breast: 24 months
      • kidney: variable depending on medical condition but may be as short as 6 months
      • lung: 6 months
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