Low toxicity and efficacy of¹⁵³samarium-EDTMP and melphalan as a conditioning regimen for secondary acute myelogenous leukemia

We report the case of a 15-yr-old girl who developed secondary acute myelogenous leukemia (AML) 4 yr after completion of therapy for metastatic Ewing sarcoma (primary right acetabulum with metastatic disease to the lungs). Peripheral blood stem cells were collected after the second cycle of chemotherapy with the plan for future consolidation with high-dose chemotherapy and autologous stem cell rescue; however, because of the patient's excellent response to chemotherapy and surgery, therapy was completed without the need for high-dose chemotherapy. No human leukocyte antigen (HLA)-matched related donor was available for a bone marrow transplant. Because of previous lung radiation, high-dose samarium [30 mCi/kg of samarium-153 ethylenediaminetetramethylenephosphonate (¹⁵³Sm-EDTMP) day -14] and melphalan (140 mg/m² day -2) were chosen as the conditioning regimen to avoid potential lung complications. The patient received an infusion of 6.1 × 10⁸/kg mononuclear autologous cells on day 0. She achieved engraftment on day +23. Three years after transplantation, she continues to have complete remission. Samarium and melphalan constitute a well-tolerated regimen with potential anti-leukemic activity.