Unrelated Cord Blood Transplantation after Reduced Intensity Conditioning (RIC) in Adults with Hematological Malignancy. An EBMT-Eurocord-Netcord, Société Française de Greffe de Moelle et de Thérapie Cellulaire and University of Minnesota Collaborative Study.
Authors: Rocha Vanderson , Rio Bernard , Brunstein Claudio , Renaud Marc , Olivieri Attilio , Sirvent Anne , Tabrizi Reza , Uzunov Madalina , Boudjedir Karim , Ionescu Irina , Rodrigues Celso A. , Gluckman Eliane , Blaise Didier , Wagner John E. 
Published: April 2020

Abstract
Single center studies have demonstrated promising results in recipients of unrelated umbilical cord blood transplantation (UCBT) treated with a reduced intensity conditioning (RIC). However, little is known about risk factors for outcomes with this strategy. We retrospectively evaluated outcomes after RIC-UCBT in 176 patients with hematological malignancies: 116 had acute leukemia (21 ALL, 77 AML, 18 secAML), 36 lymphoid/plasma-cell diseases (6 Hodgkin, 24 NHL, 4 CLL and 2 Myeloma) and 24 myelodysplastic/myeloproliferative diseases (14 MDS and 10 CML). Median follow-up was 12 months (3–80) and median age 45 years (16–76). At transplant, 51% of patients were in advanced phase of disease and 30% had a previous autologous transplants. The conditioning regimen varied according to disease and centre; however, 95% received Fludarabine (FLU)-containing regimen, 55% being FLU-CY-TBI(2Gy), and ATG/ALG was added in 23%. GVHD prophylaxis consisted most commonly (72%) of CsA+MMF. All received a single UCB unit graft that was HLA identical (6/6) (HLA A and B low resolution and DRB1 allelic typing) in 6%, 5/6 in 27%, 4/6 55% and 3/6 in 11%. The median total nucleated cell dose infused was 2.7 × 107/kg. Median time to neutrophil recovery was 20 days (5–56) and probability of neutrophil recovery was 78±3% at day-60. Chimerism analysis at 3 months was complete in 64%, mixed in 16% and absent (autologous reconstitution) in 19%. In multivariate analysis, cell dose (&lt; vs &gt;2.7 × 107/kg, HR=1.6, p=0.02), HLA compatibility (5–6/6 vs 3–4/6, HR=1.5, p=0.04) and use of FLU+CY+TBI versus other regimens (HR=1.7, p=0.01), were independently associated with neutrophil recovery. At day-100, probability of acute GVHD II–IV was 30% (18% grade II; 6% grade III, 6% grade IV), and no risk factor was associated with its incidence. At 1 year, probability of chronic GVHD was 30%. TRM was 38% at 1 year, being 19% for patients given low dose TBI (&lt;6Gy), vs 61% for those without TBI and 40% for those given a low cell dose (&lt;2.7 × 107/kg), vs 21% for the remainder. In multivariate analysis, both factors were associated with TRM. Probability of relapse at 1 year was 41% and it was associated with disease status and aGVHD (26% in those with and 47% in those without aGVHD, p=0.02). DFS at 1 year was 41% for patients with acute leukaemia, 31% for MDS/CML and 42% for lymphoid/plasma diseases. For those treated with FLU-CY-TBI, DFS was 51% as compared to 28% for those treated with other RICs (p=0.0002). In a multivariate analysis, advanced disease status (HR=1.6, p=0.03) and conditioning regimens other than FLU-CY-TBI (HR=1.9, p=0.004) were associated with decreased DFS. In conclusion, cell dose plays a critical role on engraftment and risk of TRM after UCBT in the RIC setting. Specific RIC regimen, namely FLU-CY-TBI, provides better engraftment, reduced TRM and better DFS. These results support the use of FLU-CY-TBI and UCBT as a strategy for broadening the application of transplant to patients previously excluded on the basis of age, co-morbidities and/or absence of a HLA-matched unrelated donor.