Abstract Background High dose chemotherapy followed by autologous stem cell transplantation (ASCT) has become the standard approach for relapsed or high risk non-Hodgkin's lymphoma (NHL). Several different high dose therapy (HDT) conditioning regimens have been used for NHL, such as BEAM(carustine, etoposide, cytosine arabinoside, melphalan), BEAC( carmustine, etoposide, cytosine arabinoside, cyclophosphamide), and CBV(cyclophosphamide, carmustine etoposide). Carmustine is an active drug in the HDT of NHL but the supply of carmustine is limited in some countries. Intravenous busulfan containing regimens as conditioning regimen have been used for both allogeneic and autologous stem cell transplantation in patients with hematologic and non-hematologic malignancies. We and CISL have previously studied that conditioning regimen of i.v. busulfan/melphalan/etoposide was well tolerated and effective in patients with relapsed or high risk NHL. And busulfan/cyclophosphamide/etoposide conditioning regimen has been extensively utilized in ASCT for NHL. Therefore, based on the encouraging results, we conducted a randomized phase II multicenter trial of busulfan/etoposide/cyclophosphamide (BCT) versus busulfan/etoposide/ melphalan/ (BMT) as conditioning therapy for ASCT in patients with NHL. Methods Patients with chemosensitive high risk NHL or relapsed or primary refractory NHL underwent high dose chemotherapy at 16 centers in Korea. Patients were randomly assigned to receive BCT conditioning chemotherapy or BMT conditioning chemotherapy. BCT regimen consisted of iv busulfan 3.2 mg/kg/day i.v. on days -8,-7, and -6, etoposide 400mg/m2 day i.v. on days -5 and -4 and cyclophosphamide 50mg/kg/day i.v. on days -3 and -2 and BMT regimen were iv busulfan 3.2 mg/kg/day i.v. on days -8,-7, and -6, etoposide 400mg/m2 day i.v. on days -5 and -4 and melphalan 50mg/m2/day i.v. on days -3 and -2. The primary efficacy end points were 2 year progression free survival. Results Seventy five patients were enrolled onto the study. Patients randomly assigned to the BCT group (39 patients) or the BMT group (36 patients). Main subgroups were DLBCL (n=42, 56%) and T cell lymphoma (n=27, 36%). Thirteen patients (33.3%) in the BCT group and 11 patients (30.5%) in the BMT group had disease progression or died. 2 year progression free survival rate was 62.5% in the BCT group and 63.1% in the BMT group (p=0.924) (Fig 1). There was no treatment related mortality. Conclusions No significant differences were observed in progression free survival between BCT group and BMT group. Accordingly, busulfan based conditioning regimen may be regarded as an important treatment option to substitute for BEAM regimen. Further, considering R-CHOP or CHOP regimes are standard induction regimens, BMT conditioning will be good alternative to patients who can't be used cyclophosphamide. Figure PFS after autologous stem cell transplantation. Survival rates among all patient who underwent randomiazation Figure. PFS after autologous stem cell transplantation. Survival rates among all patient who underwent randomiazation Disclosures Kim: Celltrion, Inc.: Consultancy, Honoraria.