Phase II Trial of nab-Sirolimus in Patients With Advanced Malignant Perivascular Epithelioid Cell Tumors (AMPECT): Long-Term Efficacy and Safety Update.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.nab-Sirolimus is approved in the United States for the treatment of metastatic or locally advanced malignant perivascular epithelioid cell tumor (PEComa) on the basis of the primary analysis results of the phase II Advanced Malignant Perivascular Epithelioid Cell Tumors (AMPECT) trial (ClinicalTrials.gov identifier: NCT02494570). Results from the primary analysis were previously published; however, the median duration of response (mDOR) had not been reached at that time. Here, 3 years after the primary analysis, we report final efficacy and safety data (data cutoff: April 29, 2022). At study completion, the confirmed overall response rate (by independent radiologist review using RECIST v1.1) was 38.7% (95% CI, 21.8 to 57.8), with an additional converted confirmed complete response (n = 2). Median progression-free survival remained the same at 10.6 months (95% CI, 5.5 to 41.2). The mDOR was reached at 39.7 months (95% CI, 6.5 to not reached [NR]), and the median overall survival at completion was 53.1 months (95% CI, 22.2 to NR). The most common treatment-related adverse events (TRAEs) were stomatitis (82.4%) and fatigue and rash (each 61.8%). No new or unexpected adverse events occurred, and no grade ≥4 TRAEs were reported. These results highlight the long-term clinical benefit of nab-sirolimus in patients with advanced malignant PEComa, with a DOR of >3 years.

Tabelecleucel for allogeneic haematopoietic stem-cell or solid organ transplant recipients with Epstein-Barr virus-positive post-transplant lymphoproliferative disease after failure of rituximab or rituximab and chemotherapy (ALLELE): a phase 3, multicentre, open-label trial.

BACKGROUND: Survival in Epstein-Barr virus (EBV)-positive post-transplant lymphoproliferative disease following haematopoietic stem-cell transplant (HSCT) or solid organ transplant (SOT) is poor after failure of initial therapy, indicating an urgent need for therapies for this ultra-rare disease. With recent EU marketing authorisation, tabelecleucel is the first off-the-shelf, allogeneic, EBV-specific T-cell immunotherapy to receive approval for treatment of relapsed or refractory EBV-positive post-transplant lymphoproliferative disease. We aimed to determine the clinical benefit of tabelecleucel in patients with relapsed or refractory EBV-positive post-transplant lymphoproliferative disease following HSCT or SOT. METHODS: In this global, multicentre, open-label, phase 3 trial, eligible patients (of any age) had biopsy-proven EBV-positive post-transplant lymphoproliferative disease, disease that was relapsed or refractory to rituximab after HSCT and rituximab with or without chemotherapy after SOT, and partially HLA-matched and appropriately HLA-restricted tabelecleucel available. Patients received tabelecleucel administered intravenously at 2 × 106 cells per kg on days 1, 8, and 15 in 35-day cycles and are assessed for up to 5 years for survival post-treatment initiation. The primary endpoint was objective response rate. All patients who received at least one dose of tabelecleucel were included in safety and efficacy analyses. This trial is registered with ClinicalTrials.gov, NCT03394365, and is ongoing. FINDINGS: From June 27, 2018, to Nov 5, 2021, 63 patients were enrolled, of whom 43 (24 [56%] male and 19 [44%] female) were included, 14 had prior HSCT, 29 had SOT. Seven (50%, 95% CI 23-77) of 14 participants in the HSCT group and 15 (52%, 33-71) of 29 participants in the SOT group had an objective response, with a median follow-up of 14·1 months (IQR 5·7-23·9) and 6·0 months (1·8-18·4), respectively. The most common grade 3 or 4 treatment-emergent adverse events were disease progression (in four [29%] of 14 in HSCT and eight [28%] of 29 in SOT) and decreased neutrophil count (in four [29%] of 14 in HSCT and four [14%] of 29 in SOT). Treatment-emergent serious adverse events were reported in 23 (53%) of 43 patients and fatal treatment-emergent adverse events in five (12%); no fatal treatment-emergent adverse event was treatment-related. There were no reports of tumour flare reaction, cytokine release syndrome, immune effector cell-associated neurotoxicity syndrome, transmission of infectious diseases, marrow rejection, or infusion reactions. No events of graft-versus-host disease or SOT rejection were reported as related to tabelecleucel. INTERPRETATION: Tabelecleucel provides clinical benefit in patients with relapsed or refractory EBV-positive post-transplant lymphoproliferative disease, for whom there are no other approved therapies, without evidence of safety concerns seen with other adoptive T-cell therapies. These data represent a potentially transformative and accessible treatment advance for patients with relapsed or refractory disease with few treatment options. FUNDING: Atara Biotherapeutics.

Immune Recovery Following Autologous Hematopoietic Stem Cell Transplantation in HIV-Related Lymphoma Patients on the BMT CTN 0803/AMC 071 Trial.

We report a first in-depth comparison of immune reconstitution in patients with HIV-related lymphoma following autologous hematopoietic cell transplant (AHCT) recipients (n=37, lymphoma, BEAM conditioning), HIV(-) AHCT recipients (n=30, myeloma, melphalan conditioning) at 56, 180, and 365 days post-AHCT, and 71 healthy control subjects. Principal component analysis showed that immune cell composition in HIV(+) and HIV(-) AHCT recipients clustered away from healthy controls and from each other at each time point, but approached healthy controls over time. Unsupervised feature importance score analysis identified activated T cells, cytotoxic memory and effector T cells [higher in HIV(+)], and naïve and memory T helper cells [lower HIV(+)] as a having a significant impact on differences between HIV(+) AHCT recipient and healthy control lymphocyte composition (p<0.0033). HIV(+) AHCT recipients also demonstrated lower median absolute numbers of activated B cells and lower NK cell sub-populations, compared to healthy controls (p<0.0033) and HIV(-) AHCT recipients (p<0.006). HIV(+) patient T cells showed robust IFNγ production in response to HIV and EBV recall antigens. Overall, HIV(+) AHCT recipients, but not HIV(-) AHCT recipients, exhibited reconstitution of pro-inflammatory immune profiling that was consistent with that seen in patients with chronic HIV infection treated with antiretroviral regimens. Our results further support the use of AHCT in HIV(+) individuals with relapsed/refractory lymphoma.

Allogeneic Hematopoietic Cell Transplant for HIV Patients with Hematologic Malignancies: The BMT CTN-0903/AMC-080 Trial.

We set out to assess feasibility and safety of allogeneic hematopoietic cell transplant in 17 persons with HIV in a phase II prospective multicenter trial. The primary endpoint was 100-day nonrelapse mortality (NRM). Patients had an 8/8 HLA-matched related or at least a 7/8 HLA-matched unrelated donor. Indications for transplant were acute leukemia, myelodysplasia, and lymphoma. Conditioning was myeloablative or reduced intensity. There was no NRM at 100 days. The cumulative incidence of grades II to IV acute graft-versus-host disease (GVHD) was 41%. At 1 year, overall survival was 59%; deaths were from relapsed/progressive disease (n = 5), acute GVHD (n = 1), adult respiratory distress syndrome (n = 1), and liver failure (n = 1). In patients who achieved complete chimerism, cell-associated HIV DNA and inducible infectious virus in the blood were not detectable. Blood and Marrow Transplant Clinical Trials Network 0903/AIDS Malignancy Consortium 080 was registered at www.clinicaltrials.gov (no. NCT01410344).

First-in-Human Phase I Study of the Activin A Inhibitor, STM 434, in Patients with Granulosa Cell Ovarian Cancer and Other Advanced Solid Tumors.

PURPOSE: STM 434 is a soluble receptor ligand trap targeting activin A, a protein in the TGFß family that plays important roles in growth, differentiation, and cancer cachexia. This study evaluated the safety, antitumor activity, and metabolic effects of STM 434 in a first-in-human, multicenter, phase I clinical trial (NCT02262455). PATIENTS AND METHODS: Patients with advanced solid tumors were enrolled in 8 dose cohorts ranging from 0.25 mg/kg every 4 weeks to 8 mg/kg every 2 weeks via a 3 + 3 dose-escalation design. The primary endpoint was maximum tolerated dose (MTD). Secondary endpoints included safety, pharmacokinetics, and response. As activin A is implicated in metabolism and muscle function, changes in key metabolic parameters, including lean body mass and 6-minute walk test, were serially measured. RESULTS: Thirty-two patients were treated on study. The most common treatment-related adverse events were fatigue (41%) and mucocutaneous bleeding complications including epistaxis (34%) and gingival bleeding (22%), likely related to off-target inhibition of bone morphogenetic protein 9 (BMP9). STM 434 treatment resulted in the expected follicle-stimulating hormone level decreases in most patients and in metabolic parameter changes, including an increase in total lean body mass and 6-minute walk test distance. No responses were observed in the 30 evaluable patients, but the stable disease rate in patients with granulosa cell ovarian cancer was 10 of 12 (80%). CONCLUSIONS: Although no direct antitumor efficacy was documented, potentially clinically meaningful dose-related metabolic effects, including treatment of cancer cachexia, were observed that support further exploration of activin A inhibitors that limit BMP9 blockade.See related commentary by Bonilla and Oza, p. 5432.

Higher Risks of Toxicity and Incomplete Recovery in 13- to 17-Year-Old Females after Marrow Donation: RDSafe Peds Results.

Although donation of bone marrow (BM) or peripheral blood stem cells (PBSCs) from children to family members undergoing allogeneic transplantation are well-established procedures, studies detailing levels of pain, symptoms, and long-term recovery are lacking. To address this lack, we prospectively enrolled 294 donors age <18 years at 25 pediatric transplantation centers in North America, assessing them predonation, peridonation, and at 1 month, 6 months, and 1 year postdonation. We noted that 71% of children reported pain and 59% reported other symptoms peridonation, with resolution to 14% and 12% at 1 month postdonation. Both older age (age 13 to 17 years versus younger) and female sex were associated with higher levels of pain peridonation, with the highest rates in older females (57% with grade 2-4 pain and 17% with grade 3-4 pain). Multivariate analyses showed a 4-fold increase in risk for older females compared with males age <13 years (P <.001). At 1 year, 11% of 13- to 17-year-old females reported grade 2-4 pain, compared with 3% of males age 13 to 17 years, 0% of females age <13 years, and 1% of males age <13 years (P = .01). Males and females age 13 to 17 years failed to return to predonation pain levels at 1 year 22% and 23% of the time, respectively, compared with 3% and 10% in males and females age <13 years (P = .002). Our data show that females age 13 to 17 years are at increased risk of grade 2-4 pain at 1 year and >20% of females and males age 13 to 17 years do not return to baseline pain levels by 1 year after BM donation. Studies aimed at decreasing symptoms and improving recovery in older children are warranted.

Autologous hematopoietic cell transplantation for HIV-related lymphoma: results of the BMT CTN 0803/AMC 071 trial.

Autologous hematopoietic cell transplant (AHCT) for HIV-infected patients is largely limited to centers with HIV-specific expertise. The Blood and Marrow Transplant Clinical Trials Network 0803/AIDS Malignancy Consortium 071 trial is a multicenter phase 2 study of AHCT for patients with HIV-related lymphoma (HRL). Eligible patients had chemotherapy-sensitive relapsed/persistent HRL, were >15 years of age, and had treatable HIV infection. Patients were prepared using carmustine, etoposide, cytarabine, and melphalan and received consistent management of peritransplant antiretroviral treatment. The primary endpoint was 1-year overall survival. Forty-three patients were enrolled; 40 underwent AHCT. Pretransplant HIV viral load was undetectable (<50 copies/mL) in 32 patients (80%); the median CD4 count was 249/µL (range, 39-797). At a median follow-up of 24.8 months, 1-year and 2-year overall survival probabilities were 87.3% (95% confidence interval [CI], 72.1-94.5) and 82% (95% CI, 65.9-91), respectively. The probability of 2-year progression-free survival was 79.8% (95% CI, 63.7-89.4). One-year transplant-related mortality was 5.2%. Median time to neutrophil and platelet recovery was 11 days and 18 days, respectively. Nine patients experienced a total of 13 unexpected grade 3-5 adverse events posttransplant (10 grade 3 and 3 grade 4 events). Twenty-two patients had at least 1 infectious episode posttransplant. At 1 year post-AHCT, median CD4(+) T-cell count was 280.3 (range, 28.8-1148.0); 82.6% had an undetectable HIV viral load. Trial patients were compared with 151 matched Center for International Bone Marrow Transplant Research controls. Outcomes between HIV-infected patients and controls were not statistically significantly different. HRL patients should be considered candidates for AHCT if they meet standard transplant criteria. The trial was registered at www.clinicaltrials.gov as #NCT01141712.

Results of a prospective multicentre myeloablative double-unit cord blood transplantation trial in adult patients with acute leukaemia and myelodysplasia.

Double-unit cord blood (CB) grafts may improve engraftment and relapse risk in adults with haematological malignancies. We performed a prospective high-dose myeloablative double-unit CB transplantation (CBT) trial in adults with high-risk acute leukaemia or myelodysplasia (MDS) between 2007 and 2011. The primary aim was to establish the 1-year overall survival in a multi-centre setting. Fifty-six patients (31 acute myeloid leukaemia, 19 acute lymphoblastic leukaemia, 4 other acute leukaemias, 2 myelodysplastic syndrome [MDS]) were transplanted at 10 centres. The median infused total nucleated cell doses were 2·62 (larger unit) and 2·02 (smaller unit) x 10(7) /kg. The cumulative incidence of day 100 neutrophil engraftment was 89% (95% confidence interval [CI]: 80-96). Day 180 grade II-IV acute graft-versus-host disease (GVHD) incidence was 64% (95%CI: 51-76) and 36% (95%CI: 24-49) of patients had chronic GVHD by 3-years. At 3-years post-transplant, the transplant-related mortality (TRM) was 39% (95%CI: 26-52), and the 3-year relapse incidence was 11% (95%CI: 4-21). With a median 37-month (range 23-71) follow-up of survivors, the 3-year disease-free survival was 50% (95%CI: 37-63). Double-unit CBT is a viable alternative therapy for high-risk acute leukaemia/ MDS in patients lacking a matched unrelated donor. This is especially important for minority patients. The relapse incidence was low but strategies to ameliorate TRM are needed.

Lower risk for serious adverse events and no increased risk for cancer after PBSC vs BM donation.

We compared serious early and late events experienced by 2726 bone marrow (BM) and 6768 peripheral blood stem cell (PBSC) donors who underwent collection of PBSC or BM between 2004 and 2009 as part of a prospective study through the National Marrow Donor Program. Standardized FDA definitions for serious adverse events (SAEs) were used, and all events were reviewed by an independent physician panel. BM donors had an increased risk for SAEs (2.38% for BM vs 0.56% for PBSC; odds ratio [OR], 4.13; P < .001), and women were twice as likely to experience an SAE (OR for men, 0.50; P = .005). Restricting the analysis to life-threatening, unexpected, or chronic/disabling events, BM donors maintained an increased risk for SAEs (0.99% for BM vs 0.31% for PBSC; OR, 3.20; P < .001). Notably, the incidence of cancer, autoimmune illness, and thrombosis after donation was similar in BM vs PBSC donors. In addition, cancer incidence in PBSC donors was less than that reported in the general population (Surveillance, Epidemiology, and End Results Program database). In conclusion, SAEs after donation are rare but more often occurred in BM donors and women. In addition, there was no evidence of increased risk for cancer, autoimmune illness, and stroke in donors receiving granulocyte colony-stimulating factor during this period of observation.

Acute toxicities of unrelated bone marrow versus peripheral blood stem cell donation: results of a prospective trial from the National Marrow Donor Program.

Although peripheral blood stem cells (PBSCs) have replaced bone marrow (BM) as the most common unrelated donor progenitor cell product collected, a direct comparison of concurrent PBSC versus BM donation experiences has not been performed. We report a prospective study of 2726 BM and 6768 PBSC donors who underwent collection from 2004 to 2009. Pain and toxicities were assessed at baseline, during G-CSF administration, on the day of collection, within 48 hours of donation, and weekly until full recovery. Peak levels of pain and toxicities did not differ between the 2 donation processes for most donors. Among obese donors, PBSC donors were at increased risk of grade 2 to 4 pain as well as grade 2 to 4 toxicities during the pericollection period. In contrast, BM donors were more likely to experience grade 2 to 4 toxicities at 1 week and pain at 1 week and 1 month after the procedure. BM donors experienced slower recovery, with 3% still not fully recovered at 24 weeks, whereas 100% of PBSC donors had recovered. Other factors associated with toxicity included obesity, increasing age, and female sex. In summary, this study provides extensive detail regarding individualized risk patterns of PBSC versus BM donation toxicity, suggesting donor profiles that can be targeted with interventions to minimize toxicity.

Obesity does not preclude safe and effective myeloablative hematopoietic cell transplantation (HCT) for acute myelogenous leukemia (AML) in adults.

The incidence of excessive adiposity is increasing worldwide, and is associated with numerous adverse health outcomes. We compared outcomes by body mass index (BMI) for adult patients with acute myelogenous leukemia (AML) who underwent autologous (auto, n = 373), related donor (RD, n = 2041), or unrelated donor (URD, n = 1801) allogeneic myeloablative hematopoietic cell transplantation (HCT) using bone marrow or peripheral blood stem cells reported to the Center for International Blood and Marrow Transplant Research (CIBMTR) from 1995 to 2004. Four weight groups by BMI (kg/m(2)) were defined: underweight <18 kg/m(2); normal 18-25 kg/m(2); overweight >25-30 kg/m(2); and obese >30 kg/m(2). Multivariable analysis referenced to the normal weight group showed an increased risk of death for underweight patients in the RD group (relative risk [RR], 1.92; 95% confidence interval [CI], 1.28-2.89; P = .002), but not in the URD group. There were no other differences in outcomes among the other weight groups within the other HCT groups. Overweight and obese patients enjoyed a modest decrease in relapse incidence, although this did not translate into a survival benefit. Small numbers of patients limit the ability to better characterize the adverse outcomes seen in the underweight RD but not the underweight URD allogeneic HCT patients. Obesity alone should not be considered a barrier to HCT.

Methodological and logistical considerations to study design and data collection in racial/ethnic minority populations evaluating outcome disparity in hematopoietic cell transplantation.

Outcome disparity associated with race or ethnicity in the United States has been observed in hematopoietic cell transplantation (HCT). The underlying reasons for such disparity are not known. In the United States, an optimal study of health care disparity by race or ethnicity involves consideration of both biologic and psychosocial determinants, which requires an adequately powered, prospective cohort study design. To better characterize the nature and quantify the magnitude of the many impediments relevant to conducting a successful prospective study involving racial or ethnic minorities in HCT, we conducted a feasibility study to help guide planning of a larger scale outcome and disparity study in HCT. The primary questions to be addressed in the study were: (1) can we establish a racially or ethnically diverse patient sample that will respond to a survey focused on sociodemographic, economic, health insurance, cultural, spiritual, and religious well-being, and social support information? (2) What is the retention rate in the study over time? (3) What is the quality of the data collected from the patients over time? The challenges we faced in conducting this multicenter feasibility study are summarized in this report. Despite the difficulty in conducting disparity studies in racial and ethnic minorities, such studies are essential to ensure that people of all ethnic and racial backgrounds have the best chance possible of benefiting from HCT.

Second autologous stem cell transplantation for relapsed lymphoma after a prior autologous transplant.

We determined treatment-related mortality, progression-free survival (PFS), and overall survival (OS) after a second autologous HCT (HCT2) for patients with lymphoma relapse after a prior HCT (HCT1). Outcomes for patients with either Hodgkin lymphoma (HL, n = 21) or non-Hodgkin lymphoma (NHL, n = 19) receiving HCT2 reported to the Center for International Blood and Marrow Transplant Research (CIBMTR) were analyzed. The median age at HCT2 was 38 years (range: 16-61) and 22 (58%) patients had a Karnofsky performance score <90. HCT2 was performed >1 year after HCT1 in 82%. The probability of treatment-related mortality at day 100 was 11% (95% confidence interval [CI], 3%-22%). The 1-, 3-, and 5-year probabilities of PFS were 50% (95% CI, 34%-66%), 36% (95% CI, 21%-52%), and 30% (95% CI, 16%-46%), respectively. Corresponding probabilities of survival were 65% (95% CI, 50%-79%), 36% (95% CI, 22%-52%), and 30% (95% CI, 17%-46%), respectively. At a median follow-up of 72 months (range: 12-124 months) after HCT2, 29 patients (73%) have died, 18 (62%) secondary to relapsed lymphoma. The outcomes of patients with HL and NHL were similar. In summary, this series represents the largest reported group of patients with relapsed lymphomas undergoing SCT2 following failed SCT1, and with long-term follow-up. Our series suggests that SCT2 is feasible in patients relapsing after prior HCT1, with a lower treatment-related mortality than that reported for allogeneic transplant in this setting. HCT2 should be considered for patients with relapsed HL or NHL after HCT1 without alternative allogeneic stem cell transplant options.

Effect of body mass index on mortality of patients with lymphoma undergoing autologous hematopoietic cell transplantation.

High-dose therapy with autologous hematopoietic cell transplantation (auto-HCT) is frequently used to improve outcomes in lymphoma. However, small studies suggest a survival disadvantage among obese patients. Using a retrospective cohort analysis, we studied the outcomes of 4681 patients undergoing auto-HCT for Hodgkin or non-Hodgkin lymphoma between 1990 and 2000 according to body mass index (BMI). Four groups categorized by BMI were compared by using Cox proportional hazards regression to adjust for other prognostic factors. A total of 1909 patients were categorized as normal weight (BMI 18-25 kg/m2), 121 as underweight (BMI<18 kg/m2), 1725 as overweight (BMI>25-30 kg/m2), and 926 as obese (BMI>30 kg/m2) at the time of HCT. Outcomes evaluated included overall survival, relapse, transplantation-related mortality (TRM), and lymphoma-free survival. TRM was similar among the normal, overweight, and obese groups; the underweight group had a higher risk of TRM (relative risk [RR], 2.46; 95% confidence interval [CI], 1.59-3.82; P<0.0001) compared with the normal-BMI group. No differences in relapse were noted. Overall mortality was higher in the underweight group (RR, 1.48; 95% CI, 1.17-1.88; P=.001) and lower in the overweight (RR, 0.87; 95% CI, 0.79-0.96; P=.004) and obese (RR, 0.76; 95% CI, 0.67-0.86; P<.0001) groups compared with the normal-BMI group. In light of our inability to find differences in survival among overweight, obese, and normal-weight patients, obesity alone should not be viewed as a contraindication to proceeding with auto-HCT for lymphoma when it is otherwise indicated.

AIDS-related lymphoproliferative disease.

Not long after the recognition of HIV as the causative agent of AIDS, it was evident that individuals infected with HIV developed lymphoma at a greater rate than the population at large. Approximately two thirds of AIDS-related lymphoma (ARL) cases are categorized as diffuse large B-cell type, with Burkitt lymphomas comprising 25% and other histologies a much smaller proportion. Typically, these individuals have presented with advanced extranodal disease and CD4+ lymphocyte counts of less than 200/mm3. Recent clinical trials have demonstrated a better outcome with chemotherapy for ARL since the introduction of combination antiretroviral treatment, termed highly active antiretroviral therapy (HAART). For patients with relapses, solid evidence points to the safety and utility of hematopoietic-cell transplantation as a salvage modality. Coinfection with other viruses such as Epstein-Barr virus and Kaposi sarcoma-associated herpesvirus have led to the genesis of previously rare or unrecognized lymphoma subtypes such as plasmablastic and primary effusion lymphomas. The immunosuppressive impact of treatment for patients with ARL receiving chemotherapy with HAART appears transient and opportunistic infections have become less problematic than prior to HAART. Significant progress has been made in the understanding and management of ARL but outcomes still remain inferior compared to those achieved in HIV- individuals.

Differences in characteristics of US hematopoietic stem cell transplantation centers by proportion of racial or ethnic minorities.

Racial or ethnic minorities with leukemia who receive HLA-identical sibling hematopoietic stem cell transplants (HSCTs) are reported to have worse survival when compared with whites. Characteristics of US HSCT centers according to the proportion of ethnic minorities who undergo transplantation were compared to explore systematic differences among centers; the association with 100-day mortality was evaluated to determine whether center factors may explain the observed discrepant survival among ethnic minorities. One hundred sixteen US transplantation centers that performed HLA-identical sibling transplantations for leukemia were analyzed. We compared physician and health care provider staffing, transplantation unit procedure and resources, and medical center organization according to the volume procedure ratio of ethnic minorities who underwent transplantation and also according to the ratio of Hispanics who underwent transplantation. Centers that performed transplantation in a higher proportion of ethnic minorities were more likely to perform fewer transplantations per year, to have fewer devoted transplant beds, to be in an urban setting, to have a lower physician to patient volume ratio, and to follow up survivors 1 year after transplantation. Centers that performed transplantation in a higher proportion of Hispanics were more likely to perform fewer transplantations per year and to have fewer devoted transplantation beds, were less likely to perform outpatient transplantations, were more likely to be in an urban setting, and were less likely to have posttransplantation immunization protocols. Observed differences in center factors were not associated with 100-day mortality after adjustment for disease severity. Our results suggest that the inferior survival reported in ethnic minorities after HSCT may not be readily explained by center effects.