Bfr (bendamustine, fludarabine, rituximab) Nonmyeloablative Allogeneic Conditioning Improves Survival in Relapsed/Refractory Chronic Lymphocytic Leukemia (CLL).
Authors: Khouri Issa F. , Saliba Rima M , Ledesma Celina , Jabbour Elias J. , Turturro Francesco , Alatrash Gheath , Ahmed Sairah , Oran Betul , Patel Krina K , Olson Amanda , Marin David , Popat Uday R. , Suki Tina S , Jorgensen Jeffrey L. , Medeiros L. Jeffrey , Gulbis Alison M 
Published: October 2019

Abstract
Background: Bendamustine is a novel active agent in CLL with favorable safety profile. We recently reported the preliminary results of allogeneic stem cell transplantation (alloSCT) in lymphoma/CLL patients (pts) after BFR conditioning (Khouri et al. Blood 2014; 124:2306). Herein, we report more mature outcomes in CLL pts. Results and safety were compared with a previous regimen using FCR (fludarabine, cyclophosphamide, rituximab).
Patients and Methods: We studied 89 CLL pts treated on 3 trials (one includes FCR later changed to BFR) at our center. Twenty-six (29%) pts received BFR and 63 (71%) received FCR. The BFR regimen consisted of bendamustine 130 mg/m2 IV daily on days -5 to - 3 prior to transplantation, thus substituting the cyclophosphamide in the FCR regimen. The dose and schedule of fludarabine (30 mg/m2 IV daily on days -5 to -3) and rituximab (375 mg/m2 IV on day -13 and 1000 mg/m2 on days -6, +1, +8) were similar in both regimens. Tacrolimus and mini-methotrexate were used for GVHD prophylaxis. In addition, thymoglobulin 1 mg/kg IV was given on days -2, and -1 in patients receiving a matched unrelated donor (MUD) transplant.
Results: Patient characteristics were similar in both groups. This included median age (58 years in both), sex distribution, and median number of prior therapies (3 in both), % pts with β2-microglobulin >3 mg/L at study entry, refractory disease (38% in BFR vs. 48% in FCR, P=0.4), presence of 17p deletion [27% in BFR vs. (8/33) 24% in FCR], unmutated status [19/21 (90%) of BFR vs 22/24 (92%) in FCR] and peripheral blood stem cell source (92% in BFR vs. 87% in FCR). Donor/recipient CMV and sex-mismatched distributions were not significantly different between the groups. However, more patients received their transplants from unrelated donors in the BFR group than the FCR group (54% vs. 32%, P=0.05). Ten (38%) BFR pts vs 2 (3%) FCR pts did not experience severe neutropenia (P <0.001) and 21 (81%) vs 39 (63%), respectively, did not require platelet transfusions (P=0.08). Median follow-up times for BFR and FCR groups were 29 (range 19-60), and 104 (range, 34-195) months. The 3-year overall survival (OS) estimates in the BFR and FCR groups were 82% vs. 51% (P=0.03) and the 3-year progression-free survival estimates were 63% vs. 27% (P=0.001). The 3-year OS improvements were seen across the prognostic factors studied for BFR and FCR respectively: MUD (93% vs 30%), presence of 17p deletion (86% vs 50%), and age >50 years (79% vs 50%), β2-microglobulin >3 mg/L (73% vs 45%), >3 prior lines of therapy (70% vs 43%) and recent years of transplant (82% vs 47%). Treatment-related mortality was 11% and 27% (P=0.05) at 2-year. The incidence of acute grade 3 GVHD was 4% and 10% in the BFR and FCR groups, respectively, despite the higher % of MUD transplants in BFR. Grade 4 acute GVHD was not observed in either group. The 3-year incidence of extensive chronic GVHD in BFR vs FCR was 45% vs 58% (P=0.01). This difference in GVHD incidence may in part be explained by a lower absolute blood level of CD8+ T cells in BFR patients compared to the FCR group at 6 months (median 343 vs 538, respectively) and 9 months (median 208 vs 406, respectively) post alloSCT.
Conclusions: This is the first study to show that conditioning in alloSCT for CLL impacts outcomes with an improved survival after BFR when compared to the FCR regimen.

Disclosures
No relevant conflicts of interest to declare.