Post-transplant Donor Lymphocyte Infusions Research Articles

Persistence of KIRneg NK cells after haploidentical hematopoietic stem cell transplantation protects from human cytomegalovirus infection/reactivation.

Haploidentical hematopoietic stem cell transplantation (h-HSCT) is a therapeutic option to cure patients affected by hematologic malignancies. The kinetics and the quality of immune-reconstitution (IR) impact the clinical outcome of h-HSCT and limit the onset of life-threatening Human Cytomegalovirus (HCMV) infection/reactivation. Natural Killer (NK) cells are the first lymphocytes that recover after h-HSCT and they can provide rapid innate immune responses against opportunistic pathogens. By performing a longitudinal single-cell analysis of multiparametric flow-cytometry data, we show here that the persistence at high frequencies of CD158b1b2jneg/NKG2Apos/NKG2Cneg/NKp30pos/NKp46pos (KIRneg) NK cells is associated with HCMV infection/reactivation control. These KIRneg NK cells are "unlicensed", and are not terminal-differentiated lymphocytes appearing early during IR and mainly belonging to CD56bright/CD16neg and CD56bright/CD16pos subsets. KIRneg NK cells are enriched in oxidative and glucose metabolism pathways, produce interferon-γ, and are endowed with potent antiviral activity against HCMV ex vivo. Decreased frequencies of KIRneg NK cells early during IR are associated with clinically relevant HCMV replication. Taken together, our findings indicate that the prolonged persistence of KIRneg NK cells after h-HSCT could serve as a biomarker to better predict HCMV infection/reactivation. This phenomenon also paves the way to optimize anti-viral immune responses by enriching post-transplant donor lymphocyte infusions with KIRneg NK cells.

Post-Transplant MRD Negativity on Day +100 Predicts Outcomes for Pre-Transplant Relapsed/Refractory AML Patients

IntroductionPatients with relapsed/refractory (r/r) AML have in general a dismal prognosis. Allogeneic stem cell transplantation (allo-SCT) provides a curative approach for these patients, however the overall survival (OS) remains still low achieving 20-40%. Though post-transplant minimal residual disease (MRD) monitoring has been shown to be predictive for development of post-transplant relapses and lower survival, data focusing on pre-transplant relapsed/refractory AML patients is scarce. In this study, we investigated the impact of achieving MRD negativity on day +100 for relapses and survival for this high risk patients.Patients and MethodsWe analyzed post-transplant outcomes for pre-transplant r/r AML patients depending on their post-transplant MRD status at day +100. The day +100 was chosen concerning the possibility of early post-transplant interventions (e.g. tapering of immunosuppression or administration of donor lymphocytes).Fifty six consecutive adult patients (≥18 years old) with r/r AML (median age 58, range 20-76; male, n=34, 61%) who underwent allo-SCT (first, n=44, 79%; second, n=12, 21%) between 2015-2020 at the Department for Stem Cell Transplantation at the University Medical Center Hamburg (Germany) were included. The MRD was assessed on day +100 using multiparameter flow cytometry according to “different from normal” strategy.The patients experienced rather primary refractory disease (64%), secondary/therapy-related AML (55%) and abnormal cytogenetics (59%) at diagnosis. The median pre-transplant blast count was 25% (6-91%). A number of 29 patients (52%) showed blasts in peripheral blood. Myeloablative conditioning was used in 31 (55%) patients, whereas 25 (45%) patients received reduced intensity regimens. A number of 29 patients (52%) received a FLAMSA-based conditioning. Post-transplant donor lymphocyte infusions as well as other treatment were given to 13 (23%) and 17 (30%) patients, respectively.ResultsThe median follow up was 20 months (range 4-66). Forty patients (71%) achieved MRD negativity on day +100 and 16 (29%) remained MRD positive. The 2-year OS, LFS, relapses and NRM at 2 years for day +100 MRD negative patients were: 76% (95% CI: 60-87%), 59% (95% CI: 41-75%), 31% (95% CI: 17-50%) and 8% (95% CI: 3-19%), respectively. The 2-year OS, LFS, relapses and NRM at 2 years for day +100 MRD positive patients were: 35% (95% CI: 17-59%, p=p=0.001), 23% (95% CI: 9-46%, p<0.0001), 70% (95% CI: 45-87%, p=0.0002) and 6% (95% CI: 1-28%, p=0.88), respectively.Several factors were evaluated for possible association with day +100 MRD negativity (Table 1). There were no significant associations. Further, the incidence of acute (grade II-IV) GvHD at 100 days was not significantly different between the day 100 MRD positive und negative patients.Following factors had impact on post-transplant outcomes in multivariate analysis: presence (no vs yes) of peripheral blasts prior to allograft (OS: HR 0.3, 95% CI: 0.1-0.9, p=0.03; LFS: HR 0.4, 95% CI: 0.1-0.9, p=0.03; relapses: HR 0.4, 95% CI: 0.1-0.99, p=0.048; NRM: HR 0.5, 95% CI: 0.2-1.3, p=0.17), FLAMSA vs other preparative regimens (OS: HR 0.4, 95% CI: 0.1-0.93, p=0.03; LFS: HR 0.4, 95% CI: 0.2-0.98, p=0.04; relapses: HR 0.4, 95% CI: 0.2-1.0, p=0.05; NRM: HR 0.4, 95% CI: 0.2-1.0, p=0.06), and day +100 MRD (negative vs positive) (OS: HR 0.3, 95% CI: 0.1-0.7, p=0.009; LFS: HR 0.2, 95% CI: 0.1-0.6, p=0.001; relapses: HR 0.2, 95% CI: 0.1-0.4, p=0.0001; NRM: HR 0.2, 95% CI: 0.1-0.5, p=0.0006).ConclusionsPost-transplant MRD detection plays predictive role in pre-transplant r/r AML patients and may help to define possible candidates for early post-transplant interventions. DisclosuresNo relevant conflicts of interest to declare.

Post-Transplant Donor Lymphocyte Infusion with Methotrexate Prophylaxis Is Associated with Low Incidence of Relapse after CD34-Selected, T Cell-Depleted Haploidentical Donor Stem Cell Transplantation Regardless of NK Alloreactivity

▪Background: NK alloreactivity based on KIR (Killer Immunoglobulin-like Receptor) expression by natural killer cells has been reported to decrease the risk of leukemia relapse after HLA-haploidentical stem cell transplantation (SCT). The use of donors with high KIR B-content score has been correlated with a decreased risk of relapse.Objective: We examined the outcome of leukemia relapse following CD34-positive selected T-cell depleted haploidentical donor peripheral blood SCT followed by donor lymphocyte infusion with methotrexate prophylaxis.Methods: Between 2009-2015, twenty patients underwent haploidentical donor CD34-selected, T cell-depleted peripheral blood SCT on an IRB-approved protocol. Nine patients had acute lymphoblastic leukemia (ALL), and eleven had myeloid leukemia (10 AML, 1 JMML). Among ALL patients, remission status was CR1 in 5, with either induction failure or MRD+ after consolidation, 3 were in CR2 and 1 was CR3. Four patients had T-cell disease. Among AML patients, 5 were in CR1, one had refractory disease and 5 were CR2 or beyond. Ligand-ligand NK alloreactivity based on HLA typing was available for all patients. Receptor-ligand NK alloreactivity based on immunophenotyping of KIR was available in 16 patients and KIR B-content score was available in twelve patients. Patients were considered to have receptor-ligand NK alloreactivity if immunophenotyping of the donor had >5 (cells/uL) expressing KIR2DL1 (recognizes C2 group) or KIR2DL1/2DL13 (recognizes C1 group). Patients with alloreactive KIR only recognizing BW4 were not considered alloreactive due to predicted weak alloreactivity. All patients received a uniform conditioning regimen including TBI 1200cGy, thiotepa 10mg/kg, fludarabine 200mg/m2, and rabbit-anti-thymocyte globulin (rATG) 6mg/kg, with no post-transplant immunosuppression. All patients received a planned donor lymphocyte infusion (DLI) 3-5 x 104 CD3+ cells/kg between days 30- 42 after transplant and received weekly IV methotrexate prophylaxis following DLI. The incidence of relapse and GVHD was evaluated.Results: Based on a ligand-ligand model of NK alloreactivity, only 4/20 patients had NK alloreactivity predicted. Seven patients expressed all 3 ligands and blocked all possible NK alloreactivity. Median follow-up was 306 days (range 45 days-5 years). Four of 20 patients relapsed (1/4 with predicted NK alloreactivity and 3/16 without). Median time to relapse was 110 days (range 124-455 days). NK alloreactivity based on receptor-ligand as defined above was present in 5/16 patients and relapse occurred in 2/5 with and 1/11 without. Donor KIR B-content was >=2 in 4 patients and 0-1 in 8 patients. Relapse occurred in 1/4 with 2 and 2/8 with 0-1. No donors had KIR B-content score of 3-4. The incidence of grade II-IV acute graft-versus-host disease after prophylactic DLI was 25%, with 2 grade II, 3 grade III and no grade IV GVHD. Three patients developed cGVHD, two mild and one severe by NIH consensus criteria.Conclusion: An approach using a DLI followed by methotrexate prophylaxis after a CD34-selected, T-cell depleted SCT for pediatric leukemia diminishes the effect of NK alloreactivity and KIR B-content. DisclosuresNo relevant conflicts of interest to declare.

Prospective Molecular Monitoring of Minimal Residual Disease after Non-Myeloablative Allografting in Newly Diagnosed Multiple Myeloma

Background Evaluation of minimal residual disease (MRD) by molecular methods is used as a surrogate of potential eradication of myeloma cells. Prolonged high-rates of molecular remission were reported after myeloablative allografting. However, recent studies on consolidation therapy after an autograft reported 18% of PCR negativity by qualitative nested PCR and a molecular response of 63% by quantitative RQ-PCR (Ferrero et al. Leukemia 2014). The aim of our study was that of evaluating depth of response by molecular methods induced by graft-vs.-myeloma following tandem autologous/non-myeloablative allografting in newly diagnosed myeloma.Patients and Methods. Twenty-six patients enrolled in prospective clinical trials (ClinicalTrial.gov Identifier: NCT-00702247, and NCT01264315) with a diagnostic bone marrow (BM) specimen suitable for immunoglobulin heavy-chain gene rearrangement sequencing were evaluated for MRD by qualitative nested PCR and quantitative RQ-PCR. A patient specific marker was generated for 19/26 (73%). Sensitivity of nested PCR was 3 neoplastic rearrangements in 106 normal cells while each RQ-PCR showed a standard curve correlation coefficient of at least 0.95 with a slope of 3.0 to 3.9 with minimum sensitivity of 10-5 (according to Euro-MRD criteria). Transplant plan consisted of a standard autograft (melphalan 200 mg/m2) followed by 200 cGy TBI and an allograft. Post-transplant donor lymphocyte infusions or maintenance/consolidation with new drugs were not allowed until clinical relapse. BM samples were collected at diagnosis, after the autograft, at month 1, 3, 6 after the allograft and then every 6 months or as clinically indicated. MRD negativity by nested-PCR or by RQ-PCR was defined as al least two consecutive samples scored negative.Results. At a median follow-up of 11.9 years (6.1-15.2) from diagnosis and 11.0 years (5.0-14.2) from the allograft, median overall survival (OS) for the entire patient cohort was not reached and median event-free survival (EFS) was 4 years from the allograft. Overall transplant-related mortality was 11.5% at 1 year and 15.4% at 5 years. Relapse was 3.8% at 1 year, 30.8% at 3 years and 34.6% at 5 years. Cumulative incidence of acute II-IV GVHD was 26.9%. At follow up, only 2 patients were on immunosuppression for limited chronic GVHD. In the 19/26 (73%) patients with a molecular marker, the rate of nested-PCR negativity remained low at month 3 (3/19, 16%) after the allograft and gradually increased at month 6 and 12 up to 44% (8/18) and 47% (7/15) respectively. By RQ-PCR analysis, the overall tumor reduction of the whole treatment was 13.80 ln and progressively increased through the autograft, the allograft and the post-transplant period (p<0.001). After the autograft a median reduction of 4.59 ln and one month after the allograft a further decrease of 4.83 ln were observed. At month 3, MRD levels were similar to those at month 1 whereas a further decrease of 4.61 ln was observed at month 6 suggesting progressive graft-vs.-myeloma effect. At 2 years, the overall molecular response by RQ-PCR was 63%. Overall, 8 relapses occurred. Five/8 in the 11 patients who never showed a molecular response; 1 in a patient negative by RQ-PCR but positive by nested PCR. In those who reached nested PCR negativity, 1 showed molecular relapse two years before clinical relapse and 1 relapsed 8 months after the last PCR-negative sample. At median follow up, median OS and EFS were not reached in patients who achieved nested PCR negativity whereas median OS and EFS were 3.3 years and 1.5 years in the remaining patients (p 0.023 and p 0.009). Similarly, median OS and EFS were not reached in all patients who achieved a molecular response by RQ-PCR as compared with those who did not (p 0.046 and p 0.025).Conclusions.Graft-vs-myeloma after non-myeloablative allografting reported prolonged rates of qualitative (nested PCR) molecular remissions similar to those after myeloablative allografting and higher than the recently reported combination of autografting and consolidation with anti-myeloma agents. Quantitative RQ-PCR analysis showed a deeper tumor reduction after non-myeloablative allografting than consolidation with new drugs. In the light of our results, it may be ethical to evaluate the combination of graft-vs-myeloma with newer anti-myeloma agents on larger series of young high risk and early relapsed patients where life expectancy is poor also in the era of new drugs. DisclosuresNo relevant conflicts of interest to declare.

Hematopoietic SCT in Europe: data and trends in 2011.

In all, 651 from 680 centers in 48 countries reported 35 660 hematopoietic SCT (HSCT) in 32 075 patients (13 470 allogeneic (42%), 18 605 autologous (58%)) to the 2011 survey. Main indications were: leukemias; 10 113 (32% 94% allogeneic); lymphoid neoplasias; non-Hodgkin's lymphoma, Hodgkin's lymphoma, plasma cell disorders; 18 433 (57% 12% allogeneic); solid tumours; 1573 (5% 5% allogeneic); and non-malignant disorders; 1830 (6% 92% allogeneic). There were more unrelated donors than HLA identical sibling donors (54% versus 39%); proportion of peripheral blood as stem cell source was 99% for autologous and 73% for allogeneic HSCT. Cord blood was only used in allogeneic transplants (6% of total). In the past 10 years, the overall number of transplants has increased by 53%. Allogeneic HSCT have doubled (from 7272 to 14 549) while, autologous have increased by 32% and continue to increase by about 1100 HSCT per year since 2001. In the past 2 years, an increase of >2000 HSCT per year was seen. Transplant activity is shown by team size. For allogeneic HSCT, we show use of reduced-intensity conditioning versus myeloablative conditioning across Europe and use of post-transplant donor lymphocyte infusions with considerable variation across different countries.

Allogeneic haematopoietic stem cell transplantation for metastatic renal carcinoma in Europe

Background: An allogeneic antitumour effect has been reported for various cancers. We evaluated the experience of allogeneic haematopoietic stem cell transplantation (HSCT) for renal cell carcinoma (RCC) in 124 patients from 21 European centres.Patients and methods: Reduced intensity conditioning and peripheral blood stem cells from an HLA-identical sibling (n = 106), a mismatched related (n = 5), or an unrelated (n = 13) donor were used. Immunosuppression was cyclosporine alone, or combined with methotrexate or mycophenolate mofetil. Donor lymphocyte infusions (DLI) were given to 42 patients. The median follow-up was 15 (range 3–41) months.Results: All but three patients engrafted. The cumulative incidence of moderate to severe, grades II–IV acute GVHD was 40% and for chronic GVHD it was 33%. Transplant-related mortality was 16% at one year. Complete (n = 4) or partial (n = 24) responses, median 150 (range 42–600) days post-transplant, were associated with time from diagnosis to HSCT, mismatched donor and acute GVHD II-IV. Factors associated with survival included chronic GVHD (hazards ratio, HR 4.12, P < 0.001), DLI (HR 3.39, P < 0.001), <3 metastatic sites (HR 2.61, P = 0.002) and a Karnofsky score >70 (HR 2.33, P = 0.03). Patients (n = 17) with chronic GVHD and given DLI had a 2-year survival of 70%.Conclusion: Patients with metastatic RCC, less than three metastatic locations and a Karnofsky score >70% can be considered for HSCT. Posttransplant DLI and limited chronic GVHD improved the patient survival.

Increasing Donor Chimerism and Inducing Tolerance to Islet Allografts by Post-Transplant Donor Lymphocyte Infusion

Inducing donor chimerism is the most consistently successful approach to achieve transplant tolerance. We found that a low level of donor chimerism, which was induced by a relatively non-toxic approach, induced donor-specific tolerance to islet allografts in chemically induced diabetic mice. However, a similar level of donor chimerism could not protect donor islet allografts in non-obese diabetic (NOD) mice that spontaneously developed autoimmune diabetes. Rejection of donor islet allografts in diabetic NOD mice with a low level of donor chimerism was mediated by recurrent autoimmunity. We used post-transplant donor lymphocyte infusion (DLI) to increase donor chimerism and to induce tolerance to islet allografts. DLI significantly increased donor chimerism and promoted donor-specific tolerance to islet allografts in diabetic NOD mice. Self-tolerance to islet autoantigens was restored and restoring self-tolerance is mediated by immunoregulation. Thus, our data showed that adoptive immunotherapy with post-transplant DLI after establishing a low level of donor chimerism as a platform enhances donor chimerism, induces donor-specific tolerance to islet allografts and restores self-tolerance in the setting of autoimmune diabetes. Our data also showed that central tolerance is not sufficient to induce tolerance and peripheral tolerance through immunoregulation for restoring self-tolerance is required in the setting of autoimmune diabetes.

Improved Outcomes for Peripheral Blood Stem Cell Transplantation in Advanced Myelodysplastic Syndrome.

Allogeneic marrow or peripheral blood stem cell transplantation (PBSCT) is the only curative treatment for myelodysplastic syndrome (MDS). Historically, transplantation for MDS has produced long-term disease-free survival rates of 30–40%, partially due to high procedural mortality (~40%) in this patient population. Although transplant outcomes in younger patients with low-risk disease have been favorable, inferior results are seen in older patients and those with more advanced disease. Evidence suggests that the lower transplant-related mortality (TRM) and improved graft-versus-leukemia seen with PBSCT may translate into improved clinical outcomes for MDS patients. Forty-four patients, aged 12–73 years (median 50) received a PBSCT from a matched related sibling donor (MRD). Patients aged <55 years, without prohibitive comorbidity, received myeloablative conditioning consisting of total body irradiation and cyclophosphamide, followed by a T cell depleted allograft and scheduled post-transplant donor lymphocyte infusions (MST, n=23). Patients ineligible for an ablative transplant due to age or poor health received reduced intensity conditioning (fludarabine and cyclophosphamide, melphalan, or busulfan) followed by a T cell replete allograft (n=21). Six patients had low-risk MDS (RA/RARS), while the majority of patients (86%) had advanced disease (RAEB [9], RAEBT [6], AML [13], therapy-related MDS [10]). Median follow-up is 15.3 (range 2–82) months. Patients with therapy-related MDS had a significantly lower survival rate due to a very high risk of relapse (figure). The actuarial probabilities of overall survival (OS), disease-free survival (DFS), relapse, and TRM were 64%, 59%, 26%, and 23% for primary MDS patients, and 51%, 47%, 40%, and 25% for the whole cohort. Transplant-related mortality in patients under 50 years of age was 11% vs. 45% in patients ≥50 years (p=0.03). OS and DFS were significantly better in recipients of MST (64%, 57%) than in patients receiving reduced-intensity PBSCT (33%, 34%), due to a higher risk of relapse in the latter group (55% vs. 29%, p=0.10). In nineteen patients <50 years receiving MST, actuarial probability of OS, DFS, relapse, and TRM were 81%, 72%, 23%, and 7%, respectively. In summary, PBSCT yields superior outcomes for patients with primary MDS, even in patients in transformation to AML. The inferior outcomes seen in therapy-related MDS suggest alternative therapies are required for this patient population. Reduced intensity transplantation permits curative therapy for MDS patients not amenable to MST, but at the price of increased TRM and relapse in this older cohort. [Display omitted]

INDUCING DONOR-SPECIFIC TOLERANCE TO ISLET ALLOGRAFTS IN DIABETIC NOD MICE BY POSTTRANSPLANT DONOR LYMPHOCYTE INFUSION

P939 Aims: A substantial level of donor lymphocyte chimerism is required to protect donor-specific islet allografts in the mouse model with autoimmune diabetes. Donor islet allografts can be rejected in diabetic NOD mice with a low level of donor lymphocyte chimerism. In this study, we investigated whether posttransplant donor lymphocyte infusion increases donor chimerism and induces donor-specific tolerance to islet allografts in diabetic NOD mice. Methods: Donor BALB/c (H-2d) splenocytes were injected into prediabetic NOD/Lt mice (H-2g7) and diabetic NOD mice at day -3, followed by one dose of cyclophosphamide at day -1. BALB/c bone marrow cells (4x 107) were infused at day 0. Anti-CD40L mAb and rapamycin were given from day 0 to day 14. Donor islets were transplanted under left kidney capsule simultaneously with bone marrow transplantation in diabetic NOD mice. Donor lymphocyte infusion (1x107) was given in prediabetic NOD mice at 2 and 4 weeks post-bone marrow transplantation. In diabetic NOD mice, donor lymphocyte infusion (2x 107 or 3x 107) was given at 2, 4, and 6 weeks post-bone marrow transplantation. Mixed chimerism was measured by flow cytometric analysis. Islet graft function was monitored by measuring blood glucose. Left nephrectomy was performed in diabetic NOD mice with islet graft function at 100 days posttransplant. To test donor-specific tolerance, second donor-specific or third-party islets were transplanted under right kidney capsule of these NOD mice 1 week after left nephrectomy. Results: Donor lymphocyte chimerism was achieved in all prediabetic and diabetic NOD mice without or with posttransplant donor lymphocyte infusion. At 8 weeks post-bone marrow transplantation, the percentage of donor lymphocyte chimerism was 20.7±4.3% in prediabetic NOD mice without posttransplant donor lymphocyte infusion (N=11). Donor lymphocyte chimerism was significantly increased to 39.0±24.9% in prediabetic NOD mice with posttransplant donor lymphocyte infusion (N=9, P<0.05). The percentage of donor lymphocyte chimerism was 10.8±4.7% in diabetic NOD mice without posttransplant donor lymphocyte infusion (N=13). While posttransplant donor lymphocyte infusion was given, donor lymphocyte chimerism was significantly increased to 32.5±22.1% in diabetic NOD mice (N=9, P<0.05). Without posttransplant donor lymphocyte infusion, donor islet grafts survival was 30.8% in diabetic NOD mice at 100 days posttransplant (N=13). With posttransplant donor lymphocyte infusion, donor islet graft survival was 89% in diabetic NOD mice at 100 days posttransplant (N=9, P<0.01). The return of hyperglycemia in these NOD mice after nephrectomy confirmed islet graft function. Furthermore, long-term second donor-specific islet graft survival was achieved. Graft-versus-host disease was not observed in these NOD mice without or with posttransplant donor lymphocyte infusion. Conclusions: Our data demonstrate that adoptive immunotherapy with posttransplant donor lymphocyte infusion enhances donor chimerism and induces donor-specific tolerance to islet allografts in the setting of autoimmune diabetes.

Allogeneic stem-cell transplantation for lymphoproliferative disorders using BEAM–CAMPATH (± fludarabine) conditioning combined with post-transplant donor-lymphocyte infusion

We report our updated experience of allogeneic transplantation in lympho-proliferative disorders using a reduced-intensity conditioning regimen combining BEAM (plus fludarabine in three cases) with pre-transplant CAMPATH. Post-transplant donor lymphocytes have been infused for persisting disease or relapse, and both chimerism and minimal residual disease have been monitored utilizing molecular techniques. Thirty patients with median age 47.6 years underwent allogeneic transplantation for relapsed or high-risk lymphoproliferative disease using HLA-identical (sibling n = 25, unrelated n = 2) or one antigen mismatched sibling donors (n = 3). Twenty-one had NHL, three had HD and six had CLL/PLL. Stem-cell source was PBSC (n = 24), BM (n = 5) or both (n = 1) with a median CD34 dose of 4.5 x 10(6)/kg. GvHD prophylaxis was with CYA and MTX. Engraftment was prompt in the majority of patients, with a median of 15 days to both ANC > 0.5 and platelets > 20. There have been three transplant-related deaths secondary to viral pneumonitis or bacterial pneumonia. Seven patients developed Grade I-II acute GvHD post-transplant. Of 28 evaluable patients, 18 achieved a CR at assessment 2-3 months post-transplant and a further patient converted from PR to CR following DLI, to give an overall CR rate of 68%. Three patients had early progressive disease and six have relapsed from CR or progressed from PR (two of whom have achieved CR following DLI therapy). Overall survival is 67% and event-free survival 48% at 3 years. With a median follow-up of 1.3 years 57% of patients are currently alive and lymphoma-free. A molecular remission has been achieved in nine of 12 informative patients. These encouraging results show that this reduced-intensity conditioning regimen is effective, with a low-toxicity profile compared with conventional TBI-based conditioning, and certainly merits further evaluation in this setting.