Malignant progression of donor-engrafted clonal hematopoiesis in sibling recipients after stem cell transplantation

Donor-Derived Malignancy and Transplantation Morbidity: Risks of Patient and Donor Genetics in Allogeneic Hematopoietic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a key treatment option for hematologic malignancies (HMs), although it carries significant risks. Up to 30% of patients relapse after allo-HSCT, of which up to 2% to 5% are donor-derived malignancies (DDMs). DDMs can arise from a germline genetic predisposition allele or clonal hematopoiesis (CH) in the donor. Increasingly, genetic testing reveals that patient and donor genetic factors contribute to the development of DDM and other allo-HSCT complications. Deleterious germline variants in CEBPA, DDX41, GATA2, and RUNX1 predispose to inferior allo-HSCT outcomes. DDM has been linked to donor-acquired somatic CH variants in DNMT3A, ASXL1, JAK2, and IDH2, often with additional new variants. We do not yet have evidence to standardize donor genetic sequencing prior to allo-HSCT. The presence of hereditary HM disorders should be considered in patients with myeloid malignancies and their related donors, and screening of unrelated donors should include family and personal history of cytopenia and HMs. Excellent multidisciplinary care is critical to ensure efficient timelines for screening and necessary discussions among medical oncologists, genetic counselors, recipients, and potential donors. After allo-HSCT, HM relapse monitoring with genetic testing effectively results in genetic sequencing of the donor, as the transplanted hematopoietic system is donor-derived, which presents ethical challenges for disclosure to patients and donors. We encourage consideration of the recent National Marrow Donor Program policy that allows donors to opt-in for notification about detection of their genetic variants after allo-HSCT, with appropriate genetic counseling when feasible. We look forward to prospective investigation of the impact of germline and acquired somatic genetic variants on hematopoietic stem cell mobilization/engraftment, graft-versus-host disease, and DDM to facilitate improved outcomes through knowledge of genetic risk.

Case report: Rare case of donor cell-derived T-cell acute lymphoblastic leukaemia in a female patient after receiving an allo-transplant from her male sibling

Donor-derived haematological neoplasms, in which recipients present with haematological malignancies that have evolved from transplant donor stem cells, have previously been described for myelodysplastic syndrome, myeloproliferative neoplasms, acute myeloid leukaemia and less often, leukaemias of lymphoid origin. Here we describe a rare and complex case of donor-derived T-cell acute lymphoblastic leukaemia with a relatively short disease latency of less than 4 years. Through genomic and in vitro analyses, we identified novel mutations in NOTCH1 as well as a novel activating mutation in STAT5B; the latter targetable with the clinically available drugs, venetoclax and ruxolitinib.

Clonal Hematopoiesis: Role in Hematologic and Non-Hematologic Malignancies

Hematopoietic stem cells (HSCs) ensure the coordinated and balanced production of all hematopoietic cell types throughout life. Aging is associated with a gradual decline of the self-renewal and regenerative potential of HSCs and with the development of clonal hematopoiesis. Clonal hematopoiesis of indeterminate potential (CHIP) defines the clonal expansion of genetically variant hematopoietic cells bearing one or more gene mutations and/or structural variants (such as copy number alterations). CHIP increases exponentially with age and is associated with cancers, including hematologic neoplasia, cardiovascular and other diseases. The presence of CHIP consistently increases the risk of hematologic malignancy, particularly in individuals who have CHIP in association with peripheral blood cytopenia.

Donor Clonal Hematopoiesis and Recipient Outcomes After Transplantation

PURPOSE

Clonal hematopoiesis (CH) can be transmitted from a donor to a recipient during allogeneic hematopoietic cell transplantation. Exclusion of candidate donors with CH is controversial since its impact on recipient outcomes and graft alloimmune function is uncertain.

PATIENTS AND METHODS

We performed targeted error-corrected sequencing on samples from 1,727 donors age 40 years or older and assessed the effect of donor CH on recipient clinical outcomes. We measured long-term engraftment of 102 donor clones and cytokine levels in 256 recipients at 3 and 12 months after transplant.

RESULTS

CH was present in 22.5% of donors, with DNMT3A (14.6%) and TET2 (5.2%) mutations being most common; 85% of donor clones showed long-term engraftment in recipients after transplantation, including clones with a variant allele fraction < 0.01. DNMT3A-CH with a variant allele fraction ≥ 0.01, but not smaller clones, was associated with improved recipient overall (hazard ratio [HR], 0.79; P = .042) and progression-free survival (HR, 0.72; P = .003) after adjustment for significant clinical variables. In patients who received calcineurin-based graft-versus-host disease prophylaxis, donor DNMT3A-CH was associated with reduced relapse (subdistribution HR, 0.59; P = .014), increased chronic graft-versus-host disease (subdistribution HR, 1.36; P = .042), and higher interleukin-12p70 levels in recipients. No recipient of sole DNMT3A or TET2-CH developed donor cell leukemia (DCL). In seven of eight cases, DCL evolved from donor CH with rare TP53 or splicing factor mutations or from donors carrying germline DDX41 mutations.

CONCLUSION

Donor CH is closely associated with clinical outcomes in transplant recipients, with differential impact on graft alloimmune function and potential for leukemic transformation related to mutated gene and somatic clonal abundance. Donor DNMT3A-CH is associated with improved recipient survival because of reduced relapse risk and with an augmented network of inflammatory cytokines in recipients. Risk of DCL in allogeneic hematopoietic cell transplantation is driven by somatic myelodysplastic syndrome-associated mutations or germline predisposition in donors.

Donor Clonal Hematopoiesis and Recipient Outcomes After Transplantation

PURPOSE

Clonal hematopoiesis (CH) can be transmitted from a donor to a recipient during allogeneic hematopoietic cell transplantation. Exclusion of candidate donors with CH is controversial since its impact on recipient outcomes and graft alloimmune function is uncertain.

PATIENTS AND METHODS

We performed targeted error-corrected sequencing on samples from 1,727 donors age 40 years or older and assessed the effect of donor CH on recipient clinical outcomes. We measured long-term engraftment of 102 donor clones and cytokine levels in 256 recipients at 3 and 12 months after transplant.

RESULTS

CH was present in 22.5% of donors, with DNMT3A (14.6%) and TET2 (5.2%) mutations being most common; 85% of donor clones showed long-term engraftment in recipients after transplantation, including clones with a variant allele fraction < 0.01. DNMT3A-CH with a variant allele fraction ≥ 0.01, but not smaller clones, was associated with improved recipient overall (hazard ratio [HR], 0.79; P = .042) and progression-free survival (HR, 0.72; P = .003) after adjustment for significant clinical variables. In patients who received calcineurin-based graft-versus-host disease prophylaxis, donor DNMT3A-CH was associated with reduced relapse (subdistribution HR, 0.59; P = .014), increased chronic graft-versus-host disease (subdistribution HR, 1.36; P = .042), and higher interleukin-12p70 levels in recipients. No recipient of sole DNMT3A or TET2-CH developed donor cell leukemia (DCL). In seven of eight cases, DCL evolved from donor CH with rare TP53 or splicing factor mutations or from donors carrying germline DDX41 mutations.

CONCLUSION

Donor CH is closely associated with clinical outcomes in transplant recipients, with differential impact on graft alloimmune function and potential for leukemic transformation related to mutated gene and somatic clonal abundance. Donor DNMT3A-CH is associated with improved recipient survival because of reduced relapse risk and with an augmented network of inflammatory cytokines in recipients. Risk of DCL in allogeneic hematopoietic cell transplantation is driven by somatic myelodysplastic syndrome-associated mutations or germline predisposition in donors.