A 14-year-old girl from Delhi presents with a 4-month history of progressive pain in the right proximal tibia. She reports the pain is severe at night and wakes her from sleep. On examination, there is a firm, non-tender bony swelling over the proximal tibia. Plain radiographs show a sunburst pattern with a mixed lytic and sclerotic lesion. MRI reveals a large soft tissue mass extending into the anterior compartment of the thigh. Serum alkaline phosphatase is 920 U/L and LDH is 680 U/L. Chest X-ray is normal. What is the most appropriate next step in management?

Explanation

## Management Strategy for Osteosarcoma: Staging Before Treatment ### Diagnostic Confirmation and Staging Algorithm ```mermaid flowchart TD A[Suspected osteosarcoma on imaging]:::outcome --> B{Histological confirmation obtained?}:::decision B -->|No| C[Core needle or open biopsy]:::action C --> D[Confirm diagnosis: osteosarcoma] B -->|Yes| D D --> E{Staging complete?}:::decision E -->|No| F[Chest CT + MRI primary site]:::action E -->|Yes| G[Multidisciplinary tumor board review]:::action F --> G G --> H[Neoadjuvant chemotherapy]:::action H --> I[Surgical resection]:::action I --> J[Adjuvant chemotherapy]:::action J --> K[Follow-up surveillance]:::outcome ``` ### Why Biopsy and Staging First? **High-Yield:** Modern osteosarcoma management follows a **biopsy → staging → neoadjuvant chemotherapy → surgery → adjuvant chemotherapy** protocol. This is the standard of care in all major oncology centers. **Key Point:** - **Biopsy is mandatory** — even with classic imaging, histological confirmation is required before chemotherapy initiation - **Staging is essential** — chest CT excludes pulmonary metastases (present in ~20% at diagnosis); MRI defines soft tissue extent and surgical margins - **Neoadjuvant chemotherapy improves survival** — response to chemotherapy is a strong prognostic factor (>90% necrosis = good prognosis) ### Chemotherapy Regimen **Mnemonic:** **MAP = Methotrexate + Adriamycin (doxorubicin) + Cisplatin** — This is the standard neoadjuvant and adjuvant regimen for osteosarcoma. High-dose methotrexate with leucovorin rescue is a cornerstone. ### Prognostic Factors | Factor | Favorable | Unfavorable | |--------|-----------|-------------| | Tumor size | <8 cm | >8 cm | | Location | Distal femur | Proximal humerus, pelvis | | Chemotherapy response | >90% necrosis | <90% necrosis | | Metastases at diagnosis | Absent | Present | | Age | Younger | Older | **Clinical Pearl:** LDH elevation (as in this case: 680 U/L) correlates with tumor burden and is an independent adverse prognostic factor. ### Surgical Principles - **Wide excision** with adequate margins (≥2 cm soft tissue, full bone compartment) - **Limb-salvage surgery** is preferred over amputation when feasible (>90% of cases) - **Timing:** After neoadjuvant chemotherapy (typically 10–12 weeks) to assess response and allow soft tissue healing ### Survival Outcomes - **With modern multimodal therapy:** 5-year overall survival ~70–75% - **Without chemotherapy:** 5-year survival <20% **Warning:** Immediate surgery without neoadjuvant chemotherapy and staging is suboptimal and reduces long-term survival. [cite:Robbins 10e Ch 26; Harrison 21e Ch 387]