MCL-075: Allogeneic Stem Cell Transplantation in Mantle Cell Lymphoma (MCL): Outcomes with Haploidentical Donors at the Sidney Kimmel Cancer Center (SKCC)

Background: MCL is an incurable, aggressive B-cell lymphoma. Allogeneic stem cell transplantation (allo-SCT) is often reserved for relapsed/refractory patients, but upfront allo-SCT transplant in younger patients is feasible and produces durable remissions in high-risk disease. Objective: To describe the SKCC experience with allo-SCT transplantation in MCL. Design: Retrospective data review of all consecutive MCL patients who underwent allo-SCT at SKCC between 1999 and 2019. Results: We identified 16 patients with MCL who underwent allo-SCT. Indications: blastoid variant (N=5), physician preference (n=5), relapse after auto-SCT (N=3), high-risk MIPI (N=2), inadequate autologous stem cell collection (N=1). The majority of patients were male (n=11, 69%) and Caucasian (n=14, 88%) with a median age at transplant of 50 years (range 40-69). Donor source was HLA haploidentical (n=8), matched-related (n=4), and matched-unrelated (n=4). The majority of haploidentical recipients were transplanted on our two-step T-cell tolerization approach. Conditioning was chemotherapy-based myeloablative (n=7) and reduced intensity (n=9); 69% were treated on clinical trial. Pretransplant induction regimens were heterogeneous over this span of time. Disease status at transplant: first complete remission (n=5), second complete remission (n=3), first relapse with chemosensitive disease (n=2), first relapse with chemoresistant disease (n=1), primary induction failure with chemosensitive disease (n=2), not evaluated (n=3). Median follow-up of surviving patients is 104 months (range 11-253). At 5 years, probability of overall survival is 52.5% and in haploidentical vs matched recipients is 73% vs 31%, respectively. Transplant-related mortality was 25% in the total cohort, all of which occurred in patients treated >15 years ago. Graft-vs-host disease (GVHD) occurred in 10/16 (63%) patients, with no GVHD-related death. Conclusions: For patients with aggressive MCL treated at SKCC on or off clinical trial, allo-SCT is feasible and effective, with evidence of a graft-vs-lymphoma effect. The increased tolerability of allo-SCT with recent approaches and the favorable outcomes with haploidentical donor source support the use of allo-SCT in high-risk MCL patients. TP53 gene status in this patient cohort is being evaluated to assess the effect of allo-SCT on outcomes and will be reported.