Outcomes of hematopoietic cell transplantation in adult patients with acquired aplastic anemia using intermediate-dose alemtuzumab-based conditioning

Similar outcomes of alemtuzumab-based hematopoietic cell transplantation for SAA patients older or younger than 50 years

Survival after allogeneic hematopoietic cell transplantation (HSCT) for severe aplastic anemia (SAA) among older patients remains poor and associated with increased risk for graft-versus-host disease (GVHD). In this retrospective study of 65 consecutive patients with acquired SAA who were transplanted using fludarabine, low-dose cyclophosphamide, and alemtuzumab (FCC), outcomes of 27 patients aged at least 50 years were compared with those of 38 patients younger than 50 years. The median age of the older cohort was 61 years (range, 51-71 years); 21 (78%) patients were transplanted from unrelated donors (3 of 21 from HLA 9/10 mismatch donors) and 6 from matched sibling donors. One-year GVHD-free, relapse-free survival (GRFS) was comparable to that of patients younger than 50 years (84% vs 94%, respectively; P = .23). Both groups showed low rates of acute (5% vs 4%) and chronic (18% vs 14%) GVHD, with no cases of severe GVHD among matched donor transplants, and similar 1-year transplant-related mortality (14% vs 5.4%, older vs younger; P = .23). HSCT comorbidity index (HTC-CI) scores were similar between the groups, but overall survival with an HCT-CI of at least 3 was lower compared with a score less than 3 (76% vs 98%; P = .005). Median donor T-cell chimerism among older patients was 64% and 60% at 1 and 3 years, respectively, and was similar to that of younger patients. Increased B regulatory cells potentially contributed to low alloreactivity and mutual donor-recipient tolerance in older patients. Effect of comorbidities rather than age alone may be a more important determinant of suitability for FCC HSCT in older patients.

The Case for Upfront HLA-Matched Unrelated Donor Hematopoietic Stem Cell Transplantation as a Curative Option for Adult Acquired Severe Aplastic Anemia

The improved success of HLA-matched unrelated donor (MUD) hematopoietic stem cell transplantation (HSCT) for severe aplastic anemia (SAA) in recent decades has had an impact on the indications for and timing of this treatment modality. In the absence of a matched sibling donor (MSD), historically MUD HSCT was reserved as an option after failure to respond to at least 2 courses of immunosuppressive therapy (IST) in adults with SAA, but with improved outcomes over time, it is now considered following failure to respond to 1 course of IST. Recent national and international studies and guidelines now recommend upfront MUD HSCT as an option for children for whom an MUD is readily available, because outcomes are similar to those for MSD HSCT. Fludarabine-based conditioning and the use of in vivo T cell depletion with antithymocyte globulin or alemtuzumab has been associated with a reported overall survival (OS) of >85% in adult patients undergoing MUD HSCT. However, the recent introduction of eltrombopag for patients with SAA has transformed the treatment landscape, and there is currently much interest in its use with IST as upfront treatment, which showed a high response rate in an early-phase study. The risks of HSCT, especially graft-versus-host disease (GVHD), need to be carefully balanced against the concerns of IST, namely relapse and later clonal evolution to myelodysplastic syndrome (MDS)/acute myelogenous leukemia (AML). In the absence of a current prospective randomized trial comparing these 2 approaches, in this review we examine the evidence supporting consideration of early MUD HSCT in adults with SAA who would have been considered for MSD HSCT but who lack a MSD and for whom an MUD is readily available, especially using an irradiation-free conditioning regimen, with a low risk of GVHD, as another treatment option. This option may be offered to patients to provide them with an informed choice, with the aim of curing disease rather than achieving freedom from disease, relapse-free survival, or OS. Furthermore, understanding the immune signature for the response to IST and the immunologic responses to somatic mutations and clonal progression to MDS/AML may help define the future indications for upfront HSCT and a more precise medical approach to therapy.

Principles of alemtuzumab immunoablation in hematopoietic cell transplantation for non-malignant diseases in children: A review

Alemtuzumab is a humanized mAb targeted to CD52. Alemtuzumab is highly immunosuppressive with the ability to deplete T and B cells (in addition to other immune cell lines). A growing understanding of the PKs, dosing, and timing of administration of alemtuzumab has allowed for the study of its use as a conditioning agent for allogeneic HCT. The highly immunosuppressive properties of the drug are particularly appealing in the setting of non-malignant HCT, where GVHD provides no clinical benefit and relapse of malignancy is not applicable. In addition, the degree of immune suppression achieved with alemtuzumab has allowed for a reduction in the intensity of myeloablative cytotoxic agents included in some HCT conditioning regimens, allowing for fewer acute and late toxicities. This review paper will provide a comprehensive summary of the mechanism of action, PKs, dosing, and timing of alemtuzumab, a brief description of its use in various allogeneic HCT protocols for non-malignant conditions and a summary of the data regarding its use for GVHD therapy. The goal of this review was to provide an understanding as to how alemtuzumab might be safely incorporated into HCT conditioning regimens for children with non-malignant disease, allowing for expanded access to curative HCT therapy.

Fludarabine-based reduced intensity regimen for matched related donor hematopoietic stem cell transplantation in acquired severe aplastic anemia

Different conditioning regimens have been evaluated in matched-related donor allogeneic hematopoietic stem cell transplantation (allo-HSCT) for acquired severe aplastic anemia (SAA) with varying results. In this manuscript, we report our experience with fludarabine (120mg/m²), very low dose cyclophosphamide (1200mg/m²) and antithymocyte globulin (7.5mg/kg). Low dose total body irradiation (2Gy) was added to the conditioning regimen for patients older than 15 years. Nineteen patients (median age 23years) underwent transplant between 2008 and 2015. The majority (89%) were younger than 40 years. Stem cell source was BM (n=11) or PBSC (n=8). GvHD prophylaxis consisted of cyclosporine and either a short course of methotrexate (n=9) or mycophenolate mofetil (n=10). Eighteen (94.7%) patients achieved sustained engraftment. The median times to neutrophil and platelet engraftments were 19 (range: 14-34) and 17.1 (range: 12-25) days, respectively. The day-30 cumulative incidence of neutrophil and platelet engraftment was 89.4% and 94.7%, respectively. No secondary graft rejection was observed. The 1-year cumulative incidence of aGvHD (grade II-IV) and cGvHD was 11.7% and 0%, respectively. The 2-year GvHD-free survival rate was 78.6% (95% CI: 52.5-91.4%). Fludarabine-based reduced intensity regimen for MRD allo-HSCT in SAA compares favorably to other available regimens. This regimen deserves further investigations with larger cohort of patients.

Urologic Outcomes of Children With Hemorrhagic Cystitis After Bone Marrow Transplant at a Single Institution

OBJECTIVE

To analyze clinical outcomes and the risk factors associated with genitourinary (GU) morbidity and mortality in children who present with hemorrhagic cystitis (HC) after bone marrow transplant (BMT).

METHODS

A retrospective chart review of patients with HC who had undergone BMT at a single pediatric hospital from 2008 to 2015 was conducted. Demographic data, severity of hematuria, HC management, and mortality were analyzed. Bivariate analysis and binary logistic regression were performed to identify risk factors.

RESULTS

Out of 43 patients who met inclusion criteria, 67.4% were male with a median age at BMT of 10.2 years (interquartile range 5.8-14.6). Percutaneous nephrostomy catheters were inserted in 5 patients for urinary diversion. All-cause mortality was 32.6% (N = 14). Intravesical retroviral therapy (P <.001), HC grade (P <.001), total Foley time (P <.001), total gross hematuria time (P <.001), total days hospitalized (P = .012), and days to most improved hematuria (P = .032) were associated with significant GU morbidity on bivariate analysis. On multivariable analysis, days to most improved hematuria was associated with significant GU morbidity odds ratio of 1.177 (1.006-1.376) (P = .042). Status of percutaneous nephrostomy was not associated with increased mortality (P = .472); however, in the multivariate model, BK viremia (P = .023), need for renal dialysis (P = .003), and presence of Foley catheter (P = .005) were associated with increased mortality.

CONCLUSION

Children with HC after BMT fall in a very high-risk category with high mortality and significant GU morbidity. The presence of a Foley catheter, need for dialysis, and BK viremia are associated with increased mortality.

Evolving hematopoietic stem cell transplantation strategies in severe aplastic anemia

PURPOSE OF REVIEW

Significant improvements in unrelated donor hematopoietic stem cell transplantation (HSCT) in recent years have solidified its therapeutic role in severe aplastic anemia (SAA) and led to the evolution of treatment algorithms, particularly for children.

RECENT FINDINGS

Advances in understanding the genetics of inherited bone marrow failure syndromes (IBMFS) have allowed more confidence in accurately diagnosing SAA and avoiding treatments that could be dangerous and ineffective in individuals with IBMFS, which can be diagnosed in 10-20% of children presenting with a picture of SAA. Additionally long-term survival after matched sibling donor and matched unrelated donor HSCT now exceed 90% in children. Late effects after HSCT for SAA are minimal with current strategies, and compare favorably to late effects after upfront immunosuppressive therapy, except for patients with chronic graft versus host disease.

SUMMARY

Careful assessment for signs or symptoms of IBMFS, along with genetic screening for these disorders, is of major importance. Matched sibling donor HSCT is already considered the standard of care for upfront therapy and some groups are evaluating matched unrelated donor HSCT as primary therapy. Ongoing studies will continue to challenge treatment algorithms and may lead to an even more expanded role for HSCT in SAA.