Rituximab for Graft-Versus-Host-Disease-Prophylaxis after Allogeneic Stem Cell Transplantation Given as Treatment of High Risk Relapse of Aggressive Lymphoma: Results of a Randomized Phase II Study.

Background: High dose therapy (HDT) followed by autologous stem cell support has poor outcome in patients with primary progressive lymphoma or relapse after primary HDT. Allogeneic SCT may help these patients by exerting an GVL effect. Its use however is hampered by high incidence of severe GVHD and non-relapse mortality in this population. Rituximab has been claimed to reduce the incidene of GVHD without negative impact on the relapse rate.

Patients and Methods: We initiated a randomized phase II study using intermediate conditioning (Fludarabine 125 mg/m², Busulfan 12 mg/kg and cyclophosphamide 120 mg/kg) followed by GVHD prophylaxis with short term mycophenolat mofetil plus tacrolimus. Anti-thymozyte globulin (ATG) was given due to center decision. Patients were randomized to receive two times four doses of rituximab (375 mg/m²) post transplant starting day +21 and day +175 or no additional GVHD prophylaxis. From June 2004 to July 2007 sixty five patients with aggressive NHL were enrolled and 59 were eligible for analysis. Thirty one pts had diffuse large B cell NHL, 3 patients follicular lymphoma grade 3, 7 pts blastic mantle cell lymphoma, 2 pts aggressive marginal zone lymphoma, 2 patients lymphoblastic B cell lymphoma, and 12 T cell lymphoma. 42 (71%) pts received at least one cycle of HDT and autologous SCT prior to alloSCT; 78% had early relapse ( < 12 months) or primary progressive disease, 59% chemo-refractory disease and 48% had progressive disease with high or high intermediate age adjusted IPI immediately prior to conditioning.

Results: Allo-PBPC were obtained from HLA-identical siblings in 17 pts, from matched unrelated donors in 32 pts and from one locus mismatched unrelated donors in 10 pts. 33 patients did receive ATG. Median observation time of surviving patients is 1,8 years. 30 pts died, in 19 patients death was attributed to treatment related causes. After one year, estimated overall survival is 49%, progression free survival is 39%, relapse rate is 28 % and incidence of GVHD > grade 1 is 73%. The last documented lymphoma progress occurred at day 288 after alloSCT. There are no significant differences in OS, PFS and GvHD in relationship to the application of Rituximab.

Conclusion: Intermediate intensity conditioning followed by allogeneic SCT is a valuable treatment option in patients with high-risk relapse of aggressive NHL. The incidence of GVHD and non-relapse mortality is high. On the background of this very high basic incidence of GVHD, we did not find a significant impact of post transplant rituximab on GVHD, relapse rates or survival, respectively. Therefore, ATG will be added as an obligatory part of the conditioning regimen in the next study phase in additional 30 patients