Pre-Transplant Rituximab Is Associated with Reduced Rate of Acute GvHD After RIC-Allosct In Lymphoma Patients: Results From A Retrospective Monocenter Analysis.
Authors: Crocchiolo Roberto , Cheikh Jean El , Castagna Luca , Helvig Alix , Furst Sabine , Faucher Catherine , Vazquez Alberto , Belmecheri Nawel , Granata Angela , Coso Diane , Bouadaballah Reda , Blaise Didier 
Published: October 2019

Abstract
Abstract 1319

Introduction:
both B and T cells are implicated in the pathophysiology of graft-versus-host disease (GvHD) after allogeneic hematopoietic stem cell transplantation (AlloSCT). Anti-thymocyte globulin (ATG) administered during conditioning has been shown to reduce both acute and chronic GvHD, while rituximab has been claimed to reduce incidence of GvHD: previous studies indicated a reduced incidence of acute and/or chronic GvHD, but sometimes with controversial results. Here we present results from a retrospective, monocenter analysis on a selected population of lymphoma patients undergoing reduced-intensity (RIC) AlloSCT, with or without ATG in the conditioning regimen.

Methods:
adult patients receiving RIC-AlloSCT from a HLA-identical sibling donor for relapsed CD20+ lymphoproliferative disease at our Institution were included in the analysis. Data on patients and donors, conditioning regimen, use of rituximab and cumulative dose during the six and three months before AlloSCT were collected. Rituximab was administered in association or not with chemotherapy, according to each patient's treatment strategy. Analysis was conducted separately on patients receiving ATG (ATG cohort) or not (non-ATG cohort). Correlation analysis between ATG, rituximab cumulative dose before AlloSCT and grade 2–4, grade 3–4 acute GvHD (aGvHD), or limited/extensive chronic GvHD (cGvHD) was performed.

Results:
a total of 57 patients transplanted between Avril 1999 and November 2009 were included in the study, 18 and 39 in the non-ATG and ATG group respectively. Of these 57 patients, 32 were treated with rituximab for a median (range) cumulative dose within 6 months before AlloSCT of 1500 (375-3375) mg/mq, ending at a median (range) of 43 (5-177) days prior to transplant. Details are shown in table 1. Median follow-up was 749 days (146-4051). No significant differences existed between patients receiving rituximab vs. those without rituximab, with the exception of a different number of patients with CLL or FCL. Among the 18 non-ATG patients, we observed a slightly reduced rate of severe (grade 3 or 4) aGvHD in those patients who received >= 375 mg/mq rituximab within three months before AlloSCT (n=13) compared to those receiving < 375 mg/mq or no rituximab (n=5): 2/13 vs. 2/5 (p=ns). In the ATG cohort, rituximab use at a dose >= 375 mg/mq (n=10) within three months was associated with a reduced rate of severe aGvHD compared with < 375 mg/mq or no rituximab (n=29): 0/10 vs. 7/29 (p=0.08). Reduction of grade 2–4 aGvHD rate was also observed: 1/10 vs. 14/29 (p=0.03). No effect on cGvHD appeared in the two cohorts.

Discussion:
present data suggest a role of rituximab administered before AlloSCT in reducing the incidence of aGvHD. This effect was more pronounced when concomitant administration of ATG was performed during conditioning regimen, indicating a possibly sinergistic effect of both T- and B-cell depletion in preventing GvHD. Although retrospective and small-sized, the present analysis, conducted on a quite homogeneous population of patients, confirms previous findings and enhances further investigations on larger number of patients.

Disclosures:
Off Label Use: Zevalin is off-label use in conditioning regimen in France.