Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

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Osteosarcoma

Basics
Description
  • The most common primary malignant bone tumor in children and young adolescents
  • May occur occasionally in older adults but is much less common than chondrosarcoma and MFH
  • May occur within other lesions (secondary sarcoma) such as Paget disease, bone infarcts, and irradiated bone
  • A highly malignant tumor with invasive local growth and early pulmonary metastasis
    • Bones most commonly affected include those that grow most rapidly :
      • Femur: 41.5%
      • Tibia: 16.5%
      • Humerus: 15%
  • Classification: The many different types of osteosarcoma often are classified by their location and degree of differentiation.
    • High-grade intramedullary: Most common type
    • Well-differentiated intramedullary: Very rare
    • Surface osteosarcomas:
      • Parosteal osteosarcoma: Most common surface osteosarcoma; well differentiated; occurs most commonly on the distal femoral or proximal tibial metaphysis
      • Periosteal osteosarcoma: Intermediate grade, predominantly cartilage with bone formation
      • High-grade: Very rare
    • Osteosarcoma of the jaw: Behaves in a less malignant fashion than high-grade intramedullary osteosarcoma
    • Lesions usually are staged according to the Enneking staging system , most commonly:
      • Stage IIB: High-grade, soft-tissue extension (80-90%)
      • Stage III: Metastatic disease (~10-15%)
  • Synonym: Osteogenic sarcoma
Epidemiology
  • Adolescents in their 2nd decade are the most commonly affected group.
  • The median age range at presentation is 13-17 years .
  • Some authors report a slight male predominance (1.3:1) .
Incidence
  • Primary sarcomas of bone are rare, with only ~2,500 new cases per year in the United States .
  • Osteosarcoma is one of the most common primary bone sarcomas, representing up to 40% .
Risk Factors
  • Osteosarcomas may occur (rarely) in abnormal bone.
    • After irradiation
    • Paget disease
    • Bone infarcts
Etiology
  • The cause of classic high-grade osteosarcoma is unknown.
  • A relationship between incidence and high rates of growth has been noted.
  • Osteosarcoma occasionally develops in areas of pre-existing bone lesions such as Paget disease, fibrous dysplasia, bone infarcts, or OI.
  • The retinoblastoma often is present.
Associated Conditions
Retinoblastoma (high incidence of osteosarcoma)
 
Diagnosis
Signs and Symptoms
  • Pain and swelling are the most consistent symptoms of osteosarcoma.
  • Onset usually is gradual and progressive.
  • Pain is aching and persistent.
  • Many patients report night pain, which awakens them.
Physical Exam
  • A soft-tissue mass often is palpable and tender.
  • The mass frequently is warm and may limit ROM of the adjacent joint.
  • Once diagnosed, patients:
    • Usually undergo a staging workup, including chest CT, MRI of the lesion, and technetium bone scan
    • Should undergo a staging biopsy
Tests
Lab
  • Alkaline phosphatase is elevated in many patients.
  • In patients with a high pretherapeutic alkaline phosphatase level, serial measurements may be used to monitor therapeutic response and tumor recurrence.
  • Serum lactate dehydrogenase also may be elevated.
Imaging
  • The location of osteosarcoma usually is the metaphysis of a long bone.
  • Lesions typically show features of bone destruction, bone formation, periosteal reaction, and a mineralized soft-tissue mass.
  • The classic radiographic appearance is that of a destructive lesion of bone that is itself forming bone.
  • Rapid cortical destruction and periosteal reaction at the proximal or distal margin may produce the classic Codman triangle.
    • Alternatively, radial reactive trabeculation may produce a sunburst appearance.
  • Lesions rarely involve the joint.
Pathological Findings
  • Many subtypes of osteosarcoma have been identified.
    • All osteosarcoma types have a malignant fibrous stroma forming bone as a least common denominator.
    • Broad histologic subtypes are as follows:
      • Fibrogenic
      • Chondrogenic
      • Osteogenic
Differential Diagnosis
  • Infection
  • Ewing sarcoma
  • Giant cell tumor
  • Metastatic disease
  • EOG
Treatment
General Measures
Any patient with a destructive lesion of a long bone that is forming bone should be referred immediately to an experienced musculoskeletal oncologist.
 
Activity
  • Once the diagnosis has been made, activity should be restricted to prevent fracture, which could necessitate an amputation.
  • Patients with lower-extremity tumors are placed on crutches.
Special Therapy
Physical Therapy
  • Most patients with local extremity lesions begin gait training with crutches to prevent pathologic fracture.
  • In the upper extremity, function of the hand and elbow must be maintained.
Medication
  • Multiple chemotherapy regimens are being developed, refined, and evaluated .
  • Current regimens include 3-6 different cytotoxic agents given for 10-12 weeks preoperatively and 6 months postoperatively (see Prognosis section).
Surgery
  • Historically, treatment generally consisted of amputation.
  • Newer surgical techniques and chemotherapeutic regimens allow limb salvage in most cases.
  • Resected bone segments may be replaced by allografts or large-segment metal prostheses, depending on the situation.
  • Limb salvage surgery can be accomplished in up to 90% of patients.
Follow-up
Prognosis
  • Historically, patients with primary osteosarcoma had a 5-year survival rate of only 20-30%.
  • Newer chemotherapeutic regimens are effective in killing occult metastases.
    • With preoperative and postoperative multiagent chemotherapy and wide resection, long-term disease-free survival is 60-70%.
Complications
  • Development of lung and bone metastases is the most feared complication.
    • Metastasis may occur years after diagnosis and treatment, but most occur within the first 2 years.
  • Other complications secondary to limb salvage surgery are relatively common and include:
    • Local recurrence in ~5-10% of patients, usually within 2 years
    • Pulmonary metastases in ~1/3 of patients, usually found within 3 years
    • Infection
    • Pathologic fracture
    • Loosening of prosthetic components
    • Wound breakdown
Patient Monitoring
  • After definitive treatment, patients should be followed to detect recurrence or metastasis.
  • Patients are monitored closely for the first 2 years with CT scans of the chest every 3-4 months to detect pulmonary metastases.
  • Plain radiographs of the limb are performed to detect local recurrences.
Miscellaneous
Codes
ICD9-CM
170.9 Osteogenic sarcoma
 
Patient Teaching
Patients who have been treated successfully must be alert for any new areas of bone pain that could herald a bone metastasis.
 
FAQ
Q: Do all children with osteosarcoma need chemotherapy?
A: Chemotherapy is essential to improve the prognosis from only 20-30% to 65-75% long-term disease-free survival.
 
Q: Does limb salvage increase the risk of systemic spread?
A: Several studies have shown that limb salvage surgery does not increase the risk of pulmonary or bone metastases.
 
Q: Are there poor prognostic findings?
A: Yes, several: Pulmonary metastases at initial presentation, location in the pelvis or spine, increased serum alkaline phosphatase or lactate dehydrogenase, and (very importantly) a poor response to chemotherapy.
 
Q: What are the greatest risks of limb salvage surgery?
A: Local recurrence and deep infection. Both these complications often necessitate amputation.

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