After 3 cycles of neoadjuvant MAP chemotherapy (methotrexate, adriamycin, cisplatin) for distal femoral osteosarcoma, resection specimen histology shows 98% necrosis. This necrosis response corresponds to Huvos grade and indicates:

• A Huvos grade III (90–99% necrosis) — good response, continue same regimen ✓
• B Huvos grade I (<50% necrosis) — poor response, change chemotherapy
• C Huvos grade IV (100% necrosis) — complete response, no adjuvant therapy needed
• D Huvos grade II (50–90% necrosis) — moderate response, add ifosfamide

Explanation

The Huvos grading system assesses histological response of osteosarcoma to neoadjuvant chemotherapy: Grade I (<50% necrosis), Grade II (50–90%), Grade III (90–99%), Grade IV (100%). Grade III (90–99% necrosis) represents a good histological response and is associated with improved survival; the same adjuvant chemotherapy regimen is continued postoperatively. Only grade IV (complete necrosis) represents perfect response. Grades I and II are poor responses and warrant consideration of chemotherapy modification with agents such as ifosfamide/etoposide, though evidence for benefit of regimen switching remains limited.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.