Effectiveness of mifamurtide in addition to standard chemotherapy for high-grade osteosarcoma: a systematic review

Osteosarcoma mostly occurs during the period of rapid bone growth in children and adolescents as high-grade osteosarcomas. Current treatment recommended for high-grade non-metastatic and metastatic and/or relapsed osteosarcoma involves neoadjuvant multiagent conventional chemotherapy, followed by surgical resection of macroscopically detected tumor and postoperative adjuvant chemotherapy. However, residual micrometastatic deposits that develop following surgery have shown resistance to postoperative/adjuvant chemotherapy. Therefore, there is a critical need for more effective and innovative therapeutic approaches such as immune stimulatory agents. The most extensively studied immune stimulatory agent in the treatment of osteosarcoma is mifamurtide. The aim of this systematic review was to identify and synthesize the evidence on the effectiveness of mifamurtide in addition to standard chemotherapy on survival outcomes.

To present the best available evidence on the treatment of high-grade non-metastatic and metastatic osteosarcoma with mifamurtide in addition to standard chemotherapy.

All populations of patients regardless of age, gender or ethnicity with high-grade, resectable, non-metastatic and metastatic osteosarcoma based on histological diagnosis.

This review focused on intravenous infusion of either of the pharmaceutical formulations of mifamurtide (MTP-PE or L-MTP-PE) in addition to standard chemotherapy, and the comparator was chemotherapy alone.

This review considered any experimental study design including randomized controlled trials, non-randomized trials and quasi-experimental studies.

The primary outcomes of interest were event-free survival, overall survival and recurrence of osteosarcoma. Secondary outcomes that were considered included health-related quality of life and any mifamurtide-related adverse events.

A search for published and unpublished literature in English was undertaken (seven published literature databases, four unpublished literature databases, and three government agency and organizational websites were searched). Studies published between 1990 to June 2016 were considered. A three-step strategy was developed using MeSH terminology and keywords to ensure that all relevant studies were included related to this review.

The methodological quality of included studies was assessed by two reviewers, who appraised each study independently, using a standardized Joanna Briggs Institute (JBI) critical appraisal tool.

Data was extracted from the studies that were identified as meeting the criteria for methodological quality using the standard JBI data extraction tool.

Due to the heterogeneity of populations and interventions in available studies, meta-analysis was not possible and results are presented in narrative form.

Three papers outlining two studies involving 802 patients evaluated the effectiveness of mifamurtide in addition of chemotherapy. Results indicated no significant difference in event-free survival between the addition of mifamurtide to standard chemotherapy regimen and chemotherapy alone, both in non-metastatic and metastatic osteosarcoma patients. There was a significant difference in progression-free survival favoring the addition of mifamurtide in pulmonary metastatic and/or relapsed osteosarcoma. There was no significant difference in overall survival between the addition of mifamurtide and chemotherapy alone in metastatic osteosarcoma; however there was a significant difference favoring the addition of mifamurtide in non-metastatic osteosarcoma patients. The addition of mifamurtide resulted in a significant difference in survival after relapse in pulmonary metastatic and/or relapsed osteosarcoma patients. Both studies reported on mifamurtide-related adverse events - the first was reported as toxicity which included haematological, hepatic, renal, gastrointestinal disorders, cardiac, rhythm and nervous system disorders, ear disorders and others (infection, fever; and performance status) in metastatic osteosarcoma patients. Results were similar across all combined treatment regimens. Although no statistical analysis was undertaken, the figures suggest there were no significant differences between the treatment regimens. In the other study, mifamurtide-related adverse events were reported as clinical toxic effects of mifamurtide in relapsed osteosarcoma, which included chills, fever and headache for the initial dose of mifamurtide, while for the subsequent doses of mifamurtide all patients reported toxicity as delayed fatigue.

The available evidence on the effectiveness of mifamurtide in addition to a standard chemotherapy regimen for the treatment of high-grade osteosarcoma is limited and therefore no definitive conclusions can be made.