Decreased Incidence of GvHD after Reduced Intensity Conditioning and a Fixed T-CELL Dose in Hematological Malingnancy Patients

Introduction: To decrease graft versus host disease (GvHD), the Geneva transplantation team has performed allogeneic hematopoietic stem cell (alloHSCT) with reduced intensity conditioning (RIC) and T cell depletion (TCD) to treat hematological malignancies for older or non fit for myeloablative conditioning patients. This is a new approach of engineering stem cell products that lowers the risk of GvHD while preserving graft versus leukemia (GvL) as much as possible.

Patient and methods: We report a retrospective study of 73 patients who received alloHSCT with RIC and TCD between 2001-2013. The median age was 59 years (21-70), 60% were male. Disease at transplant time was acute leukaemia for 45%, Hodgkin lymphoma and non-Hodgkin lymphoma for 24%, myelodysplastic disorders for 13%, myeloproliferative disorders for 9,3 % and multiple myeloma for 8%. Source of stem cell was peripheral in 96% of the cases. 41% of the donors were matched related donor, 37% matched unrelated donor, 19% mismatched unrelated donor and 3% mistmatched related donor. The conditioning regimen consisted on fludarabine with busulfan or melphalan and ATG. Extensive T-cell depletion was done using Campath in the bag followed by washing procedures to remove free antibody. Fixed number of CD3+ T-cell addback was given on d+1 to preserve GvL with minimal residual disease (MRD) assessment and early donor lymphocyte infusions (DLI) given if MRD positive. Doses of DLI were preserved and frozen at the time of stem cell harvest. GvHD prophylaxis was with ciclosporine and mycophenolate mofetil.

Results: With a median follow up of 5 (0.5-11) years, the 5-year overall survival (OS), disease free survival (DFS), current disease free survival, relapse rate and non relapse mortality (NRM) were 41.7% (95%CI 30.7-53.7%), 38.8% (95%CI 28.8-50.8%), 39,5% (95%CI 27.7-51.7%), 45.3% (95%CI 32.7-57.2%) and 15.8% (95%CI 8.3-25.4%) respectively. The main cause of death was relapse 38.7 % followed by GvHD 17% and infection 1.3%.

In this cohort, the cumulative incidence (CI) of acute GvHD was 15.1% (95% CI: 8.0-24.3%) as well as for acute GvHD grade II-IV. CI of chronic GvHD was 14.7% (95%CI:7.2-23.6%) with extensive chronic GvHD CI being 5.9% (95% CI: 1.9-13.4%).

Five patients received DLI for relapses, 27 for mixed chimerism and 8 for both causes. The average number of DLI was 2. Twenty-eight patients entered CR, 4 PR and 13 did not respond to DLI.

In univariate analysis, two factors GvHD before DLI and GvHD after first DLI have a tendency for favorable impact on OS respectively p=0.093 and 0.071. For DFS, two factors are significant: disease risk index and GvHD after first DLI respectively p=0.013 and 0.044. For NRM disease risk index is the only factor which is statistically significant p=0.005. For relapse no factors were significant.

Discussion: Our study showed a lower rate of acute and chronic GvHD as compared to other studies with unmanipulated stem cells. However, we describe a high rate of relapse incidence and relapse mortality. We have found in univariate analysis two factors statistically significant for DFS GvHD before and after first DLI. Our cohort is a heterogeneous group with different diseases at different stages, which can explain those results. It’s a monocentric study and small number of patient can be a limit for this work. Of note, since 2009 we have changed our strategy introducing a day +100 preemptive DLI infusion in the absence of GvHD, with escalading doses of lymphocytes every 8 weeks up to 5x 10⁷ CD3/kg in the absence of GvHD to improve response. We don’t have enough patients and follow up to draw any conclusion regarding this new strategy. To improve the outcomes, the selection of patients who may receive partial T-cell depletion should be refined, avoiding transplanting patients with high risk of relapse with this strategy. To help decision making, the revised disease risk index as presented by Armand et al. (Blood 2014;123:3664) may be useful.