Introduction

Osteosarcoma is the most common malignant primary bone tumour, although they are still very rare. It frequently occurs in late childhood and tends to arise in the metaphyses of the long bones. It may present with pain, swelling or a pathological fracture. Treatment involves resection and chemotherapy. The cure rate is approximately 50% as metastatic disease is not uncommon.
Osteosarcomas often occurs in adults, although in these circumstances they are more likely to be secondary lesions (e.g. to Paget’s Disease of the Bone)

Epidemiology & Aetiology

  • Rare – incidence of about 1 per 350,000 annually
  • The most common bone malignancy in adolescents and young adults
  • One of the most common malignancies in adolescents and young adults
  • Peak incidence age 13-16 – associated with the adolescent growth spurt
    • Present earlier in girls – associated with their earlier age of onset of growth spurt
  • M>F
  • Usually occurs at the metaphysics (growth plate) of the long bones (e.g. femur, tibia, humerus)
    • 75% of cases are in the distal femur
    • These areas have the highest rate of bone growth during adolescence
  • In adults, osteosarcoma is more likely to occur in the axial skeleton
  • Later age of onset is associated with higher likelihood of metastasis
  • Risk factors:
    • Prior radiation or chemotherapy
    • Pre-Existing Paget’s disease or other being bone lesions – e.g. osteochondroma¬†– probably due to increased rate of bone turnover in these other conditions
    • Family history
    • Congenital genetic disorders
  • Long-term survival in all cases is about 50%, however, long-term survival in the presence of overt metastasis at presentation is only about 20%

Presentation

  • Bone pain, usually localised to a specific spot, typically of several months duration by the time of presentation
    • May start after an injury
    • Pain can be intermittent and vary in severity over time
    • There is often a palpable soft tissue mass overlying the bone at the site of the pain
  • Blood tests
    • May show elevated alkaline phosphatase, ESR and LDH
      • Lactate dehydrogenase (LDH) levels are correlate to prognosis – higher levels indicate a poorer prognosis
      • ESR is not correlated to severity of the disease
  • 10-20% of patients have metastasis at the time of presentation. Common sites of metastasis include:
    • Lungs
    • Bone
  • Often metastasis are microscopic and not clinically evident – as a result – ALL patients are treated with chemotherapy
    • Patients with obvious clinical metastatic mass at presentation have a worse clinical outcome

Diagnosis

  • X-ray
    • Indistinct margins of bony lesion
    • Local invasion into soft tissues
    • Destruction of normal trabecular bone pattern
  • Biopsy is required for definitive diagnosis, and should be performed by an orthopaedic surgeon
  • Staging usually requires
    • MRI of the entire length of the long bone
    • CT thorax to assess for any metastases
      • May miss up to 1/3 of lung mets
    • Radionuclide bone scan – with technetium (or PET scan) – can be useful to identify any other areas of high bone turnover which may represent metastasis

Management

  • Surgical excision of the primary lesion
    • Local excision is as effective as amputation for most patients and as such, amputation is rare
  • Chemotherapy is usually given to all patients – regardless of any identified metastasis – as the level of occult metastasis is high
    • Typically pre-surgical chemotherapy
  • Radiotherapy is not usually used as osteosarcoma is resistant to radiotherapy
  • Patients with only lung metastases have a better prognosis than those with metastasis of other locations

References

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