Biphenotypic acute leukemia is a rare disease accounting for approximately 10% of acute leukemias using the new scoring system. No standard therapeutic approach exists for this entity. In addition, the prognosis for these patients (pts) is poor and thought to be worse than for acute myelogenous leukemia (AML). ASCT may provide improved disease free survival for patients with high risk AML, but its role in BAL is unknown. We undertook a retrospective study of pts with BAL to determine if outcome was similar following ASCT to pts with AML in first remission. Between 7/93 and 2/04, nine patients with BAL who underwent ASCT were identified. Criteria for the diagnosis of BAL was based on the scoring system adapted from the European Group of Immunological Classification of Leukemia. Pts with Philadelphia positive acute lymphoblastic leukemia (ALL) were excluded. Cytogenetics at presentation included 1 pt with deletion7 and trisomy 8, 1 with 11q23, 2 with complex karytoype, 4 with normal cytogenetics ,1 unknown. Six pts were treated with an AML induction of Idarubicin/Cytarabine, two with an ALL regimen Daunorubicin/Vincristine/Prednisone and one with an Idarubicin- AML based first induction, and then a combination of an ALL/AML reinduction at first relapse. Eight pts were in first complete remission (CR) and one pt in second CR at ASCT. Median age at ASCT was 34 years (range 11–60). Median time from diagnosis to ASCT was 3.4 mos (range 1.5–5.2). Seven pts received sibling donor (SIB) and two received unrelated donor (URD) stem cells. Two pts received marrow and seven received peripheral stem cells. The conditioning regimen consisted of 1320cGy total body irradiation (TBI)+VP16 60mg/kg in 6 pts, 1320cGy TBI+Cyclophosphamide 120mg/kg in 1 pt, Fludarabine125mg/m2+Melphalan 140mg/m2 in 2 pts. Seven received a Cyclosporin- based graft versus host disease prophylaxis regimen (GVHD) and two a Tacrolimus- based regimen. Six pts developed grade III GVHD. Two patients died of pulmonary toxicity, one of GVHD, one from infection and one from disease relapse. One year overall survival (OS) is 39%( 95% CI 13–73). The relapse rate at one year was 20%. In conclusion, despite unfavorable cytogenetics in many patients, relapse rates are low following ASCT for BAL and comparable to pts undergoing ASCT for AML. Future approaches include methods to reduce transplant related mortality which was the major cause of reduced survival in this series.

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