Matched Unrelated Donor Stem Cell Transplantation for Relapsed or Refractory Mantle Cell Lymphoma. A Retrospective Analysis from the EBMT Lymphoma Working Party.

High-dose therapy with allogeneic hematopoietic transplantation (allo-SCT) from matched sibling donors has been shown to induce durable remissions in some patients with relapsed / refractory mantle cell lymphoma (MCL). The aim of this retrospective analysis from the LWP of the EBMT was to investigate the outcome of patients with MCL treated with an unrelated donor allo-SCT (MUD-allo). From January 1994 to July 2005, 66 patients with MCL, 51 males and 15 females, with a median age of 50 years (range, 22 to 68) underwent a MUD-allo and were reported to the EBMT registry. The median time from diagnosis to MUD-allo was 34 months (range, 6–131). Thirty-five patients (53%) had previously failed an autologous procedure (ASCT). Forty-five patients (68%) had sensitive disease (including 22 patients in complete remission) at transplantation, whereas 21 patients (32%) were allografted with refractory disease. Reduced intensity conditioning regimens (RIC) were used in 44 patients (67%). Patients treated with RIC were older, more heavily pre-treated and had more frequently failed an ASCT (46% vs 30%, p = 0.01) than patients treated with a conventional conditioning protocol. Total body irradiation (TBI) was used in 68% of the patients receiving conventional protocols and low-dose TBI in 23% of the RIC patients. Grade II–IV acute graft versus host disease (GVHD) developed in 35% of the cases. The cumulative incidence (CI) of non-relapse mortality (NRM) was of 21% at 6 mo and 27% at 12 mo. The CI of relapse was 35% at 1 year and 45% at 2 years. After a median follow up of 15 months (1–73), 25 patients are alive without progression, with an estimated PFS and OS at 2 years of 28% and 42%, respectively. RIC protocols were not associated with a lower NRM or a better survival. Refractory disease at MUD-allo was an adverse prognostic factor for PFS (RR 1.7; p = 0.006). Patients allografted in sensitive disease presented a better 2-year PFS and OS (34% and 48%, respectively). In conclusion, although follow up is still short, MUD-allo is a feasible procedure in poor prognosis MCL patients, with almost one third of them being alive and progression-free in this series. RIC protocols do not seem to offer any advantage in terms of long-term outcome in relation to conventional conditioning regimens.