A 14-year-old girl with biopsy-confirmed osteosarcoma of the proximal tibia (no distant metastases on staging CT and PET-CT) is referred to the orthopedic oncology clinic. Her parents ask about the treatment plan. What is the most appropriate next step in management?

Explanation

## Management of Localized Osteosarcoma **Key Point:** The standard of care for localized osteosarcoma (no distant metastases) is **neoadjuvant (preoperative) chemotherapy followed by wide surgical resection**. This combined approach has transformed osteosarcoma from a uniformly fatal disease to one with 5-year survival rates of 60–70%. ### Why Neoadjuvant Chemotherapy First? 1. **Tumor downstaging:** - Reduces primary tumor volume - Improves surgical margins - Allows better limb-sparing reconstruction 2. **Early treatment of micrometastases:** - ~80% of patients have occult pulmonary micrometastases at diagnosis - Systemic chemotherapy addresses this risk 3. **Prognostic assessment:** - Histologic response to chemotherapy (>90% necrosis) is the strongest predictor of survival - Poor responders may benefit from adjuvant therapy intensification ### Standard Chemotherapy Regimen | Drug | Timing | Notes | |------|--------|-------| | Cisplatin, Doxorubicin, Methotrexate (MAP) | Neoadjuvant (10–12 weeks) | Standard first-line | | Same agents | Adjuvant (post-surgery) | 10–12 weeks | | Ifosfamide | Added if poor response | Salvage option | **High-Yield:** **MAP chemotherapy + wide surgical resection = gold standard**. Neoadjuvant timing is critical: it allows tumor response assessment and maximizes limb salvage rates (>90% of eligible patients). ### Treatment Timeline ```mermaid flowchart TD A[Biopsy-confirmed osteosarcoma]:::outcome --> B[Staging: CT chest, PET-CT]:::action B --> C{Metastases?}:::decision C -->|Yes| D[Palliative/experimental therapy]:::outcome C -->|No| E[Neoadjuvant chemotherapy<br/>10-12 weeks]:::action E --> F[Surgical resection<br/>wide margins]:::action F --> G[Histologic response assessment]:::decision G -->|>90% necrosis| H[Adjuvant MAP chemotherapy]:::action G -->|<90% necrosis| I[Intensified adjuvant therapy<br/>consider ifosfamide]:::action H --> J[Follow-up: CT chest q3mo]:::action I --> J ``` **Clinical Pearl:** Limb-sparing surgery (wide excision with reconstruction using allograft, prosthesis, or rotationplasty) is now preferred over amputation in >90% of cases, provided adequate margins can be achieved and the patient is medically fit. **Mnemonic:** **NWSR** — Neoadjuvant chemotherapy → Wide Surgical Resection. This is the modern standard for localized osteosarcoma. [cite:DeVita, Lawrence, Rosenberg Textbook of Oncology 11e; Enneking and Spanier]