A 14-year-old girl from Mumbai presents with a 4-month history of pain and swelling over the proximal tibia. She reports the pain is severe at night and has not improved with paracetamol and ibuprofen. On examination, there is a firm, warm, fixed swelling over the proximal tibia with restricted knee extension. Blood investigations show hemoglobin 11.2 g/dL, alkaline phosphatase 520 IU/L, and normal white cell count. Plain radiographs reveal a mixed lytic and sclerotic lesion in the proximal tibial metaphysis with cortical breakthrough and a 'sunburst' pattern of periosteal new bone. MRI shows a 6 cm × 5 cm lesion confined to the bone with no soft tissue extension. CT chest is normal. What is the most appropriate next step in management?

Explanation

## Management of Osteosarcoma: Multimodal Approach ### Clinical Context **Key Point:** The diagnosis is osteosarcoma based on: - Age (14 years) and location (proximal tibia metaphysis) - Classic radiological findings (sunburst periosteal reaction, mixed lytic/sclerotic lesion, cortical destruction) - Elevated alkaline phosphatase (520 IU/L) - Night pain unresponsive to NSAIDs - Localized lesion without distant metastases (normal chest CT) ### Standard Treatment Algorithm for Osteosarcoma ```mermaid flowchart TD A[Confirmed Osteosarcoma]:::outcome --> B[Staging complete<br/>No distant metastases]:::outcome B --> C[Neoadjuvant Chemotherapy]:::action C -->|3-4 cycles| D[Assess response<br/>Repeat imaging]:::decision D -->|Good response| E[Wide surgical resection<br/>with adequate margins]:::action D -->|Poor response| F[Consider alternative<br/>surgical approach]:::decision E --> G[Adjuvant Chemotherapy<br/>3-4 cycles]:::action G --> H[Surveillance imaging<br/>& clinical follow-up]:::action H --> I[5-year DFS ~70%]:::outcome ``` ### Why Neoadjuvant Chemotherapy? **High-Yield:** Neoadjuvant (pre-operative) chemotherapy is the standard of care because: 1. **Tumor downsizing** — Reduces tumor volume, improving surgical resectability and allowing limb-salvage procedures 2. **Micrometastases control** — Addresses occult systemic disease present in ~80% of patients at diagnosis 3. **Chemosensitivity assessment** — Histological response to chemotherapy is a strong prognostic indicator 4. **Improved survival** — Multimodal therapy (chemotherapy + surgery) achieves ~70% 5-year disease-free survival vs. ~20% with surgery alone ### Chemotherapy Regimen **Mnemonic: CDDM — Cisplatin, Doxorubicin, Doxorubicin, Methotrexate (high-dose)** Standard neoadjuvant regimen: - **Cisplatin** 120 mg/m² IV - **Doxorubicin** 75 mg/m² IV - **High-dose methotrexate** 12 g/m² IV with leucovorin rescue Typically given in 3–4 cycles over 12–16 weeks before surgery. ### Surgical Resection **Clinical Pearl:** Wide surgical resection with adequate margins (2–3 cm) is performed after chemotherapy. In this case, with no soft tissue extension and a 6 cm × 5 cm lesion, limb-salvage surgery (distal femoral or proximal tibial replacement) is feasible. Amputation is reserved for: - Extensive soft tissue involvement - Neurovascular compromise - Pathological fracture with retraction - Recurrent disease after limb-salvage ### Comparison of Management Options | Approach | Outcome | Indication | |---|---|---| | **Neoadjuvant chemo + surgery** | ~70% 5-yr DFS | Standard of care for resectable osteosarcoma | | **Surgery alone** | ~20% 5-yr DFS | Outdated; inferior survival | | **Radiotherapy alone** | Poor response | Osteosarcoma is radioresistant | | **Amputation** | Limb loss | Reserved for unresectable or neurovascular compromise | **Warning:** Immediate surgery without neoadjuvant chemotherapy significantly worsens prognosis by failing to address micrometastatic disease and missing the opportunity to assess chemosensitivity. ### Prognostic Factors **High-Yield:** Good prognostic indicators in this case: - Localized disease (no metastases) - Resectable tumor - Age < 40 years - Tumor size < 8 cm Poor prognostic factors (not present here): - Metastatic disease at presentation - Unresectable tumor - Poor chemotherapy response (< 90% necrosis) ### Follow-up After completion of therapy, surveillance includes: - Clinical examination every 3 months for 2 years, then every 6 months - Chest X-ray every 3 months for 2 years (lung is the most common site of metastasis) - Local imaging (X-ray or MRI) as clinically indicated