Myeloablative Versus Reduced Intensity Allogeneic Stem Cell Transplantation in Relapsed Hodgkin’s Lymphoma in Recent Years. a Retrospective Analysis of the Lymphoma Working Party of the European Group for Blood and Marrow Transplantation
Authors: Genadieva Stavrik Sonja G , Boumendil Ariane , Thomson Kirsty , Briones Javier , Corradini Paolo , Bacigalupo Andrea , Socie Gerard , Bandini Guiseppe , Finel Herve , Velardi Andrea , Potter Michael , Benedetto Bruno , Castagna Luca , Craddock Charles , Russell Nigel , Dreger Peter , Anna Sureda 
Published: October 2019

Abstract
Introduction. Allogeneic stem cell transplantation (allo-SCT) is a well established therapeutic alternative for those patients with refractory Hodgkin’s lymphoma (HL) who relapse after an autologous stem cell transplantation (ASCT), have chemosensitive disease and a HLA compatible donor available. The impact of the intensity of the conditioning regimen in the outcome of this procedure is still not well understood. An initial retrospective analysis from the European Group for Blood and Marrow Transplantation (EBMT) Lymphoma Working Party (LWP) (Sureda et al, JCO 2010) that compared myeloablative (MAC) with reduced intensity conditioning (RIC) protocols indicated that the high non-relapse mortality (NRM) associated to MAC-SCT translated into a non-significant improvement in progression free survival (PFS) for RIC recipients in spite of the higher relapse rate of the latter. As NRM for MAC-SCT might have decreased over time due to better patient selection, HLA typing and peri-transplant supportive measures, we hypothesize that overall results of more intensive protocols could compare better to RIC-SCT in recent years.
Patients and Methods. We have included in this analysis adult patients with multiply relapsed classical HL treated with an allo-SCT between January 2006 and December 2010 and reported to the EBMT Database. Only first and second allo-SCT was included. Tandem ASCT-allo-SCT was excluded as well as cord blood transplantations and haplo-identical SCT. A total of 313 patients met the inclusion criteria (63 patients treated with a MAC and 250 patients treated with a RIC, definitions following the EBMT criteria). There were 173 males (55%) and 140 females (45%) with a mean age at diagnosis of 29 years and at SCT of 33 years. Mean time from diagnosis to SCT was of 43.3 months. 153 patients (49%) were chemorefractory at the time of allo-SCT and 166 patients (53%) had already failed a prior ASCT. Peripheral blood (PB) was used as the source of stem cells in 88% of the patients. Comparing MAC with RIC groups, the latter one was significantly older at allo-SCT (31 years vs 34 years, p=0.01), had a longer time interval between diagnosis and allo-SCT and preferentially received mobilized PB stem cells (82% vs 91%, p=0.01). There were also more prior autograft failures in the RIC group (56% vs 42%, p=0.006).
Results. With a median follow up for alive patients of 32.5 (9.7 – 52.9) months, overall survival (OS) was 75% and 65%, PFS, 54% and 39%, NRM 11% and 12% and relapse rate after SCT of 37% at 1 year. There were no significant differences in NRM between MAC and RIC patients. Relapse rate was higher in the RIC group, although these differences did not reach statistical significance (55% vs 40% at 24 months, p=0.1). This lower relapse rate translated into an improvement in PFS for the MAC group (48% vs 37% at 24 months, p=0.08) with no differences in terms of OS (71% for MAC vs 61% for RIC at 24 months, p=0.4). Multivariate analysis after adjusting for disease status at the time of SCT showed that the use of RIC protocols was the only independent adverse prognostic factor associated to a higher relapse rate after SCT [HR 0.68, 95%CI (0.38 – 0.98), p=0.04] and to a lower PFS after the procedure [HR 0.65, 95%CI (0.43 – 0.98), p=0.04]. The intensity of the conditioning regimen did not have any impact n NRM in the multivariate analysis. Chemosensitive disease at SCT was the only independent prognostic factor for OS after SCT in the multivariate analysis [HR 1.70, 95%CI (1.17 – 2.46), p=0.005].
Conclusions. This retrospective analysis shows that NRM after MAC protocols is not a significant clinical issue when allografting patients with HL nowadays. On the other hand, using MAC decreases the relapse risk in this highly resistant population of patients, translating into a significant improvement of PFS. MAC protocols should be considered when designing prospective clinical trials in patients with HL candidates for an allogeneic stem cell procedure.

Disclosures
No relevant conflicts of interest to declare.