The Addition of Mifamurtide To Adjuvant Chemotherapy For Early Osteosarcoma: A Retrospective Analysis From Greece.

Background: Current treatment recommendations for high grade non-metastatic osteosarcoma include perioperative chemotherapy and surgery. Despite this intensive protocol, approximately 40% of patients will relapse. The addition of mifamurtide to adjuvant cytotoxic chemotherapy was associated with a significant improvement in 6-year overall survival (OS) in young patients with resectable osteosarcoma, leading to its approval in Europe and other countries. Very limited real-world data are reported on its use.Methods: We retrospectively evaluated data from osteosarcoma patients who received mifamurtide in the adjuvant setting. Data were obtained from medical records in 2 high-volume bone sarcoma centers. The aim of this study was to collect real-world data on mifamurtide safety and efficacy in Greece. Results: We identified 15 patients with completely resected osteosarcoma who received mifamurtide from September 2015 to January 2020. Median age at diagnosis was 24 years old (16-76). Osteosarcoma arose in the lower extremities (n=12), in the upper extremities (n=2) or in the ilium (n=1). The majority of patients (n=13) received cisplatin/doxorubicin/methotrexate as perioperative chemotherapy and the remaining patients cisplatin/doxorubicin. After a median follow-up of 46.9 months (range, 32.8-61.1), the median recurrence-free survival was 58.7 months (range, 18.5-98.8) and the median OS 64.1 months (range, 25.6-102.6). Except for fever and chills, the only adverse event probably related to mifamurtide was pericarditis (n=1). Conclusions: Mifamurtide was well tolerated in a Greek osteosarcoma population, including patients older than 30 years. The small sample size and the non-comparative design do not allow drawing conclusions on the drug benefit in terms of survival.