Osteosarcoma

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Osteosarcoma is a type of malignant bone tumour that primarily affects the long bones, such as the femur, tibia, and humerus. It is the most common primary bone cancer in children and adolescents but can also occur in adults.

Aetiology

The exact cause of osteosarcoma is unknown, but several factors contribute to its development:

• Genetic predisposition, including mutations in the RB1 and TP53 genes
• Previous radiation therapy, particularly in childhood, which increases the risk of developing secondary osteosarcoma
• Rapid bone growth, which is why it often occurs during adolescence when bones are growing quickly
• Certain inherited conditions, such as Li-Fraumeni syndrome, Rothmund-Thomson syndrome, and hereditary retinoblastoma

Pathophysiology

The pathophysiology of osteosarcoma involves:

• Malignant transformation of osteoblasts, the cells responsible for bone formation
• Uncontrolled proliferation of these cells leads to the formation of immature bone (osteoid) and tumour growth
• As the tumour grows, it can invade surrounding tissues and spread (metastasise) to other parts of the body, most commonly the lungs
• Osteosarcoma typically develops in the metaphyseal region of long bones, where bone growth is most active

Risk Factors

• Adolescents and young adults, particularly during periods of rapid growth
• Genetic predisposition, including family history of cancer or inherited cancer syndromes
• Previous exposure to ionising radiation
• Paget's disease of bone, which can increase the risk of osteosarcoma in older adults
• Male gender, as osteosarcoma is slightly more common in males

Signs and Symptoms

The signs and symptoms of osteosarcoma include:

• Pain in the affected bone, which may initially be intermittent but becomes more persistent over time
• Swelling or a noticeable lump near the site of the tumour
• Limited range of motion in the adjacent joint
• Pathological fractures, where the bone breaks with minimal trauma due to the underlying tumour
• Systemic symptoms such as fever, weight loss, and fatigue, particularly in advanced cases

Investigations

Specific investigations to diagnose osteosarcoma include:

• Clinical examination: Assessment of pain, swelling, and range of motion in the affected limb.
• Imaging studies:
  • X-rays: Often the first imaging modality used to identify bone lesions characteristic of osteosarcoma.
  • MRI: Provides detailed images of the tumour and its extent in the surrounding soft tissues.
  • CT scan of the chest: To assess for pulmonary metastases, which are common in osteosarcoma.
  • Bone scan or PET scan: To evaluate the spread of the disease to other bones or organs.
• Biopsy: A definitive diagnosis is made through a biopsy of the tumour, which allows for histological examination of the cancer cells.

Management

Primary Care Management

• Initial assessment and referral: If osteosarcoma is suspected, urgent referral to a specialist oncology centre is required for further evaluation and treatment.
• Pain management: Analgesics such as paracetamol or NSAIDs may be used to manage pain while awaiting specialist care.

Specialist Management

• Neoadjuvant chemotherapy: Often administered before surgery to shrink the tumour and reduce the risk of metastasis.
• Surgical resection: The mainstay of treatment, which involves removing the tumour along with a margin of healthy tissue. Limb-sparing surgery is preferred, but amputation may be necessary in some cases.
• Adjuvant chemotherapy: Given after surgery to eliminate any remaining cancer cells and reduce the risk of recurrence.
• Radiotherapy: Generally not used in osteosarcoma due to the tumour's relative radioresistance, but may be considered in certain cases where surgical resection is incomplete.
• Follow-up care: Regular monitoring through imaging and clinical assessment to detect any signs of recurrence or metastasis.

References

1. NHS (2024) Osteosarcoma. Available at: https://www.nhs.uk/conditions/osteosarcoma/ (Accessed: 24 June 2024).
2. National Institute for Health and Care Excellence (2024) Osteosarcoma: Overview. Available at: https://cks.nice.org.uk/topics/osteosarcoma/ (Accessed: 24 June 2024).
3. British Medical Journal (2024) Osteosarcoma: Clinical Features, Diagnosis, and Management. Available at: https://www.bmj.com/content/350/bmj.h2950 (Accessed: 24 June 2024).
4. American Cancer Society (2024) Osteosarcoma. Available at: https://www.cancer.org/cancer/osteosarcoma.html (Accessed: 24 June 2024).

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