Impact of Reduced-Intensity Conditioning Regimens on Outcomes in Diffuse Large B Cell Lymphoma Undergoing Allogeneic Transplantation

Outcomes of allogeneic hematopoietic stem cell transplantation for relapsed or refractory diffuse large B-cell lymphoma

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a currative treatment modality for diffuse large B-cell lymphoma (DLBCL) because of the intrinsic graft-versus-lymphoma effect. However, limited information is available regarding which patients with relapsed or refractory DLBCL are likely to benefit from allo-HSCT. We retrospectively analyzed data from 1268 DLBCL patients who received allo-HSCT. The overall survival and progression-free survival (PFS) rates were 30.3% and 21.6% at 3 years, respectively. Multivariate analysis revealed that stable or progressive disease at transplantation, male patient, poorer performance status at transplantation, and shorter intervals from previous transplantation were associated independently with a lower PFS. Four prognostic factors were used to construct a prognostic index for PFS, predicting 3-year PFS of 55.4%, 43.7%, 20.4% and 6.6%, respectively. The prognostic model predicted relapse rates following allo-HSCT accordingly (P < 0.0001), whereas did not predict transplantation-related mortality (P = 0.249). The prognostic index can identify a subgroup of DLBCL patients who benefit from allo-HSCT and it is worthwhile to evaluate whether this model is also applicable to patients undergoing allo-HSCT in cases of relapse after chimeric antigen receptor engineered T-cell therapy, although the application of allo-HSCT has been declining with the increase of novel immunotherapies.

Therapeutic options for large B-cell lymphoma relapsing after CD19-directed CAR T-cell therapy

In recent years, chimeric antigen receptor T-cell therapy (CAR T) has revolutionized the treatment landscape for large B cell lymphoma (LBCL), demonstrating remarkable efficacy and ushering a new era of therapeutic possibilities. However, a subset of patients may not achieve the desired response with CAR T. This review examines strategies aimed at optimizing outcomes for patients who relapse or progress after CAR T. Available data on utilization of CD19-directed monoclonal antibodies and antibody drug conjugates have shown limited efficacy in this setting. Moreover, bispecific antibodies have also emerged as an alternative therapy in relapsed and or refractory LBCL, but long-term follow up treated cases post-CAR T failure are lacking. Several observational studies have shown efficacy of allogeneic hematopoietic cell transplantation, but attainment of a complete remission prior to allografting is a prerequisite to achieve durable remissions. As we navigate the intricate landscape of treatment of post CAR T failure, it becomes evident that this represents a therapeutic challenge which necessitates a multifaceted approach.

Busulfan and subsequent malignancy: An evidence-based risk assessment

BACKGROUND

The incidence of secondary malignancies associated with busulfan exposure is considered low, but has been poorly characterized. Because this alkylating agent is increasingly utilized as conditioning prior to gene therapy in nonmalignant hematologic and related disorders, more precise characterization of busulfan's potential contribution to subsequent malignant risk is warranted.

PROCEDURE

We conducted a literature-based assessment of busulfan and subsequent late effects, with emphasis on secondary malignancies, identifying publications via PubMed searches, and selecting those reporting at least 3 years of follow-up.

RESULTS

We identified eight pediatric and 13 adult publications describing long-term follow-up in 570 pediatric and 2076 adult hematopoietic cell transplant (HCT) recipients. Secondary malignancies were reported in 0.5% of pediatric HCT recipients, with no cases of myelodysplastic syndrome (MDS) or acute myelocytic leukemia (AML). Fatal secondary malignancies were reported in 0.8% of 1887 evaluable adult HCT recipients, and an overall incidence of secondary malignancies of 4.8% was reported in a subset of 389 evaluable adult patients. We also reviewed long-term results from eight publications evaluating lentiviral- and human promotor-based HSC-targeted gene therapy in 215 patients with nonmalignant conditions, in which busulfan/treosulfan monotherapy or busulfan/fludarabine was the only conditioning. Two malignancies were reported in patients with sickle cell disease (SCD), one of which was potentially busulfan-related. No additional malignancies were reported in 173 patients with follow-up of 5-12 years.

CONCLUSION

The incidence of busulfan-related secondary malignancies is low, and likely to be substantially less than 1% in pediatric transplant recipients, especially those receiving busulfan monotherapy for nonmalignant conditions other than SCD.

Allogeneic hematopoietic stem cell transplantation for B-cell lymphoma in Taiwan

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is considered for patients with high-risk B-cell lymphoma and relapsed or refractory disease. This study aimed to analyze the long-term follow-up data of patients who underwent allo-HSCT in Taiwan. This was a retrospective observational study using data from the Taiwan Society of Blood and Marrow Transplantation database. A total of 105 patients who underwent allo-HSCT because of high-risk, relapsed, or refractory disease between 2010 and 2019 were included. Forty-five percent of the patients previously underwent autologous stem cell transplantation (ASCT). The median follow-up duration was 18.6 months. The probability of 3-year progression-free survival and overall survival (OS) was 34.5% and 37%, respectively. The probability of 1-year non-relapse mortality was 31.4%, and the major cause was infection (75.8%). The multivariable analysis showed that not in remission at the time of transplantation and the absence of graft-versus-host disease (GVHD) were factors associated with inferior OS. The probability of 3-year OS in patients with diffuse large B-cell lymphoma who underwent allo-HSCT and allo-HSCT after ASCT was 40.2% and 25.2%, respectively. Allo-HSCT could be a salvage therapeutic option for relapsed or refractory B-cell lymphoma. Complete remission at the time of allo-HSCT and the presence of GVHD are independent variables for overall survival.

ASTCT Clinical Practice Recommendations for Transplantation and Cellular Therapies in Diffuse Large B Cell Lymphoma

Autologous hematopoietic cell transplantation (auto-HCT) has long been the standard approach for patients with relapsed/refractory (R/R) chemosensitive diffuse large B cell lymphoma (DLBCL). However, the advent of chimeric antigen receptor (CAR) T cell therapy has caused a paradigm shift in the management of R/R DLBCL patients, especially with the recent approval of CD19-directed CAR-T therapy in the second-line setting in high-risk groups (primary refractory and early relapse [≤12 months]). Consensus on the contemporary role, optimal timing, and sequencing of HCT and cellular therapies in DLBCL is lacking; therefore, the American Society of Transplantation and Cellular Therapy (ASTCT) Committee on Practice Guidelines undertook this project to formulate consensus recommendations to address this unmet need. The RAND-modified Delphi method was used to generate 20 consensus statements with a few key statements as follows: (1) in the first-line setting, there is no role for auto-HCT consolidation for patients achieving complete remission (CR) following R-CHOP (rituximab, cyclophosphamide, adriamycin, vincristine, and prednisone) or similar therapy in non-double-hit/triple-hit cases (DHL/THL) and in DHL/THL cases receiving intensive induction therapies, but auto-HCT may be considered in eligible patients receiving R-CHOP or similar therapies in DHL/THL cases; (2) auto-HCT consolidation with thiotepa-based conditioning is standard of care for eligible patients with primary central nervous system lymphoma achieving CR with first-line therapy; and (3) in the primary refractory and early relapse setting, the preferred option is CAR-T therapy, whereas in late relapse (>12 months), consolidation with auto-HCT is recommended for patients achieving chemosensitivity to salvage therapy (complete or partial response), and CAR-T therapy is recommended for those not achieving remission. These clinical practice recommendations will serve as a tool to guide clinicians managing patients with newly diagnosed and R/R DLBCL.

The two-step approach to allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) provides the only potentially curative option for multiple hematological conditions. However, allogeneic HSCT outcomes rely on an optimal balance of effective immune recovery, minimal graft-versus-host disease (GVHD), and lasting control of disease. The quest to attain this balance has proven challenging over the past few decades. The two-step approach to HSCT was conceptualized and pioneered at Thomas Jefferson University in 2005 and remains the main platform for allografting at our institution. Following administration of the transplant conditioning regimen, patients receive a fixed dose of donor CD3+ cells (HSCT step one-DLI) as the lymphoid portion of the graft on day -6 with the aim of optimizing and controlling T cell dosing. Cyclophosphamide (CY) is administered after the DLI (days -3 and -2) to induce donor-recipient bidirectional tolerance. On day 0, a CD34-selected stem cell graft is given as the myeloid portion of the graft (step two). In this two-step approach, the stem cell graft is infused after CY tolerization, which avoids exposure of the stem cells to an alkylating agent, allowing rapid count recovery. Here, the two-step platform is described with a focus on key results from studies over the past two decades. Finally, this review details lessons learned and current strategies to optimize the graft-versus-tumor effect and limit transplant-related toxicities.

CD3-immunotoxin mediated depletion of T cells in lymphoid tissues of rhesus macaques

Selective T-cell depletion prior to cell or organ transplantation is considered a preconditioning regimen to induce tolerance and immunosuppression. An immunotoxin consisting of a recombinant anti-CD3 antibody conjugated with diphtheria toxin was used to eliminate T-cells. It showed significant T-cell depletion activity in the peripheral blood and lymph nodes in animal models used in previous studies. To date, a comprehensive evaluation of T-cell depletion and CD3 proliferation for all lymphoid tissues has not been conducted. Here, two rhesus macaques were administered A-dmDT390-SCFBdb (CD3-IT) intravenously at 25 μg/kg twice daily for four days. Samples were collected one day prior to and four days post administration. Flow cytometry and immunofluorescence staining were used to evaluate treatment efficiency accurately. Our preliminary results suggest that CD3-IT treatment may induce higher depletion of CD3 and CD4 T-cells in the lymph nodes and spleen, but is ineffective in the colon and thymus. The data showed a better elimination tendency of CD4 T-cells in the B-cell zone relative to the germinal center in the lymph nodes. Further, CD3-IT treatment may lead to a reduction in germinal center T follicular helper CD4 cells in the lymph nodes compared to healthy controls. The number of proliferating CD3 T-cell indicated that repopulation in different lymphoid tissues may occur four days post treatment. Our results provide insights into the differential efficacy of CD3-IT treatment and T-cell proliferation post treatment in different lymphoid tissues. Overall, CD3-IT treatment shows potential efficacy in depleting T-cells in the periphery, lymph nodes, and spleen, making it a viable preconditioning regimen for cell or organ transplantation. Our pilot study provides critical descriptive statistics and can contribute to the design of larger future studies.

Risk factors for fatal cardiac complications after allogeneic hematopoietic cell transplantation: Japanese Society for Transplantation and Cellular Therapy transplant complications working group

Fatal cardiac complications can occur from the early to late phases after hematopoietic cell transplantation (HCT). Herein, the Japanese transplant registry database was used to retrospectively analyze health records of 33,791 allogeneic HCT recipients to elucidate the pathogenesis and risk factors involved. Overall, 527 patients died of cardiac complications at a median of 130 (range 0-3924) days after HCT. The cumulative incidence of fatal cardiac complications was 1.2% (95% confidence interval [CI]: 1.0-1.3) and 1.6% (95% CI: 1.5-1.8) at 1 and 5 years after HCT, respectively. Fatal cardiovascular events were significantly associated with an HCT-specific comorbidity index (HCT-CI) score of ≥1 specific to the three cardiovascular items, lower performance status, conditioning regimen cyclophosphamide dose of >120 mg/kg, and female sex. Cardiovascular death risk within 60 days after HCT was associated with the type of conditioning regimen, presence of bacterial or fungal infections at HCT, and number of blood transfusions. Contrastingly, late cardiovascular death beyond 1 year after HCT was associated with female sex and older age. Lower performance status and positive cardiovascular disease-related HCT-CI were risk factors for cardiac complications in all phases after HCT. Systematic follow-up may be necessary according to the patients' risk factors and conditions.

How I treat refractory/relapsed diffuse large B-cell lymphomas with CD19-directed chimeric antigen receptor T cells

Chimeric antigen receptor (CAR) T cells targeting CD19 represent a promising salvage immunotherapy for relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL), offering ~40% of long-term responses. In everyday clinical practice, haematologists involved in CAR T cell treatment of patients with R/R DLBCL have to deal with diagnostically complex cases and difficult therapeutic choices. The availability of novel immunotherapeutic agents for R/R DLBCL and recent advances in understanding CAR T-cell failure mechanisms demand a rational approach to identify the best choice for bridging therapy and managing post-CAR T-cell therapy relapses. Moreover, positron emission tomography/computerised tomography may result in false-positive interpretation, highlighting the importance of post-treatment biopsy. In this review, we discuss all above issues, presenting four instructive cases, with the aim to provide criteria and new perspectives for CAR T-cell treatment of DLBCL.

Allogeneic Hematopoietic Cell Transplantation after Chimeric Antigen Receptor T Cell Therapy in Large B Cell Lymphoma

Anti-CD19 chimeric antigen receptor T cell (CAR-T) therapy has transformed the care of patients with relapsed/refractory large B cell lymphoma (LBCL). However, approximately 60% of CAR-T recipients ultimately will experience disease recurrence or progression. Salvage therapies after CAR-T treatment failures are of limited efficacy and have a short duration of response. The objective of the present study was to evaluate the role of allogeneic hematopoietic cell transplantation (allo-HCT) after CAR-T therapy in LBCL patients. This was a multicenter observational study reporting the outcome of 39 adult LBCL patients who underwent allo-HCT following anti-CD19 CAR-T therapy. The median patient age was 47 years (range, 20 to 68 years). HLA-matched sibling, HLA-matched unrelated, and alternative donors were used in 36%, 36%, and 28% of transplantations, respectively. Conditioning regimens were primarily of low or intermediate intensity. Disease status at allo-HCT was complete response in 41%, partial response in 38%, and progressive disease in 21%. Allo-HCT was performed at a median of 127 days (range, 82 to 206 days) after CAR-T therapy. A high incidence of hepatic toxicity (28%), including sinusoidal obstruction syndrome (15.4%; 95% confidence interval; [CI], 6.2% to 28.5%), was observed. The 1-year cumulative incidence of grade II-IV and grade III-IV acute graft-versus-host disease (GVHD) was 38.5% (95% CI, 23.2% to 53.6%) and 15.4% (95% CI, 6.1% to 28.5%), respectively. The 2-year cumulative incidence of moderate-severe chronic GVHD was 11.1% (95% CI, 3.3% to 24.3%). Overall, 2-year nonrelapse mortality and relapse/progression incidence were 26% (95% CI, 13% to 41%) and 43% (95% CI, 27% to 59%), respectively. With a median follow-up of 32 months, the 2-year overall survival (OS) and progression-free survival (PFS) were 45% (95% CI, 31% to 66%) and 31% (95% CI, 19% to 50%), respectively. In multivariable analyses, pre-HCT elevated lactate dehydrogenase level and transformed lymphoma were predictive of OS and PFS, respectively. Our data suggest that allo-HCT after anti-CD19 CAR-T treatment failure is feasible with a relatively promising efficacy but possibly high toxicity rate.

Allogeneic transplant following CAR T-cell therapy for large B-cell lymphoma

Allogeneic hematopoietic cell transplantation (alloHCT) can potentially salvage large B-cell lymphoma (LBCL) patients experiencing treatment failure after chimeric antigen receptor T-cell therapy (CAR T). Nonetheless, data on the efficacy and toxicities of alloHCT after receipt of CAR T are limited. We report a multicenter retrospective study assessing the safety, toxicities, and outcomes of alloHCT in LBCL patients following CAR T failure. Eighty-eight patients with relapsed, refractory LBCL received an alloHCT following anti-CD19 CAR T failure. The median number of lines of therapy between CAR T infusion and alloHCT was one (range, 0-7). Low intensity conditioning was used in 77% (n=68) and peripheral blood was the most common graft source (86%, n=76). The most common donor types were matched unrelated donor (39%), followed by haploidentical (30%) and matched related donor (26%). Median follow-up of survivors was 15 months (range, 1-72). One-year overall survival, progression-free survival, and graft-versus-host disease-free relapse-free survival were 59%, 45%, and 39% respectively. One-year non-relapse mortality and progression/relapse were 22% and 33% respectively. On multivariate analysis, <2 lines of intervening therapy between CAR T and alloHCT and complete response at time of alloHCT were associated with better outcomes. In conclusion, alloHCT after CAR T failure can provide durable remissions in a subset of patients.

Impact of conditioning regimen intensity on the outcomes of peripheral T-cell lymphoma, anaplastic large cell lymphoma and angioimmunoblastic T-cell lymphoma patients undergoing allogeneic transplant

There have been no large studies comparing reduced-intensity/non-myeloablative conditioning (RIC/NMA) to myeloablative conditioning (MAC) regimens in T-cell non-Hodgkin lymphoma (T-NHL) patients undergoing allogeneic transplant (allo-HCT). A total of 803 adults with peripheral T-cell lymphoma, anaplastic large cell lymphoma and angioimmunoblastic T-cell lymphoma (age 18-65 years), undergoing allo-HCT between 2008-2019 and reported to the Center for International Blood and Marrow Transplant Research with either MAC (n = 258) or RIC/NMA regimens (n = 545) were evaluated. There were no significant differences between the two cohorts in terms of patient sex, race and performance scores. Significantly more patients in the RIC/NMA cohort had peripheral blood grafts, haematopoietic cell transplantation-specific comorbidity index (HCT-CI) of ≥3 and chemosensitive disease compared to the MAC cohort. On multivariate analysis, overall survival (OS) was not significantly different in the RIC/NMA cohort compared to the MAC cohort (hazard ratio (HR) = 1.01, 95% confidence interval (CI) = 0.79-1.29; p = 0.95). Similarly, non-relapse mortality (NRM) (HR = 0.85, 95% CI = 0.61-1.19; p = 0.34), risk of progression/relapse (HR = 1.29; 95% CI = 0.98-1.70; p = 0.07) and therapy failure (HR = 1.14; 95% CI = 0.92-1.41, p = 0.23) were not significantly different between the two cohorts. Relative to MAC, RIC/NMA was associated with a significantly lower risk of grade 3-4 acute graft-versus-host disease (HR = 0.67; 95% CI = 0.46-0.99, p = 0.04). Among chemorefractory patients, there was no difference in OS, therapy failure, relapse, or NRM between RIC/NMA and MAC regimens. In conclusion, we found no association between conditioning intensity and outcomes after allo-HCT for T-cell NHL.

The Two-Step Allogeneic Stem Cell Transplant Approach Results in Rapid Engraftment and Excellent Outcomes in Patients with Lymphoid Malignancies

The two-step graft engineering approach has been the main platform for allogeneic hematopoietic cell transplantation (allo-HCT) at Thomas Jefferson University since 2005. We have previously described separating donor lymphocytes infusion followed by cyclophosphamide for bidirectional tolerization from CD34-selected hematopoietic grafts in haploidentical and matched related donors. We analyzed 60 patients with high-risk lymphoid malignancies who underwent a two-step allo-HCT from 2008-2020. The majority of patients received haploidentical (82%) and (20%) patients received matched related stem cell grafts. Patients underwent transplant for DLBCL (n = 17, 28%), CLL (n = 10, 17%), follicular lymphoma (n=8, 13%), and Hodgkin lymphoma (n = 7, 12%). Eight patients (13%) had prior high dose chemotherapy. Thirty patients (50%) had HCT-CI ≥ 3; 20 patients (33%) had CIBMTR RDRI high or very high-risk disease. The median age for the group was 56 years (range 24-75). Neutrophils engrafted at a median of 11 days (range from 9 to 16 days) and platelets engrafted at a median of 16 days (range from 13 to 37 days). With a median follow up of six years, the 3-year probability of overall survival and disease-free survival were 62.9% (95% confidence interval is 49.3% to 73.8%) and 60.2% (95% confidence interval is 46.4% to 71.6%) respectively. The cumulative incidence of relapse at 3 years was 11.9% (confidence interval 0.052-0.216). The cumulative incidence of non-relapse mortality at 3 years was 30.1% (confidence interval 0.191-0.420). The cumulative incidence of grade 2-4 acute GVHD at one year was 45% (95% confidence interval 0.322 to 0.570). The cumulative incidence of grade 3-4 acute GVHD at one year was 5% (95% confidence interval 0.013 to 0.126). The cumulative incidence of cGVHD at 3 years was 15.2% (95% confidence interval 0.075 to 0.254). In conclusion, the two-step approach achieved excellent outcomes in high-risk lymphoid malignancies with rapid neutrophil and platelet recovery.

Allogeneic Transplant and CAR-T Therapy After Autologous Transplant Failure in DLBCL: A Noncomparative Cohort Analysis

Allogeneic transplant (alloHCT) and chimeric antigen receptor modified (CAR) T-cell therapy are potentially cuarative options of diffuse large B-cell lymphoma (DLBCL) relapsing after an autologous (auto) HCT. While the Center for International Blood and Marrow Transplant Research (CIBMTR) prognostic model can predict outcomes of alloHCT in DLBCL after autoHCT failure, corresponding models of CAR-T treatment in similar patient populations are not available. In this noncomparative registry analysis we report outcomes of DLBCL patients (≥18 years), undergoing a reduced intensity alloHCT or CAR-T therapy during 2012-2019, after a prior auto-HCT failure, and apply CIBMTR prognostic model to CAR-T recipients. 584 patients were included. The 1-year relapse, non-relapse mortality, overall survival (OS) and progression-free survival (PFS) for CAR-T treatment after autoHCT failure were were 39.5%, 4.8%, 73.4% and 55.7%, respectively. The corresponding rates in alloHCT cohort were 26.2%, 20.0%, 65.6% and 53.8%, respectively. The 1-year OS of alloHCT recipients classified as low-, intermediate- and high/very high-risk groups according to the CIBMTR prognostic score was 73.3%, 59.9%, and 46.3, respectively (p=0.002). The corresponding rates for low-, intermediate- and high/very high-risk CAR-T patients were 88.4%, 76.4%, and 52.8%, respectively (p<0.001). This registry analysis shows that both CAR-T and alloHCT can provide durable remissions in subset of DLBCL patients relapsing after a prior autoHCT. The simple, CIBMTR prognostic score can be used to identify patients at high risk of treatment failure after either procedure. Evaluation of novel relapse mitigations strategies after cellular immunotherapies are warranted in these high risk patients.

The evolving role of allogeneic haematopoietic cell transplantation in the era of chimaeric antigen receptor T-cell therapy

Chimaeric antigen receptor T-cell (CAR T) therapy has revolutionized the management of many haematological malignancies. It is associated with impressive disease responses in relapsed or refractory high-grade B-cell non-Hodgkin lymphoma (B-NHL) and acute lymphoblastic leukaemia (B-ALL) with durable remissions in a subset of patients. Historically, haematopoietic cell transplantation (HCT) has been the standard consolidation strategy for many of these patients who are now being treated with CAR T. Relapses are frequent after CD19 CAR T therapy in B-ALL and consolidation with allogeneic HCT (allo-HCT) may improve survival of patients with high-risk disease. There appears to be a clear difference in B-ALL outcomes between paediatric and adult patients, with the latter having a much higher risk of relapse after CAR T therapy. Late relapses are infrequent in patients with B-NHL and consolidation with allo-HCT may not be needed in patients who achieve a complete remission after CAR T therapy. Future registry-based and prospective studies will hopefully provide the needed data in the future to risk-stratify the recipients of CAR T therapy. Meanwhile, we provide guidance on patient selection and practical issues with performing allo-HCT after CAR T therapy.