ETOPOSIDE IN COMBINATION WITH CYCLOPHOSPHAMIDE AND TOTAL-BODY IRRADIATION OR BUSULFAN AS CONDITIONING FOR MARROW TRANSPLANTATION IN ADULTS AND CHILDREN

Purpose: In an attempt to intensify conditioning therapy for bone marrow transplantation of hematologic malignancies, a retrospective three center evaluation of escalating doses of etoposide added to cyclophosphamide and either total body irradiation or busulfan was undertaken. Methods and Materials: Seventy-six patients who received etoposide (25-65 mg/kg) added to cyclophosphamide (60-120 mg/kg) and either total body irradiation (12.0-13.2 Gy) or busulfan (12-16 mg/kg) were evaluable for toxicity. Fifty-one of the evaluable patients received allogeneic transplants, while twenty-six received autologous transplants. A comparative analysis of toxicities according to conditioning regimen, donor source and etoposide dose was made. Results: Similar toxicities were observed among the treatment groups with the exception of more frequent skin (p = 0.003) and life threatening hepatic toxicities (p = 0.01) in the busulfan treated patients. Life threatening or fatal toxicities were not influenced by donor source, either when analyzed by treatment group or etoposide dose. Etoposide at a dose of 60-65 mg/kg in combination with TBI and cyclophosphamide was associated with a significantly increased incidence of life threatening or fatal toxicities compared with a combination using a dose of 25-50 mg/kg (15 of 24 vs. 5 of 20; p = 0.013). The maximally tolerated dose of etoposide in combination with busulfan and cyclophosphamide cannot be definitively established in this analysis in part due to the heterogeneity of the patient population and treatment schemes. Conclusion: Although toxicities with bone marrow transplant preparative regimens containing etoposide in combination with cyclophosphamide and total body irradiation or busulfan were frequently severe, treatment related mortality risk was believed to be acceptably low.