Neoadjuvant chemotherapy is administered before limb salvage surgery for osteosarcoma. The histological response to chemotherapy is assessed on the resected specimen. A 'good response' (Huvos Grade III/IV) is defined by what percentage of tumor necrosis?
- A >50%
- B >90% ✓
- C >70%
- D >95%
Correct answer: B. >90%
Explanation
The Huvos grading system evaluates histological response to neoadjuvant chemotherapy in osteosarcoma. Huvos Grade III (90–99% necrosis) and Grade IV (100% necrosis) are collectively classified as a 'good histological response' (≥90% necrosis). A good response is associated with significantly improved event-free and overall survival and validates continuation of the same chemotherapy regimen postoperatively. Grades I and II (<90% necrosis) represent poor responses and may prompt chemotherapy modification.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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