Liposome-encapsulated muramyl tripeptide: A new biologic response modifier for the treatment of osteosarcoma

The majority of children who present with osteosarcoma have pulmonary metastases at the time of diagnosis. Despite surgical resection of the primary tumor and aggressive adjuvant chemotherapy, the 2-year metastasis-free survival (MFS) is approximately 66%. The implication of this observation is that these patients harbor "drug-resistant" tumor cells. Therapy failure can be explained by an inherent drug resistance of some metastatic cells in the lung, by an inability to deliver sufficient quantities of drug to the metastatic cells because of side effects, or by the metastatic cells being located in an area where chemotherapy cannot reach them. New forms of therapy are therefore clearly needed if we are to make a further impact in the treatment of osteosarcoma.