A 14-year-old girl presents with a 6-week history of pain and swelling over the proximal tibia. She reports the pain is progressive and associated with a palpable mass. Blood investigations show alkaline phosphatase 450 U/L (normal <130) and LDH 520 U/L (normal <240). Plain radiographs reveal a metaphyseal lesion with mixed lytic and sclerotic areas, cortical breakthrough, and a prominent Codman triangle. CT chest is performed as part of staging. What is the most appropriate next step in management after confirming the diagnosis with biopsy?

Explanation

## Management of Osteosarcoma: Neoadjuvant Approach ### Current Standard of Care **Key Point:** Neoadjuvant (preoperative) chemotherapy followed by wide surgical resection is the gold standard for osteosarcoma management and has dramatically improved survival rates. ### Why Neoadjuvant Chemotherapy First? 1. **Tumor downsizing**: Reduces tumor burden and facilitates limb-sparing surgery 2. **Early treatment of micrometastases**: Addresses occult pulmonary disease present in ~80% of patients at diagnosis 3. **Assessment of chemotherapy response**: Histological response (>90% necrosis) is a strong prognostic indicator 4. **Improved limb salvage rates**: Allows wider surgical margins without amputation ### Treatment Protocol ```mermaid flowchart TD A[Osteosarcoma diagnosed]:::outcome --> B[Staging: MRI local + CT chest]:::action B --> C[Neoadjuvant chemotherapy]:::action C -->|3-4 cycles| D[Cisplatin, Doxorubicin, Methotrexate]:::action D --> E[Reassess with MRI]:::decision E -->|Resectable| F[Wide surgical resection]:::action E -->|Unresectable| G[Salvage chemotherapy/radiation]:::urgent F --> H[Adjuvant chemotherapy]:::action H --> I[Surveillance: CT chest q3mo]:::action I --> J[5-year survival ~70%]:::outcome ``` ### Chemotherapy Regimen **High-Yield:** The standard triple-drug regimen is **cisplatin, doxorubicin, and high-dose methotrexate** (MAP protocol). - **Cisplatin**: 100–120 mg/m² IV - **Doxorubicin**: 25 mg/m² IV daily × 3 days - **Methotrexate**: 12 g/m² IV with leucovorin rescue - **Cycles**: 3–4 preoperative cycles, then surgery, then 3–4 postoperative cycles ### Surgical Resection - **Wide resection** with 2–3 cm margin of normal tissue - **Limb-sparing surgery**: Endoprosthetic reconstruction, allograft, or arthrodesis (preferred when feasible) - **Amputation**: Reserved for cases with vascular/nerve involvement or failed limb-sparing attempts - **Timing**: Typically 3–4 weeks after last chemotherapy cycle ### Prognostic Factors | Factor | Good Prognosis | Poor Prognosis | |--------|----------------|----------------| | **Chemotherapy response** | >90% necrosis | <90% necrosis | | **Metastases at diagnosis** | Absent | Present (lungs, bone) | | **Tumor size** | <8 cm | >8 cm | | **Location** | Distal femur, proximal tibia | Pelvis, spine | | **Alkaline phosphatase** | Normal/mildly ↑ | Markedly ↑ | **Clinical Pearl:** Histological response to neoadjuvant chemotherapy (assessed after resection) is the single most important prognostic factor. Patients with >90% tumor necrosis have significantly better survival. **Warning:** Amputation without chemotherapy (option 4) is outdated and results in 5-year survival <20%. Modern multimodal therapy achieves ~70% survival. **Mnemonic: NEOMAP** — **N**eoadjuvant chemotherapy, **E**arly treatment of micrometastases, **O**ptimize limb salvage, **M**AP protocol (cisplatin, doxorubicin, methotrexate), **A**ssess response, **P**ostoperative chemotherapy. [cite:Robbins 10e Ch 26]