Osteosarcoma

1. Epidemiology
   1. Bone Sarcoma is rare
      1. Incidence: 2500 U.S. cases diagnosed per year
   2. Osteosarcoma is most common Bone Sarcoma
      1. Third most common childhood malignancy
   3. Ages affected: 5-30 years (most common ages 10-20)
2. Pathophysiology
   1. High-grade mesenchymal tumor
   2. Most common sites of involvement
      1. Distal femur
      2. Proximal tibia
      3. Proximal Humerus
   3. Most common sites of metastasis
      1. Skip lesions
         1. Regional metastases form via satellite growth
         2. May be transarticular or intraosseous
      2. Systemic metastases
         1. Lungs (most common)
         2. Distant bone (occurs after lung metastases)
   4. Growth
      1. Grows outward radially forming ball-like mass
      2. Reactive Zone (Pseudocapsule composed of muscle)
         1. Forms when Tumor extends beyond bone cortex
         2. Compresses surrounding muscles
         3. Muscle appears as pseudocapsule to tumor
      3. Satellites (Tumor extension beyond pseudocapsule)
         1. Small tumor Nodules form outside pseudocapsule
         2. Microextension of tumor (satellites)
3. Symptoms
   1. Dull aching unilateral bone pain for several months
      1. Patient often presents for sudden worsening
      2. Referred pain is common in children
   2. Night pain may awaken patient from sleep
      1. Distinguishing feature from benign causes
   3. May be misdiagnosed associated with minor injury
      1. Growing Pains (e.g. Osgood Schlatter)
      2. Recent Knee Injury or strain
   4. Uncommon features
      1. Fever
      2. Night Sweats
      3. Weight loss
      4. Lymphadenopathy (think Osteomyelitis if present)
4. Signs
   1. Local tenderness, swelling, mass or deformity
   2. Patient limps
   3. Muscle atrophy
   4. Decreased joint range of motion
   5. Pathologic Fracture
5. Differential diagnosis
   1. Ewing's Sarcoma
   2. Osteomyelitis
   3. Osteoblastoma
   4. Giant Cell Tumor
   5. Aneurysmal bone cyst
   6. Fibrous dysplasia
6. Radiology
   1. Bone XRay
      1. Sclerosis (small, irregular cloud-like densities)
      2. Lytic lesions
      3. Pathologic Fractures
   2. Bone MRI
      1. Defines tumor involvement
         1. Intraosseous and extraosseous changes
         2. Skip lesions
         3. Neurovascular involvement
      2. Used preoperatively
         1. Establishes surgical margins (2-3 cm from tumor)
         2. Establishes resectability
   3. Bone CT with contrast
      1. Preferred over MRI if significant edema and necrosis
      2. Defines neurovascular structures via IV contrast
   4. Other measures used in defining tumor involvement
      1. Bone scintigraphy
      2. Thallium scintigraphy
      3. Angiography
7. Staging (Enneking system)
   1. Stage I: Low-grade tumor
   2. Stage IA: Intracompartmental
   3. Stage IB: Extracompartmental
   4. Stage II: High grade tumor
   5. Stage IIA: Intracompartmental
   6. Stage IIB: Extracompartmental
   7. Stage III: Metastatic disease from either grade
   8. Enneking (1980) Clin Orthop 153:106-20
8. Monitoring
   1. Timing
      1. First 2 years after treatment: Every 3 months
      2. Two to 5 years after treatment: Every 6 months
      3. Five or more years after treatment: Annual
   2. Protocol
      1. Serial Physical exams
         1. Palpate extremity for masses
         2. Assess for prosthetic failure or Infection
      2. Serial XRay of involved limb
      3. Serial CT Chest
         1. Baseline, at time of diagnosis
         2. Repeat every 6 months to 2 years
   3. Additional testing
      1. Bone scan annually for first 2 years
9. Management
   1. Surgery
      1. Limb salvage in most cases (amputation in some)
      2. Tumor resection and limb reconstruction
   2. Chemotherapy
      1. Phases
         1. Induction (pre-operative Chemotherapy)
         2. Adjuvant (post-operative Chemotherapy)
      2. Common Agents used
         1. Cisplatin
         2. Methotrexate (high does)
10. Prognosis
    1. Eligible for limb sparing surgery in U.S.: 90-95%
       1. Contrast with 100% amputation rate before 1970
    2. Long-term survival with localized disease: 60-80%
       1. Contrast with 80% mortality rate before 1970
11. References
    1. Abeloff (2000) Clinical Oncology, Churchill, p. 2170-97
    2. Canale (1998) Campbell's Orthopaedics, Mosby, p. 715-7
    3. Wittig (2002) Am Fam Physician 65(6): 1123-32