Allogeneic hematopoietic cell transplantation after failed autologous transplant for lymphoma using TLI and anti-thymocyte globulin conditioning

The significance of mixed chimaerism and cell lineage chimaerism monitoring in paediatric patients post haematopoietic stem cell transplant

Haematopoietic stem cell transplants (HSCTs) are carried out across the world to treat haematological and immunological diseases which would otherwise prove fatal. Certain diseases are predominantly encountered in paediatric patients, such severe primary immunodeficiencies (PID) and diseases of inborn errors of metabolism (IEM). Chimaerism testing for these disorders has different considerations compared to adult diseases. This review focuses on the importance of cell-lineage-specific chimaerism testing and examines the appropriate cell populations to be assessed in individual paediatric patient groups. By analysing disease-associated subpopulations, abnormalities are identified significantly earlier than in whole samples and targeted clinical decisions can be made. Chimaerism methods have evolved over time and lead to an ever-increasing level of sensitivity and biomarker arrays to distinguish between recipient and donor cells. Short tandem repeat (STR) is still the gold standard for routine chimaerism assessment, and hypersensitive methods such as quantitative and digital polymerase chain reaction (PCR) are leading the forefront of microchimaerism testing. The rise of molecular methods operating with minute DNA amounts has been hugely beneficial to chimaerism testing of paediatric samples. As HSCTs are becoming increasingly personalised and risk-adjusted towards a child's individual needs, chimaerism testing needs to adapt alongside these medical advances ensuring the best possible care.

Outcomes of hematopoietic cell transplantation for transformed follicular lymphoma

This study characterized the outcomes of patients who underwent hematopoietic cell transplantation (HCT) for transformed follicular lymphoma (tFL), and clarified the association of low-dose anti-thymocyte globulin use with outcomes after allogeneic HCT. The retrospective study cohort included 74 consecutive patients who underwent autologous (n = 23) or allogeneic (n = 51) HCT at our center from 2000 to 2017. Compared with the allogeneic HCT group, the autologous HCT group underwent fewer systemic regimens before HCT (median 2 vs. 5, p < 0.001) and were more likely to have chemosensitive disease at HCT (100% vs. 82%, p = 0.05), while age, sex and HCT-specific comorbidity index were similar between the two groups. With a median follow-up of 5.8 years among survivors, the 5-year probability of progression-free survival was 64% after autologous HCT and 55% after allogeneic HCT (p = 0.21). The 5-year cumulative incidence of non-relapse mortality was 0% after autologous HCT and 9.5% after allogeneic HCT (p = 0.062). The 5-year cumulative incidence of disease progression was similar between autologous and allogeneic HCT (36% vs. 36%, respectively, p = 0.88). In the allogeneic HCT group, the use of low-dose anti-thymocyte globulin was associated with a lower incidence of severe acute GVHD but not with an increased risk of mortality or disease progression. More than half of patients with early phase chemosensitive tFL and approximately half of those with advanced-phase tFL achieved long-term progression-free survival with autologous and allogeneic HCT, respectively. Disease progression was the major cause of treatment failure after both types of HCT. Further strategies are needed to reduce the risk of disease progression.

Safety and efficacy of a nonmyeloablative pretransplant conditioning regimen using total lymphoid irradiation with volumetric modulated arc therapy in healthy dogs: A pilot study

Allogeneic hematopoietic cell transplantation (HCT) has been an effective treatment for human patients with haematological malignancies (Baron & Storb, 2006; Bair et al., 2020; Copelan et al., 2019). However, the optimal pretransplant conditioning treatment is unclear in canine allogeneic HCT. This pilot study aimed to evaluate the safety and efficacy of total lymphoid irradiation (TLI) with volumetric modulated arc therapy (VMAT) for a nonmyeloablative HCT conditioning. Six healthy dogs were treated with 8 or 12 Gy TLI using VMAT. Haematological and physical changes were recorded over 8 weeks. To assess the effect of peripheral lymphocyte condition, lymphocyte subset and proliferative ability were examined. At the end of the experiment, necropsy was performed. All dogs showed mild‐to‐moderate neutropenia and thrombocytopenia, and these haematological changes resolved spontaneously. One dog treated with 8 Gy TLI developed transient cutaneous infection. No major complication was seen in the other seven dogs. Myelocytes and erythroblast cytopenia of bone marrow were detected in two dogs treated with 12 Gy TLI. This study is the first report of TLI using VMAT in dogs, and results suggest that this regimen is a feasible nonmyeloablative treatment.

Safety and Efficacy of Consolidation Therapy with Ipilimumab Plus Nivolumab after Autologous Stem Cell Transplantation

Autologous hematopoietic stem cell transplantation (ASCT) is a standard-of-care treatment for many hematologic malignancies. Progression of disease after ASCT is the primary cause of treatment failure. In this Phase Ib trial, we studied the safety and clinical effect of combined checkpoint inhibition therapy (CPIT) with ipilimumab and nivolumab as a consolidation strategy after ASCT for patients with high-risk diffuse large B cell lymphoma (DLBCL), mature T cell lymphoma (TCL), and multiple myeloma (MM). Starting at 14 to 28 days after ASCT, patients received ipilimumab (1 mg/kg i.v. on day 1 of weeks 1, 4, 7, 10, 16, and 22) and nivolumab (3 mg/kg i.v. on day 1 of weeks 1, 4, 7, 10, 12, 14, 16, 18, 20, 22, 24, and 26). Patients received a median of 5 doses of ipilimumab and 8 doses of nivolumab. Thirty-five patients were included in the intent-to-treat population. Ninety-four percent of the patients experienced immune-related adverse events (irAEs) of any grade. Ninety-seven percent of irAEs resolved spontaneously or after holding study drugs and instituting high-dose corticosteroid therapy. Progression-free and overall survival at 18 months post-ASCT for each disease cohort were 85.7% and 100% for primary refractory DLBCL, 28.6% and 57.1% for relapsed DLBCL, not evaluable and 80% for frontline TCL, 25% and 75% for relapsed TCL, 57.1% and 87% for high-risk transplant-naïve MM, and 40% and 100% for MM relapsed within 3 years of first ASCT. We conclude that combined CPIT appears to be tolerable as a consolidation strategy after ASCT and in addition to the potential clinical efficacy observed in some subsets of disease, T cell receptor repertoire, T regulatory cell phenotype, and gut microbiota profiles provide a biologic rationale warranting further study of this approach.

Nonmyeloablative TLI-ATG conditioning for allogeneic transplantation: mature follow-up from a large single-center cohort

Nonmyeloablative total lymphoid irradiation and antithymocyte globulin (TLI-ATG) conditioning is protective against graft-versus-host disease (GVHD), while retaining graft-versus-tumor activity across various hematologic malignancies. We report our comprehensive experience using TLI-ATG conditioning in 612 patients with hematologic malignancies who underwent allogeneic transplantation at Stanford University from 2001 to 2016. All patients received granulocyte colony-stimulating factor-mobilized peripheral blood grafts and cyclosporine and mycophenolate mofetil for GVHD prophylaxis. The median age was 60 years (range, 21-78), with a median follow-up of 6.0 years (range, 1.0-16.4). Common diagnoses included acute myeloid leukemia (AML; n = 193), myelodysplastic syndrome (MDS; n = 94), chronic lymphocytic leukemia (CLL; n = 80), non-Hodgkin lymphoma (NHL; n = 175), and Hodgkin lymphoma (HL; n = 35). Thirty-four percent of patients had a comorbidity index ≥3, 30% had a high to very high disease risk index, and 56% received unrelated donor grafts, including 15% with HLA-mismatched donors. Ninety-eight percent underwent transplant in the outpatient setting, and 57% were never hospitalized from days 0 through 100. The 1-year rates of nonrelapse mortality (NRM), grade II-IV acute GVHD, and extensive chronic GVHD were 9%, 14%, and 22%, respectively. The 4-year estimates for overall and progression-free survival were 42% and 32% for AML, 30% and 21% for MDS, 67% and 43% for CLL, 68% and 45% for NHL, and 78% and 49% for HL. Mixed chimerism correlated with the risk of relapse. TLI-ATG conditioning was well tolerated, with low rates of GVHD and NRM. Durable remissions were observed across hematologic malignancies, with particularly favorable outcomes for heavily pretreated lymphomas. Several efforts are underway to augment donor chimerism and reduce relapse rates while maintaining the favorable safety and tolerability profile of this regimen.

HLA-mismatched unrelated donor transplantation using TLI-ATG conditioning has a low risk of GVHD and potent antitumor activity

Many patients lack a fully HLA-matched donor for hematopoietic cell transplantation (HCT), and HLA mismatch is typically associated with inferior outcomes. Total lymphoid irradiation and antithymocyte globulin (TLI-ATG) is a nonmyeloablative conditioning regimen that is protective against graft-versus-host disease (GVHD), and we hypothesized that the protective effect would extend beyond HLA-matched donors. We report outcomes for all consecutively transplanted patients at Stanford University from December 2001 through May 2015 who received TLI-ATG conditioning and HCTs from 8 to 9 out of 10 HLA-mismatched unrelated donors (MMUDs, N = 72) compared with 10 out of 10 HLA-matched unrelated donors (MUDs, N = 193). The median age of the patients was 60 years with a median follow-up of 2 years, and there was a similar distribution of lymphoid and myeloid malignancies in both cohorts. There were no significant differences between MMUD and MUD cohorts in overall survival (46% vs 46% at 5 years, P = .86), disease-free survival (38% vs 28% at 5 years, P = .25), nonrelapse mortality (17% vs 12% at 2 years, P = .34), acute GVHD grades III-IV (6% vs 3% at day +100, P = .61), or chronic GVHD (39% vs 35% at 5 years, P = .49). There was a trend toward less relapse in the MMUD cohort (45% vs 60% at 5 years, hazard ratio: 0.71, P = .094), which was significant for patients with lymphoid malignancies (29% vs 57% at 5 years, hazard ratio: 0.55, P = .044). Achieving full donor chimerism was strongly associated with lower relapse rates. TLI-ATG conditioning may overcome the traditionally poorer outcome associated with HLA-mismatched donors and may be particularly well suited for patients with lymphoid malignancies who lack HLA-matched donors.

Outcomes of diffuse large B-cell lymphoma patients relapsing after autologous stem cell transplantation: an analysis of patients included in the CORAL study

In the CORAL study, 255 chemosensitive relapses with diffuse large B-cell lymphoma (DLBCL) were consolidated with autologous stem cell transplantation (ASCT), and 75 of them relapsed thereafter. The median time between ASCT and progression was 7.1 months. The median age was 56.1 years; tertiary International Prognosis Index (tIPI) observed at relapse was 0-2 in 71.6% of the patients and >2 in 28.4%. The overall response rate to third-line chemotherapy was 44%. The median overall survival (OS) was 10.0 months (median follow-up: 32.8 months). Thirteen patients received an allogeneic SCT, and three a second ASCT. The median OS was shorter among patients who relapsed <6 months (5.7 months) compared with those relapsing ⩾12 months after ASCT (12.6 months, P=0.0221). The median OS in patients achieving CR, PR or no response after the third-line regimen was 37.7 (P<0.0001), 10.0 (P=0.03) and 6.3 months, respectively. The median OS varied according to tIPI: 0-2: 12.6 months and >2: 5.3 months (P=0.0007). In multivariate analysis, tIPI >2, achievement of response and remission lasting <6 months predicted the OS. This report identifies the prognostic factors for DLBCL relapsing after ASCT and thus helps to select patients for experimental therapy.