Allogeneic Stem Cell Transplantation for Relapsed/Refractory B-Cell Lymphomas: Results of a Multicenter Phase II Prospective Trial Including Rituximab in the Reduced Intensity Conditioning Regimen.

The treatment of patients with refractory/relapsed B-Cell non-Hodgkin lymphoma (NHL) is evolving due to the availability of novel drugs. Allogeneic stem cell transplantation (alloSCT) can be curative, but its morbidity and mortality remain a matter of concern. We conducted a multicentre prospective phase II trial to evaluate the benefit of including only one dose of Rituximab (R) in the conditioning regimen before alloSCT. The primary end-point was progression-free survival. The study enrolled 121 patients with relapsed/refractory B-cell lymphomas. The conditioning regimen consisted of thiotepa, cyclophosphamide, fludarabine and R (500 mg/ms). Rabbit anti-thymocyte globulin (ATG) was administered only in case of unrelated donors. Sixty-seven (55%) and fifty-four (45%) patients received grafts from related and unrelated donors, respectively. The crude cumulative incidence (CCI) of non-relapse mortality (NRM) was 21% at 3-years. The CCI of chronic GVHD at 3-years was 54% and 31% in recipients of matched sibling and unrelated grafts, respectively. At a median follow-up of 41 months, the estimated 3-years progression-free and overall survival were 50% and 61%, respectively. Long-term outcome was also evaluated with the composite end-point of graft-versus-host disease-free and relapse-free survival (GRFS). This is the first work evaluating the GRFS in a prospective trial of lymphomas patients: the 1 and 3-years GRFS were 40% and 34%, respectively. AlloSCT can cure a fraction of patients with rather low NRM and an encouraging PFS and GRFS.