Hematopoietic Stem Cell Transplantation (SCT) for Hematologic Malignancy from Matched Related Donors (MRD) with a Myeloablative Once Daily IV Busulfan (Bu)/Fludarabine (Flu) Based Regimen (FLUBUP) with Thymoglobulin: Outcomes in 200 Patients with over One Year Follow-Up.
Authors: Russell James A. , Bahlis Nizar J. , Savoie Mary Lynn , Chaudhry M. Ahsan , Turner A. Robert , Larratt Loree M. , Quinlan Diana M. , Brown Christopher , Balogh Alexander , Storek Jan , Geddes Michelle , Stewart Douglas A. 
Published: October 2019

Earlier reports indicated that a myelablative protocol based on once daily IV Bu with Flu plus rabbit antithymocyte globulin appeared effective and relatively well tolerated. Since 1999 this has been our standard regimen for all pts with hematologic malignancy, including those who might otherwise be candidates for non-myeloablative regimens. Two hundred MRD SCT patients (pts) were treated between 05/99 and 07/05. Chemotherapy comprised fludarabine 50mg/m2 on days -6 to -2 and IV busulfan (Busulfex, PDL Pharma) 3.2 mg/kg daily days -5 to -2 inclusive. Forty-six acute leukemia pts had additional TBI 200cGy x 2 on day (D) -1 or 0. Prophylaxis for GVHD was cyclosporine A, methotrexate with folinic acid and Thymoglobulin (Genzyme) 4.5 mg/kg in divided doses over 3 consecutive days pretransplant finishing D0. Cell source was mobilized blood cells (BCT) in 172 and marrow (BMT) in 28. Median age was 46 (range 18–65) and follow-up of survivors was 13–87 months (median 42). As engraftment and GVHD did not differ significantly data for BMT and BCT were combined. Two pts had graft failure (1 with autologous recovery) and two died before D28. The remaining 196 evaluable pts engrafted granulocytes at median of 16 days (range 2–42). Platelets engrafted in 194 pts at a median of 18 days (0–101), 2 died before engraftment on days 29 & 72. Incidence of acute GVHD grade II-IV, acute GVHD grade III-IV and chronic GVHD was 14±2%, 3±1% and 54±4% respectively. Five pts died before D100 of GVHD (1), candidiasis (1), influenza B (1), veno-occlusive disease (1) and myocardial infarction (1), after D100 15 deaths were related to GVHD (11), pneumonia/ARDS (2), graft failure (1) and pulmonary embolus (1). One case of PTLD resolved with rituxan, there was no serious neurological toxicity. For low-risk (acute leukemia CR1/CR2, CML CP1) pts 3 year TRM was 4±3% for those ≤45 years old (n = 54) and 6±4% for those >45 (n = 31). Corresponding figures for all others (high risk) were 6±4% (n = 40) and 27±7% (18±5% at one year, n = 75) (p = 0.04). [table 1] We conclude that FLUBUP appears to be well-tolerated with little mortality attributable to the regimen itself. In partular, concerns about excessive immune suppression (partularly causing PTLD) and neurotoxicity have not been substantiated. Chronic GVHD is the major cause of non-relapse death. Control of early morbidity and mortality from GVHD may allow intensification of the regimen, for example by adding TBI. There is also evidence that the safety can be improved by monitoring Bu levels. The effect of age on TRM is only apparent in high-risk pts, the challenge is to reduce mortality from chronic GVHD in these individuals without sacrificing graft-vs.-malignancy.

3 year outcomes (%) for groups with >10 pts Disease/stage n survival TRM * p = 0.07 AML CR1/2 (no TBI) 32 66±8 9±5 AML CR1/2 (TBI)* 16 94±6 0 AML advanced (no TBI) 18 22±10 17±9 MDS 15 79±11 24±12 ALL CR1/2 15 73±11 8±7 CML CP1 22 100% 0 CLL/Richter’s (as primary indication) 14 68±13 16±10 Multiple Myeloma 13 54±14 8±7 NHL (low grade/mantle) 21 75±10 17±9 All pts 200 66±3 12±3