## Osteosarcoma Management: Neoadjuvant Approach **Key Point:** The standard of care for localized osteosarcoma is **neoadjuvant (preoperative) chemotherapy followed by wide surgical resection**, which has improved 5-year survival from <20% (surgery alone) to ~70%. ### Rationale for Neoadjuvant Chemotherapy | Benefit | Mechanism | |---------|----------| | **Tumor downsizing** | Reduces soft tissue mass, may allow limb-sparing surgery instead of amputation | | **Early systemic control** | Eliminates micrometastases present in ~80% of patients at diagnosis | | **Histologic response assessment** | Necrosis >90% indicates good prognosis; <90% suggests need for adjuvant intensification | | **Improved survival** | Multimodal therapy: 70% vs. surgery alone: <20% | ### Treatment Algorithm ```mermaid flowchart TD A[Osteosarcoma diagnosed]:::outcome --> B[Staging: CT chest, MRI local]:::action B --> C{Metastatic disease?}:::decision C -->|Yes| D[Systemic chemotherapy ± surgery]:::action C -->|No| E[Neoadjuvant chemotherapy]:::action E --> F[3-4 cycles of MAP]:::action F --> G[Reassess with MRI]:::action G --> H[Wide surgical resection]:::action H --> I[Assess histologic necrosis]:::decision I -->|>90% necrosis| J[Continue same chemotherapy]:::action I -->|<90% necrosis| K[Consider adjuvant intensification]:::action J --> L[Adjuvant chemotherapy]:::action K --> L L --> M[Follow-up: imaging + ALP monitoring]:::action ``` ### Standard Chemotherapy Regimen **Mnemonic: MAP = Methotrexate, Adriamycin (doxorubicin), Cisplatin** - **Methotrexate:** High-dose (8–12 g/m²), followed by leucovorin rescue - **Doxorubicin (Adriamycin):** 75 mg/m² IV - **Cisplatin:** 100–120 mg/m² IV - **Duration:** 3–4 cycles preoperatively (10–12 weeks) - **Toxicity monitoring:** Renal function (cisplatin), cardiac function (doxorubicin), bone marrow suppression ### Surgical Resection **High-Yield:** Wide surgical margins (≥2 cm) are essential to prevent local recurrence. - **Limb-sparing surgery:** Possible in ~90% of patients after neoadjuvant chemotherapy (vs. ~50% without it) - **Amputation:** Reserved for cases with vascular/nerve involvement or inadequate response - **Timing:** 3–4 weeks after completion of neoadjuvant chemotherapy ### Adjuvant Chemotherapy - **Continued MAP:** 2–3 additional cycles postoperatively - **Total duration:** 5–6 months of chemotherapy - **Histologic response:** Guides intensity; poor responders may receive intensified regimens ### Prognostic Factors | Favorable | Unfavorable | |-----------|-------------| | Histologic necrosis >90% | Histologic necrosis <90% | | Distal femur location | Proximal humerus, pelvis | | Small tumor size | Large tumor size | | No metastases | Lung/bone metastases | | Female sex | Male sex | **Clinical Pearl:** Serum alkaline phosphatase is a useful tumor marker for monitoring response and detecting recurrence; normalization after chemotherapy is a favorable prognostic sign. ### Why Not Surgery Alone? - Micrometastases are present in ~80% of patients at diagnosis (not visible on imaging) - Surgery alone results in <20% 5-year survival due to early relapse - Chemotherapy reduces recurrence risk by ~50% ### Why Not Radiation Alone? - Osteosarcoma is **chemotherapy-sensitive** and **radiation-resistant** - Radiation is reserved for palliation or unresectable disease - Radiation increases risk of secondary malignancy [cite:Robbins 10e Ch 26] 
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.