Ege Tıp Dergisi

Öz

Introduction: Ewing sarcoma is responsible from 6–9% of the primary malignant bone tumors. Before the modern chemotherapy era, survival time of these patients were the same as other tumor cases. Nowadays, by using multiple chemotherapy regimens, survival time is much longer than before. However, some patients respond to chemotherapy very well while some others don’t. This may be related to multiple drug resistance (MDR) of the tumor cells. Located on the cytoplasmic membrane, P-glicoprotein (PGP) regulates the excretion mechanisms of the drugs outside the cell. Treatment protocol of Ewing sarcoma usually consists Vincristin, Actinomycin-D, Cyclophosphamide and Adriamicin. Except Cyclophosphamide, all the other drugs are the substrates of PGP. So, in tumors in which we can show the PGP positivity, we can assume that they are resistant to the so-called drugs. Materials and methods: In our study conducted between the years 1986–1999, 36 cases of Ewing sarcoma treated with POG#8850 (VAC+Adr) chemotherapy protocol were included in “Ewing sarcoma PGP prognostic group”. C494 monoclonal antibody which recognizes the external epitope of PGP was administered to all patients. Results: PGP was found focally positive in 5 and diffusely positive in 15 of the cases. Sixteen cases were negative for PGP. There was significant difference in survival times between diffusely positive PGP cases and the negative ones. There was no significant difference between focally positive PGP group and the others. Discussion: The results of this study indicate that PGP positivity in tumor cells can limit the efficacy of chemotherapy in Ewing sarcoma cases. We think that demonstration of PGP values in the first biopsy may help us in choosing the most appropriate chemotherapeutic agents.