MFH of Bone and Osteosarcoma Show Similar Survival and Chemosensitivity

BACKGROUND: Patients with malignant fibrous histiocytoma of bone (MFH-B) and osteosarcoma reportedly have comparable survival rates, despite the lesser chemosensitivity of patients with MFH-B compared with those with osteosarcoma. QUESTIONS/PURPOSES: We therefore asked (1) whether there is a difference in the initial tumor volume, histologic response, and survival between cohorts with MFH-B and osteosarcoma, and (2) whether histologic responses and survival rates differed between two groups even after matching for volume and age. PATIENTS AND METHODS: We retrospectively compared 27 patients with Stage IIB MFH-B with 389 patients with localized osteosarcoma for initial tumor volume, age, histologic response, and survival. We compared histologic response and survival between 27 patients with MFH-B and 54 patients with osteosarcoma matched for tumor volume and age. RESULTS: MFH-B occurred more frequently in older patients and they presented with a smaller mean tumor volume and more frequent osteolytic pattern when compared with patients with osteosarcoma. The 5-year metastasis-free survival rates of the MFH-B and osteosarcoma groups were similar: 61.2% ± 9.7% and 61.3% ± 2.5%, respectively. We observed similar proportions of good responders to chemotherapy in the two groups, and the 5-year metastasis-free survival rates were 61.2% ± 9.7% and 70.4% ± 6.2%, respectively. CONCLUSIONS: Patients with MFH-B and osteosarcoma have similar survival rates and histologic responses to chemotherapy. Although MFH-B and osteosarcoma differ in clinical presentation, their response pattern to contemporary therapy is similar. LEVEL OF EVIDENCE: Level III, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.