The Role of In Vivo T-Cell Depletion On Reduced Intensity Conditioning Allogeneic Hematopoietic Cell Transplantation From HLA-Identical Siblings in Patients with Follicular Lymphoma: An European Blood and Marrow Transplantation Study.
Authors: Delgado Julio , Canals Carme , Attal Michel , Thomson Kirsty , Campos Antonio , Martino Rodrigo , Littlewood Timothy James , Jackson Graham H , Milpied Noel-Jean , Maertens Johann , Hunter Ann E. , Janssen Jeroen JWM , Montoto Silvia , Sureda Anna 
Published: October 2019

Abstract
Abstract 3375
Poster Board III-263
Reduced-intensity conditioning (RIC) allogeneic hematopoietic cell transplantation (Allo-HCT) has become a feasible and effective therapeutic approach for younger patients with relapsed or refractory follicular lymphoma (FL). However, there is still much debate regarding the most appropriate conditioning regimen or whether the use of in vivo T-cell depletion (TCD) is beneficial or not for these patients.
We analyzed the outcome of 164 patients with advanced FL reported to the EBMT from 1999 to 2007, who underwent RIC Allo-HCT conditioned with fludarabine plus an alkylating agent. Donors were HLA-matched siblings in all cases. Patients receiving transplants from alternative donors or conditioned with other agents were specifically excluded. The alkylating agent was melfalan in 48% of cases, busulfan in 32% and cyclophosphamide in 20%. Forty-six patients (28%) received anti-thymocyte globulin (ATG), 41 (25%) received alemtuzumab and 77 (47%) did not receive TCD in vivo.
Median age at transplantation was 50 (range 29-64) years, and patients receiving alemtuzumab were significantly younger [45 (33-63)] than those receiving ATG [52 (29-64)] or no TCD [50 (32-64)], P = 0.05. There were no other differences among groups in terms of disease stage or presence of bulky masses at diagnosis, interval from diagnosis to HCT, number of prior therapies, or disease status at HCT.
Engraftment was observed in 161 (98%) patients, with no significant differences among groups. Median follow-up was 43 (1–110) months for survivors. At three years, non-relapse mortality (NRM), relapse rate (RR), progression-free survival (PFS) and overall survival (OS) were 17% (95% CI 12-24%), 23% (17-31%), 60% (52-68%) and 75% (67-82%), respectively, for the entire cohort. The incidence of grade 2-4 acute graft-versus-host disease (GVHD) was significantly higher for patients not receiving any TCD (31%) compared to TCD patients (18%), P = 0.05, and the incidence of chronic GVHD at one year was also significantly higher for the former compared to the latter group (68% vs. 25%, P < 0.001).
There were no significant differences in NRM among groups, but there was a trend towards a higher RR in patients receiving alemtuzumab (40%) or ATG (24%) compared to patients receiving no TCD (16%) (P = 0.15), which translated into a trend towards a significantly shorter 3-year PFS for the alemtuzumab group (42% vs. 69%; P = 0.18). However, there were no differences in the 3-year OS among groups, which was 77% for patients receiving alemtuzumab, 73% for those receiving ATG and 77% for patients not receiving any TCD.
In conclusion, results with RIC Allo-HCT from HLA-identical siblings were very promising for patients with advanced FL. Both alemtuzumab and ATG were effective in reducing acute and chronic GVHD, but had no significant impact on NRM. There was a trend towards a shorter PFS for patients receiving alemtuzumab, which did not translate into a significantly different OS.

Disclosures:
Delgado: Bayer Schering Pharma: Consultancy, Research Funding; Genzyme: Research Funding. Off Label Use: The use of alemtuzumab as a T-cell depleting agent in the context of hematopoietic transplantation is considered off-label.