We report results of a retrospective analysis of 44 patients with relapsed and high-risk multiple myeloma (MM) undergoing allogeneic CD34-selected hematopoietic stem cell transplantation (HSCT) from HLA-compatible donors. Patients had multiply relapsed disease including relapse at <15 months after autologous transplantation and most patients (28 of 44; 65%) also had high-risk cytogenetics. Before transplantation, patients received busulfan (.8 mg/kg × 10 doses), melphalan (70 mg/m(2) × 2 days), fludarabine (25 mg/m(2) × 5 days), and rabbit antithymocyte globulin (2.5 mg/kg × 2 days). Patients with 10/10 HLA- matched donors were treated prophylactically with low doses of donor lymphocyte infusions (.5 to 1 × 10(6) CD3(+)/kg) starting 4 to 6 months after CD34-selected HSCT. Acute (grade II to IV) graft-versus-host disease (GVHD) and transplantation-related mortality at 12 months were 2% and 18%, respectively. Chronic GVHD was not observed in any patient. Overall and progression-free survival at 2 years were 54% and 31%, respectively. By multivariate analyses, the outcomes of CD34-selected HSCT were influenced by presence of extramedullary disease, disease status before CD34-selected HSCT, and age. This study demonstrates notable safety and efficacy of CD34-selected HSCT in patients with multiply relapsed MM, including those with high-risk cytogenetics.

A common method to prevent graft-versus-host disease after allogeneic hematopoietic cell transplantation (HCT) from an HLA-mismatched unrelated donor (MMUD) is tacrolimus, methotrexate, and antithymocyte globulin (ATG). The use of posttransplant cyclophosphamide (PTCy) showed promise in a prospective trial for MMUD HCT. We compared 1-year graft-versus-host disease-free, relapse-free survival (GRFS) in 128 recipients of prophylaxis based on tacrolimus/methotrexate/ATG (ATG group, n = 46) vs PTCy, mycophenolate mofetil, and tacrolimus or sirolimus (PTCy group, n = 82) after MMUD HCT. Patients receiving HCT from a MMUD mismatched at ≥1 locus among HLA-A, HLA-B, HLA-C, and HLA-DRB1 were included. The 2 groups were well matched for HCT indication, high-risk disease, and HCT comorbidity index, whereas more patients on PTCy received bone marrow (50% vs 26%; P = .01) and >1 locus HLA-mismatched (30.5% vs 2.2%; P = .001) grafts. The 1-year GRFS was 16% (95% confidence interval (CI): 8%-31%) vs 54% (95% CI: 44%-66%; P < .001) in the ATG and PTCy groups, respectively. The multivariable adjusted hazard ratio for GRFS was 0.34 (95% CI: 0.21-0.55; P < .001) with the use of PTCy. The 1-year overall survival in the ATG group was 45% (95% CI: 32%-62%) vs 75% (95% CI: 66%-85%) in the PTCy group (P < .001). Relapse incidence was similar. One-year nonrelapse mortality was greater after ATG-based prophylaxis: 38% (95% CI: 23%-52%) vs 16% (95 CI: 9%-25%), P < .001. In summary, PTCy-based prophylaxis resulted in superior GRFS and overall survival in recipients of MMUD.

Clonal hematopoiesis (CH), as evidenced by recurrent somatic mutations in leukemia-associated genes, commonly occurs among aging human hematopoietic stem cells. We analyzed deep-coverage, targeted, next-generation sequencing (NGS) data of paired tumor and blood samples from 8,810 individuals to assess the frequency and clinical relevance of CH in patients with non-hematologic malignancies. We identified CH in 25% of cancer patients, with 4.5% harboring presumptive leukemia driver mutations (CH-PD). CH was associated with increased age, prior radiation therapy, and tobacco use. PPM1D and TP53 mutations were associated with prior exposure to chemotherapy. CH and CH-PD led to an increased incidence of subsequent hematologic cancers, and CH-PD was associated with shorter patient survival. These data suggest that CH occurs in an age-dependent manner and that specific perturbations can enhance fitness of clonal hematopoietic stem cells, which can impact outcome through progression to hematologic malignancies and through cell-non-autonomous effects on solid tumor biology.

The American Society for Blood and Marrow Transplantation (ASBMT) Clinical Case Forum (CCF) was launched in 2014 as an online secure tool to enhance interaction and communication among hematopoietic cell transplantation (HCT) professionals worldwide through the discussion of challenging clinical care issues. After 14 months, we reviewed clinical and demographical data of cases posted in the CCF from January 29, 2014 to March 18, 2015. A total of 137 cases were posted during the study period. Ninety-two cases (67%) were allogeneic HCT, 29 (21%) were autologous HCT, and in 16 (12%), the type of transplantation (autologous versus allogeneic) was still under consideration. The diseases most frequently discussed included non-Hodgkin lymphoma (NHL; n = 30, 22%), acute myeloid leukemia (n = 23, 17%), and multiple myeloma (MM; n = 20, 15%). When compared with the US transplantation activity reported by the US Department of Health and Human Services, NHL and acute lymphoblastic leukemia cases were over-represented in the CCF, whereas MM was under-represented (P < .001). A total of 259 topics were addressed in the CCF with a median of 2 topics/case (range, 1 to 6). Particularly common topics included whether transplantation was indicated (n = 57, 41%), conditioning regimen choice (n = 44, 32%), and post-HCT complications after day 100 (n = 43, 31%). The ASBMT CCF is a successful tool for collaborative discussion of complex cases in the HCT community worldwide and may allow identification of areas of controversy or unmet need from clinical, educational and research perspectives.

In this study, we compared transplantation outcomes of allogeneic hematopoietic stem cell transplantation (HSCT) in patients with advanced myelodysplastic syndrome (MDS) who received a CD34+ cell-selected and those who received an unmodified allograft. This analysis initially included 181 patients, 60 who received a CD34+ cell-selected transplant and 121 who received an unmodified transplant. Owing to significant differences in disease characteristics, the analysis was limited to patients with <10% blasts before HSCT (n = 145). Two groups were defined: low risk, with low- and intermediate-risk cytogenetics (CD34+, n = 39; unmodified, n = 46), and high risk: poor and very poor risk cytogenetics (CD34+, n = 19; unmodified, n = 41). In the low-risk group, the incidence of grade II-IV acute graft-versus-host disease (aGVHD) at 1 year post-transplantation was 18% in the CD34+ subgroup versus 41.3% in the unmodified subgroup (P = .015). There were no differences between the subgroups in the incidence of grade III-IV aGVHD. The incidence of chronic graft-versus-host disease (cGVHD) at 3 years in the 2 subgroups was 5.3% and 56%, respectively (P < .001). At 3 years post-transplantation, relapse, overall survival (OS), and relapse-free survival (RFS) were similar in the CD34+ and unmodified subgroups: 8.1% versus 19.4% (P = .187), 58.5% versus 53.7% (P = .51), and 59.5% versus 52.4% (P = .448). However, the composite outcome combining extensive cGVHD-free status and relapse-free status (CRFS) at 3 years was 59.5% in the CD34+ group versus 19.2% in the unmodified group (P < .001). In the high-risk group, grade II-IV aGVHD at 1 year was 31.6% in the CD34+ subgroup versus 24.4% in the unmodified subgroup (P = .752). There were no differences between the subgroups in the incidence of grade III-IV aGVHD. The incidence of cGVHD at 3 years in the 2 subgroups was 0% versus 27.6% (P = .013). At 3 years post-transplantation, relapse, OS, RFS, and CRFS in the 2 subgroups were 31.6% versus 69.3% (P = .007), 35.5% versus 14.5% (P = .068), 31.6% versus 10.7% (P = .045), and 31.6% versus 6.1% (P = .001), respectively. Cytogenetic abnormalities at diagnosis and transplant type had significant univariate associations with RFS in the high-risk cohort. Only cytogenetics (P = .03) remained associated with this outcome in a multivariate model. OS was similar in the 2 transplant groups; however, CRFS was superior in the CD34+ cell-selected transplant group.

Acquired mutations are pervasive across normal tissues. However, understanding of the processes that drive transformation of certain clones to cancer is limited. Here we study this phenomenon in the context of clonal hematopoiesis (CH) and the development of therapy-related myeloid neoplasms (tMNs). We find that mutations are selected differentially based on exposures. Mutations in ASXL1 are enriched in current or former smokers, whereas cancer therapy with radiation, platinum and topoisomerase II inhibitors preferentially selects for mutations in DNA damage response genes (TP53, PPM1D, CHEK2). Sequential sampling provides definitive evidence that DNA damage response clones outcompete other clones when exposed to certain therapies. Among cases in which CH was previously detected, the CH mutation was present at tMN diagnosis. We identify the molecular characteristics of CH that increase risk of tMN. The increasing implementation of clinical sequencing at diagnosis provides an opportunity to identify patients at risk of tMN for prevention strategies.

Tumor protein p53 (TP53) is the most frequently mutated gene in cancer^1,2. In patients with myelodysplastic syndromes (MDS), TP53 mutations are associated with high-risk disease^3,4, rapid transformation to acute myeloid leukemia (AML)⁵, resistance to conventional therapies^6-8 and dismal outcomes⁹. Consistent with the tumor-suppressive role of TP53, patients harbor both mono- and biallelic mutations¹⁰. However, the biological and clinical implications of TP53 allelic state have not been fully investigated in MDS or any other cancer type. We analyzed 3,324 patients with MDS for TP53 mutations and allelic imbalances and delineated two subsets of patients with distinct phenotypes and outcomes. One-third of TP53-mutated patients had monoallelic mutations whereas two-thirds had multiple hits (multi-hit) consistent with biallelic targeting. Established associations with complex karyotype, few co-occurring mutations, high-risk presentation and poor outcomes were specific to multi-hit patients only. TP53 multi-hit state predicted risk of death and leukemic transformation independently of the Revised International Prognostic Scoring System (IPSS-R)¹¹. Surprisingly, monoallelic patients did not differ from TP53 wild-type patients in outcomes and response to therapy. This study shows that consideration of TP53 allelic state is critical for diagnostic and prognostic precision in MDS as well as in future correlative studies of treatment response.