Decade-long leukaemia remissions with persistence of CD4+ CAR T cells.

The adoptive transfer of T lymphocytes reprogrammed to target tumour cells has demonstrated potential for treatment of various cancers1-7. However, little is known about the long-term potential and clonal stability of the infused cells. Here we studied long-lasting CD19-redirected chimeric antigen receptor (CAR) T cells in two patients with chronic lymphocytic leukaemia1-4 who achieved a complete remission in 2010. CAR T cells remained detectable more than ten years after infusion, with sustained remission in both patients. Notably, a highly activated CD4+ population emerged in both patients, dominating the CAR T cell population at the later time points. This transition was reflected in the stabilization of the clonal make-up of CAR T cells with a repertoire dominated by a small number of clones. Single-cell profiling demonstrated that these long-persisting CD4+ CAR T cells exhibited cytotoxic characteristics along with ongoing functional activation and proliferation. In addition, longitudinal profiling revealed a population of gamma delta CAR T cells that prominently expanded in one patient concomitant with CD8+ CAR T cells during the initial response phase. Our identification and characterization of these unexpected CAR T cell populations provide novel insight into the CAR T cell characteristics associated with anti-cancer response and long-term remission in leukaemia.

Blinatumomab for MRD-Negative Acute Lymphoblastic Leukemia in Adults.

BACKGROUND: Many older adults with B-cell precursor acute lymphoblastic leukemia (BCP-ALL) have a relapse despite having a measurable residual disease (MRD)-negative complete remission with combination chemotherapy. The addition of blinatumomab, a bispecific T-cell engager molecule that is approved for the treatment of relapsed, refractory, and MRD-positive BCP-ALL, may have efficacy in patients with MRD-negative remission. METHODS: In a phase 3 trial, we randomly assigned patients 30 to 70 years of age with BCR::ABL1-negative BCP-ALL (with :: indicating fusion) who had MRD-negative remission (defined as <0.01% leukemic cells in bone marrow as assessed on flow cytometry) after induction and intensification chemotherapy to receive four cycles of blinatumomab in addition to four cycles of consolidation chemotherapy or to receive four cycles of consolidation chemotherapy alone. The primary end point was overall survival, and relapse-free survival was a secondary end point. RESULTS: The data and safety monitoring committee reviewed the results from the third efficacy interim analysis and recommended that they be reported. Complete remission with or without full count recovery was observed in 395 of 488 enrolled patients (81%). Of the 224 patients with MRD-negative status, 112 were assigned to each group. The characteristics of the patients were balanced between the groups. At a median follow-up of 43 months, an advantage was observed in the blinatumomab group as compared with the chemotherapy-only group with regard to overall survival (at 3 years: 85% vs. 68%; hazard ratio for death, 0.41; 95% confidence interval [CI], 0.23 to 0.73; P = 0.002), and the 3-year relapse-free survival was 80% with blinatumomab and 64% with chemotherapy alone (hazard ratio for relapse or death, 0.53; 95% CI, 0.32 to 0.87). A higher incidence of neuropsychiatric events was reported in the blinatumomab group than in the chemotherapy-only group. CONCLUSIONS: The addition of blinatumomab to consolidation chemotherapy in adult patients in MRD-negative remission from BCP-ALL significantly improved overall survival. (Funded by the National Institutes of Health and others; E1910 ClinicalTrials.gov number, NCT02003222.).

Approval of brexucabtagene autoleucel for adults with relapsed and refractory acute lymphocytic leukemia.

In October 2021, brexucabtagene autoleucel became the first anti-CD19 chimeric antigen receptor T-cell product to receive approval from the Food and Drug Administration to treat adults with relapsed and refractory B-cell acute lymphoblastic leukemia. The approval is based on results from the Zuma-3 trial and significantly widens treatment options for this patient population. In this article, we review outcomes from this study and its implications.

Modulation of the gut microbiota engages antigen cross-presentation to enhance antitumor effects of CAR T cell immunotherapy.

Several studies have shown the influence of commensal microbes on T cell function, specifically in the setting of checkpoint immunotherapy for cancer. In this study, we investigated how vancomycin-induced gut microbiota dysbiosis affects chimeric antigen receptor (CAR) T immunotherapy using multiple preclinical models as well as clinical correlates. In two murine tumor models, hematopoietic CD19+-A20 lymphoma and CD19+-B16 melanoma, mice receiving vancomycin in combination with CD19-directed CAR T cell (CART-19) therapy displayed increased tumor control and tumor-associated antigens (TAAs) cross-presentation compared with CART-19 alone. Fecal microbiota transplant from human healthy donors to pre-conditioned mice recapitulated the results obtained in naive gut microbiota mice. Last, B cell acute lymphoblastic leukemia patients treated with CART-19 and exposed to oral vancomycin showed higher CART-19 peak expansion compared with unexposed patients. These results substantiate the role of the gut microbiota on CAR T cell therapy and suggest that modulation of the gut microbiota using vancomycin may improve outcomes after CAR T cell therapy across tumor types.

Real-world effectiveness of intensive chemotherapy with 7&3 versus venetoclax and hypomethylating agent in acute myeloid leukemia.

Intensive chemotherapy with cytarabine and anthracycline (7&3) remains the standard therapy for patients medically fit for induction, but the assessment of fitness remains controversial. Venetoclax and hypomethylating agent (ven/HMA) combination therapy has improved outcomes in unfit patients but no prospective study has assessed ven/HMA versus 7&3 as initial therapy in older, fit patients. Given no studies and expectation of ven/HMA use in patients outside of trial criteria, we evaluated retrospective outcomes among newly diagnosed patients. A nationwide electronic health record (EHR)-derived database and the University of Pennsylvania EHR identified 312 patients receiving 7&3 and 488 receiving ven/HMA who were 60-75 years old without history of organ failure. Ven/HMA patients were older and more likely to have secondary AML, adverse cytogenetics, and adverse mutations. Median overall survival (OS) for patients receiving intensive chemotherapy was 22 versus 10 months for ven/HMA (HR 0.53, 95% CI 0.40-0.60). Controlling for measured baseline characteristic imbalances reduced survival advantage by half (HR 0.71, 95% CI 0.53-0.94). A sub-group of patients with equipoise, likelihood at least 30%-70% of receiving either treatment, had similar OS outcomes (HR 1.10, 95% CI 0.75-1.6). Regarding safety outcomes, 60-day mortality was higher for ven/HMA (15% vs. 6% at 60 days) despite higher documented infections and febrile neutropenia for 7&3. In this multicenter real-word dataset, patients selected for intensive chemotherapy had superior OS but a large group had similar outcomes with ven/HMA. Prospective randomized studies, controlling for both measured and unmeasured confounders, must confirm this outcome.

Central line-associated Rhizobium radiobacter bloodstream infection in two allogeneic hematopoietic cell transplant recipients.

INTRODUCTION: Rhizobium radiobacter is a gram-negative, opportunistic phytopathogen that rarely causes human infections. We report two cases of Rhizobium radiobacter central line-associated bloodstream infection (CLABSI) in allogeneic hematopoietic cell transplantation (alloHCT) recipients. We review previous reports and common microbiological characteristics associated with this organism. CASE REPORTS: Two adult males developed R. radiobacter CLABSIs at day +81 and day +77 post-alloHCT. Patient one was asymptomatic on presentation while patient two was febrile. One patient had a polymicrobial infection, which has not been previously described. The presence of high-level ceftazidime resistance in both patients suggests third-generation cephalosporin resistance may be more common than previously recognized. MANAGEMENT AND OUTCOME: For both patients, microbiologic clearance was achieved through peripherally inserted central catheter removal and initiation of intravenous cefepime. Antibiotic therapy was narrowed to oral levofloxacin for a total 14-day course from the time of first negative blood culture. There has been no subsequent recurrence of R. radiobacter infection at 12 and 5 months of follow-up for patients one and two, respectively. DISCUSSION: These two cases add to the scant literature characterizing R. radiobacter infection following alloHCT. Immunosuppressive agents for graft-versus-host disease prophylaxis may have predisposed these patients to R. radiobacter infection. Our reports, and previously reported cases, suggest R. radiobacter exhibits low virulence, mild symptom burden, and does not confer a high mortality risk. In the alloHCT setting, further accumulation of cases is needed to aid in understanding clinical features and characteristics of R. radiobacter infection.

One versus two sets of busulfan therapeutic drug monitoring in myeloablative allogeneic hematopoietic cell transplant.

INTRODUCTION: Busulfan is a common component of allogeneic hematopoietic cell transplant (alloHCT) conditioning, however interpatient pharmacokinetic variability can result in enhanced toxicity or increased relapse risk. Therapeutic drug monitoring (TDM) can minimize variability, yet the optimal frequency of TDM is unknown. We compared outcomes for patients with one versus two sets of busulfan TDM during myeloablative conditioning (MAC) prior to alloHCT. METHODS: We analyzed the impact of busulfan TDM frequency and dose adjustments, with the primary outcome being relapse-free survival (RFS). Other outcomes included the incidence of acute and chronic graft versus host disease (GVHD), oral mucositis, pulmonary toxicity, sinusoidal obstruction syndrome (SOS), the cumulative incidence of relapse (CIR), and overall survival (OS). RESULTS: Twenty-two patients underwent one set of sampling while 53 patients underwent two sets. Similar baseline characteristics were observed between the groups. There were no significant differences observed in RFS by day +180 (77.3% vs. 79.2%, p = 1.0), CIR by day +180 (18.2% vs. 17.8%, p = 0.74), or OS (p = 0.73). The incidences of acute GVHD, chronic GVHD, SOS, and severe mucositis were also similar. In each group, 63% received busulfan dose adjustments after one set, with 52.8% receiving further dose adjustments following the second set. CONCLUSION: We observed no significant difference in alloHCT outcomes between patients who underwent one versus two sets of busulfan TDM sampling, suggesting that a single-time TDM and dose adjustment may be adequate to maximize outcomes after MAC alloHCT.

Day 4 vs. day 12 G-CSF administration following reduced intensity peripheral blood allogeneic stem cell transplant.

INTRODUCTION: Granulocyte colony-stimulating factor (G-CSF) hastens neutrophil engraftment and reduces infections after allogeneic hematopoietic cell transplant (alloHCT), yet the optimal start date is unknown. Additionally, concurrent G-CSF and methotrexate for graft-vs-host disease (GVHD) prophylaxis may potentiate myelosuppression, and prolonged G-CSF is costly. Our institution changed from day + 4 to day + 12 G-CSF initiation following reduced intensity (RIC) alloHCT with methotrexate GVHD prophylaxis. METHODS: We retrospectively compared day + 4 and day + 12 G-CSF initiation after RIC alloHCT from 2017-2021. The primary endpoint was the time to neutrophil engraftment. Secondary endpoints included length of stay (LOS) and the time to platelet engraftment as well as the incidence of infectious events, acute GVHD (aGVHD), and mucositis. RESULTS: Thirty-two patients were included in each group with similar baseline characteristics. We observed faster neutrophil engraftment (median 12 vs. 15 days, p = 0.01) and platelet engraftment (median 13 vs. 15 days, p = 0.026) with day + 4 vs. day + 12 G-CSF initiation. Median LOS was 23 days (range, 19-32) with day + 4 initiation vs. 24 days (21-30) with day + 12 (p = 0.046). The incidence of culture-negative febrile neutropenia (p = 0.12), any grade aGVHD (p = 0.58), and grade 2-4 mucositis (p = 0.8) were similar between groups. CONCLUSION: Compared to day + 4, day + 12 G-CSF initiation following RIC alloHCT had a longer time to neutrophil and platelet engraftment. Day + 12 initiation also resulted in longer LOS, which while statistically significant, was potentially of limited clinical significance. These findings are hypothesis generating.

Tacrolimus induced pseudogout following allogeneic hematopoietic cell transplant.

INTRODUCTION: Crystalline arthritis (CA), characterized by acute joint pain and erythema secondary to calcium pyrophosphate deposition (CPPD, or pseudogout) or monosodium urate crystals (gout), is a potentially underreported complication following allogeneic hematopoietic cell transplant (alloHCT). Graft-versus-host disease prophylaxis with calcineurin inhibitors (CNIs) causes hypomagnesemia and hyperuricemia, resulting in CA. CA related to tacrolimus has yet to be characterized following alloHCT. CASE REPORT: We retrospectively reviewed records of 450 consecutive patients undergoing alloHCT and identified 15 (3.3% incidence) who developed CA on tacrolimus. Large joints were involved in 10 (66.7%) patients, all patients had recent hypomagnesemia, and no patient had hyperuricemia, suggesting CPPD was the most likely etiology.Management and outcome: Eleven (73.3%) patients received systemic corticosteroids; 6 as initial therapy and 5 added to or substituted for colchicine in the setting of slow or inadequate response. The median duration of corticosteroid therapy was 6 days, however 2 patients (13.3%) required prolonged maintenance due to recurrence. Eleven (73.3%) patients received colchicine; 9 as initial therapy and 2 added to or substituted for corticosteroids in the setting of slow or inadequate response. The median duration of colchicine therapy was 18 days. The median time to symptom resolution was 21 days. DISCUSSION: Patients on tacrolimus following alloHCT presenting with acute joint pain and erythema should be evaluated for CPPD. Hypomagnesemia secondary to CNIs is likely the precipitating factor for CPPD in this population. Patients can effectively be managed with systemic corticosteroids and/or colchicine, however prolonged duration of treatment and even maintenance may be necessary. Based on the Naranjo Algorithm, CPPD secondary to tacrolimus induced hypomagnesemia is a possible adverse drug event, with a score of 3-4.

Risk of invasive fungal infections in patients with high-risk MDS and AML receiving hypomethylating agents.

Invasive fungal infections (IFI) are a significant source of morbidity and mortality for patients with acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS). Given the heterogeneity of the population receiving hypomethylating agents (HMA), it is difficult for clinicians to accurately assess their patients' risk of infection. Literature on the incidence of IFI following HMA is limited to several studies of azacitidine. The primary objective of this retrospective study was to establish the incidence of IFI in HMA treated AML/MDS patients at a large U.S. comprehensive cancer center. Secondary objectives included comparing incidence of IFI among pre-specified subgroups to identify potential risk factors for IFI. Two hundred three patients with AML, intermediate to very high risk MDS or chronic myelomonocytic leukemia who received at least two cycles of HMA were included. The incidence of IFI, as defined by the European Organization for Research and Treatment of Cancer / Invasive Fungal Infections Cooperative Group criteria, was 9.6%, with 20 IFI diagnosed following HMA (three proven, four probable, 13 possible). Among the proven cases of IFI, molds included Scedosporium and Fusarium spp. Eleven patients who developed IFIs were neutropenic upon initiating HMA. The majority (17/20) of infections occurred during the first four cycles. Given this incidence, mold-active prophylaxis can be considered in patients who are neutropenic at the start of therapy.

Oral Vancomycin Prophylaxis Is Highly Effective in Preventing Clostridium difficile Infection in Allogeneic Hematopoietic Cell Transplant Recipients.

BACKGROUND: Clostridium difficile infection (CDI) is a leading cause of infectious complications in allogeneic hematopoietic cell transplant recipients (alloHCT). We sought to evaluate whether prophylactic oral vancomycin reduces the incidence of CDI in alloHCT recipients. METHODS: We conducted a retrospective cohort study to examine the effectiveness of CDI prophylaxis with oral vancomycin, as compared to no prophylaxis, in 145 consecutive adult alloHCT recipients at the University of Pennsylvania between April 2015 and November 2016. Patients received oral vancomycin 125 mg twice daily, starting on admission and continuing until discharge. The primary outcome of interest was the association between oral vancomycin prophylaxis and CDI diagnosis. Secondary outcomes included graft-versus-host disease (GVHD) and relapse. RESULTS: There were no cases of CDI in patients that received prophylaxis (0/90, 0%), whereas 11/55 (20%) patients who did not receive prophylaxis developed CDI (P < .001). Oral vancomycin prophylaxis was not associated with a higher risk of acute, grades 2-4 GVHD (subhazard ratio [sHR] 1.59; 95% confidence interval [CI] 0.88-2.89; P = .12), acute, grades 3-4 GVHD (sHR 0.65; 95% CI 0.25-1.66; P = .36), or acute, grades 2-4 gastrointestinal GVHD (sHR 1.95; 95% CI 0.93-4.07; P = .08) at day 180 post-transplant. No associations between oral vancomycin and relapse or survival were observed. CONCLUSIONS: Prophylaxis with oral vancomycin is highly effective in preventing CDI in alloHCT recipients without increasing the risk of graft-versus-host disease or disease relapse. Further evaluation via a prospective study is warranted.

Cytokine Release Syndrome with Chimeric Antigen Receptor T Cell Therapy.

Chimeric antigen receptor (CAR)-modified T cells (CAR-Ts) targeting CD19 have resulted in unprecedented durable remissions for patients with relapsed and refractory B cell malignancies. Cytokine release syndrome (CRS), resulting from rapid immune activation induced by CAR-Ts, is the most significant treatment-related toxicity. CRS initially manifests with fever and can progress to life-threatening capillary leak with hypoxia and hypotension. The clinical signs of CRS correlate with T cell activation and high levels of cytokines including IL-6. Tocilizumab, an anti-IL-6 receptor antagonist, is the standard for CRS management, but optimal timing of administration is unclear. The development of a supportive infrastructure by treatment centers is important to maintain safe administration as access expands. Collaborative efforts are underway to harmonize the definition and grading of CRS to allow for better interpretation of toxicities across CAR-T products and clinical trials and allow for informed management algorithms.

Extended CCR5 Blockade for Graft-versus-Host Disease Prophylaxis Improves Outcomes of Reduced-Intensity Unrelated Donor Hematopoietic Cell Transplantation: A Phase II Clinical Trial.

Graft-versus-host disease (GVHD) remains the most common treatment-related complication after allogeneic hematopoietic cell transplantation (allo-HCT). Lymphocyte migration plays a critical role in the pathogenesis of GVHD. A previous phase I/II trial demonstrated that CCR5 blockade with maraviroc in the first 30days after allo-HCT resulted in a low incidence of early acute GVHD, primarily in visceral organs, but with no impact on late acute or chronic GVHD. We conducted a phase II trial to examine the efficacy of an extended course of maraviroc, administered through post-transplantation day +90 in addition to standard prophylaxis in 37 recipients of reduced-intensity-conditioned unrelated donor allo-HCT performed to treat hematologic malignancies. Extended maraviroc treatment was safe and feasible. The primary study endpoint, day +180 rate of grade II-IV acute GVHD, was 22 ± 7%, liver GVHD was not observed, and gut GVHD was uncommon. The day +180 rate of grade III-IV acute GVHD was 5 ± 4%. The 1-year rate of moderate to severe chronic GVHD was 8 ± 5% and that of disease relapse was 30 ± 8%. Overall survival at 1 year was 70 ± 8%. Compared with the previously studied short course of maraviroc, the extended course resulted in a significantly higher GVHD-free, relapse-free survival (adjusted hazard ratio [HR], .45; 95% confidence interval [CI], .25 to .82; P = .009) and overall survival (adjusted HR, .48; 95% CI, .24 to .96; P = .037). A combined analysis of both trials showed that high maraviroc trough concentrations on the day of hematopoietic cell infusion were associated with lower rates of acute GVHD. An extended course of maraviroc after reduced-intensity-conditioned unrelated donor allo-HCT is safe and effective in preventing acute and chronic GVHD and is associated with favorable survival.

ASTCT Consensus Grading for Cytokine Release Syndrome and Neurologic Toxicity Associated with Immune Effector Cells.

Chimeric antigen receptor (CAR) T cell therapy is rapidly emerging as one of the most promising therapies for hematologic malignancies. Two CAR T products were recently approved in the United States and Europe for the treatment ofpatients up to age 25years with relapsed or refractory B cell acute lymphoblastic leukemia and/or adults with large B cell lymphoma. Many more CAR T products, as well as other immunotherapies, including various immune cell- and bi-specific antibody-based approaches that function by activation of immune effector cells, are in clinical development for both hematologic and solid tumor malignancies. These therapies are associated with unique toxicities of cytokine release syndrome (CRS) and neurologic toxicity. The assessment and grading of these toxicities vary considerably across clinical trials and across institutions, making it difficult to compare the safety of different products and hindering the ability to develop optimal strategies for management of these toxicities. Moreover, some aspects of these grading systems can be challenging to implement across centers. Therefore, in an effort to harmonize the definitions and grading systems for CRS and neurotoxicity, experts from all aspects of the field met on June 20 and 21, 2018, at a meeting supported by the American Society for Transplantation and Cellular Therapy (ASTCT; formerly American Society for Blood and Marrow Transplantation, ASBMT) in Arlington, VA. Here we report the consensus recommendations of that group and propose new definitions and grading for CRS and neurotoxicity that are objective, easy to apply, and ultimately more accurately categorize the severity of these toxicities. The goal is to provide a uniform consensus grading system for CRS and neurotoxicity associated with immune effector cell therapies, for use across clinical trials and in the postapproval clinical setting.

Clinical Utilization of Chimeric Antigen Receptor T Cells in B Cell Acute Lymphoblastic Leukemia: An Expert Opinion from the European Society for Blood and Marrow Transplantation and the American Society for Blood and Marrow Transplantation.

On August 30, 2017 the US Food and Drug Administration approved tisagenlecleucel (Kymriah; Novartis, Basel, Switzerland), a synthetic bioimmune product of anti-CD19 chimeric antigen receptor T cells (CAR-T), for the treatment of children and young adults with relapsed/refractory B cell acute lymphoblastic leukemia (B-ALL). With this new era of personalized cancer immunotherapy, multiple challenges are present, ranging from implementation of a CAR-T program to safe delivery of the drug, long-term toxicity monitoring, and disease assessments. To address these issues experts representing the American Society for Blood and Marrow Transplant, the European Society for Blood and Marrow Transplantation, the International Society of Cell and Gene Therapy, and the Foundation for the Accreditation of Cellular Therapy formed a global CAR-T task force to identify and address key questions pertinent for hematologists and transplant physicians regarding the clinical use of anti CD19 CAR-T therapy in patients with B-ALL. This article presents an initial roadmap for navigating common clinical practice scenarios that will become more prevalent now that the first commercially available CAR-T product for B-ALL has been approved.

Cellular kinetics of CTL019 in relapsed/refractory B-cell acute lymphoblastic leukemia and chronic lymphocytic leukemia.

Tisagenlecleucel (CTL019) is an investigational immunotherapy that involves reprogramming a patient's own T cells with a transgene encoding a chimeric antigen receptor to identify and eliminate CD19-expressing cells. We previously reported that CTL019 achieved impressive clinical efficacy in patients with relapsed/refractory B-cell acute lymphoblastic leukemia (ALL) and chronic lymphocytic leukemia (CLL), including the expansion and persistence of CTL019 cells, which correlates with response to therapy. Here, we performed formal cellular kinetic analyses of CTL019 in a larger cohort of 103 patients treated with CTL019 in 2 different diseases (ALL and CLL). CTL019 was measured in peripheral blood and bone marrow, using quantitative polymerase chain reaction and flow cytometry. CTL019 levels in peripheral blood typically peaked at 10 to 14 days postinfusion and then declined slowly over time. Patients with complete response (CR)/CR with incomplete count recovery had higher levels of CTL019 in peripheral blood, with greater maximal concentration and area under the curve values compared with nonresponding patients (P < .0001 for each). CTL019 transgene levels were measurable up to 780 days in peripheral blood. CTL019 trafficking and persistence were observed in bone marrow and cerebrospinal fluid. CTL019 expansion correlated with severity of cytokine release syndrome (CRS) and preinfusion tumor burden in pediatric ALL. The results described here are the first detailed formal presentation of cellular kinetics across 2 diseases and highlight the importance of the application of in vivo cellular kinetic analyses to characterize clinical efficacy and CRS severity associated with CTL019 therapy.

Chimeric antigen receptor T cells for acute lymphoblastic leukemia.

Chimeric antigen receptor (CAR) modified T cells targeted to CD19 have resulted in unprecedented remission rates for adult and pediatric patients with relapsed and refractory B cell acute lymphoblastic leukemia (ALL). With regulatory approval for tisagenlecleucel and many other agents under active investigation, the use of CAR T cells for ALL continues to expand. While some remissions from anti-CD19 CAR T cells are durable without a consolidative allogeneic stem cell transplantation, CD19 positive and negative relapses remain a significant concern fueling investigations into the biology of CAR T cell persistence and the development of CARTs that target more than 1 antigen. The treatment related toxicities of cytokine release syndrome and neurologic events are potentially life threatening but recent advances have improved understanding and management strategies. This review summarizes outcomes for patients with ALL treated with CD19-CAR T cells while exploring the field's challenges and future directions.

Higher Donor Apheresis Blood Volumes Are Associated with Reduced Relapse Risk and Improved Survival in Reduced-Intensity Allogeneic Transplantations with Unrelated Donors.

Allogeneic hematopoietic stem cell transplantation (HSCT) with reduced-intensity conditioning (RIC) offers a curative option for patients with hematologic malignancies who are unable to undergo myeloablative conditioning, but its success is limited by high rates of relapse. Several studies have suggested a role for T cell doses in peripheral blood stem cell grafts in RIC HSCT. Because T cell dose is typically not known until after the collection, and apheresis blood volume is easily modifiable, we hypothesized that higher donor apheresis blood volumes would improve transplantation outcomes through an effect on graft composition. Thus, we analyzed the relationships between apheresis volume, graft composition, and transplantation outcomes in 142 consecutive patients undergoing unrelated donor allogeneic RIC HSCT. We found that apheresis volume ≥15 L was associated with a significantly decreased risk of relapse (adjusted hazard ratio [aHR], .48; 95% confidence interval [CI], .28 to .84]; P = .01) and improved relapse-free survival (aHR, .56; 95% CI, .35 to .89; P = .02) and overall survival (aHR, .55; 95% CI, .34 to .91; P = .02). A high apheresis volume was not associated with increased rates of acute or chronic graft-versus-host disease. These results demonstrate that an apheresis volume of at least 15 L is independently predictive of improved transplantation outcomes after RIC allogeneic HSCT.