Bone marrow aspirates as part of routine donor assessment for allogeneic blood and marrow transplantation can reveal presence of occult hematological malignancies in otherwise asymptomatic individuals

Genetic Findings of Potential Donor Origin following Hematopoietic Cell Transplantation: Recommendations on Donor Disclosure and Genetic Testing from the World Marrow Donor Association

Following hematopoietic cell transplantation (HCT), recipients are subjected to extensive genetic testing to monitor the efficacy of the transplantation and identify relapsing malignant disease. This testing is increasingly including the use of large gene panels, which may lead to incidental identification of genetic and molecular information of potential donor origin. Deciphering whether variants are of donor origin, and if so, whether there are clinical implications for the donor can prove challenging. In response to queries from donor registries and transplant centers regarding best practices in managing donors when genetic mutations of potential donor origin are identified, the Medical Working Group of the World Marrow Donor Association established an expert group to review available evidence and develop a framework to aid decision making. These guidelines aim to provide recommendations on predonation consenting, postdonation testing of recipients, and informing and managing donors when findings of potential donor origin are identified in recipients post-transplantation. It is recognized that registries will have different access to resources and financing structures, and thus whenever possible, we have made suggestions on how recommendations can be adapted.

Systematic Scoping Review of Studies Reporting Unexpected Donor-Derived Abnormalities from Recipients of Allogeneic Hematopoietic Cell Transplantation: A Proposed Framework for Donor Disclosure

Allogeneic hematopoietic cell transplantation (HCT) is used increasingly to treat blood and immune-based disorders. Post-transplantation testing of HCT recipients can lead to unexpected molecular, cytogenetic, and other information in donor-derived cells, raising questions regarding the potential impact on donor health. This study was conducted to identify the breadth of donor-derived abnormalities identified by testing HCT recipients and to determine the extent to which disclosure and donor follow-up are described. A systematic search and scoping review were conducted following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) extension for scoping review guidelines in OVID MEDLINE and Embase (1947 to May 24, 2021). We identified 38 studies (63 donor-recipient pairs) addressing nonleukemic abnormalities to complement existing literature describing donor cell leukemia and donor-derived myelodysplasia. Donors were unrelated adults (n = 20), related family members (n = 28), cord blood donors (n = 6), or not reported (n = 9). Acquired cytogenetic, molecular, and morphologic abnormalities were reported. Donor origin was confirmed by cytogenetic analysis via karyotyping, fluorescence in situ hybridization, single tandem repeat PCR, and other techniques. A disease in donor-derived cells was described in 35 recipients (56.5%). Despite the relevance for testing and disclosure to donors, only 22 cases (32%) mentioned donor follow-up, and in 5 cases the donor developed a disease associated with the identified abnormality. Unrelated donor disclosure was mentioned in 3 of 26 cases (12%), with the findings reported back to the registry. Incidental abnormalities identified in transplanted donor cells may contribute to the post-transplantation risk of illness in the recipient and may be relevant to donor health. A framework for donor disclosure is proposed that incorporates consideration of analytic validity of the testing, potential significance of the finding, and the extent to which the abnormality is actionable. Adoption of effective processes to safeguard both donor and recipient health outcomes related to this issue is needed.

Influence of the degree of donor bone marrow hyperplasia on patient clinical outcomes after allogeneic hematopoietic stem cell transplantation

This study evaluated the influence of the degree of donor bone marrow (BM) hyperplasia on patient clinical outcomes after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Twelve patients received allo-HSCT from hypoplastic BM donors between January 2010 and December 2017. Forty-eight patients whose donors demonstrated BM hyperplasia were selected using a propensity score matching method (1:4). Primary graft failure including poor graft function and graft rejection did not occur in two groups. In BM hypoplasia and hyperplasia groups, the cumulative incidence (CI) of neutrophil engraftment at day 28 (91.7% vs. 93.8%, P=0.75), platelet engraftment at day 150 (83.3% vs. 93.8%, P=0.48), the median time to myeloid engraftment (14 days vs. 14 days, P=0.85) and platelet engraftment (14 days vs. 14 days, P=0.85) were comparable. The 3-year progression-free survival, overall survival, CI of non-relapse mortality and relapse were 67.8% vs. 71.7% (P=0.98), 69.8% vs. 77.8% (P=0.69), 18.5% vs. 13.6% (P=0.66), and 10.2% vs. 10.4% (P=0.82), respectively. In multivariate analysis, donor BM hypoplasia did not affect patient clinical outcomes after allo-HSCT. If patients have no other suitable donor, a donor with BM hypoplasia can be used for patients receiving allo-HSCT if the donor Complete Blood Count and other examinations are normal.

Inversion 3 Cytogenetic Abnormality in an Allogeneic Hematopoietic Cell Transplant Recipient Representative of a Donor-Derived Constitutional Abnormality

Allogeneic hematopoietic cell transplantation (HCT) is an important treatment for many severe hematologic disorders; however, HCT can be associated with significant complications, including organ toxicity, graft-versus-host disease, and relapse. Another serious, but rare, complication is the transmission of hematologic and nonhematologic diseases from the donor to the recipient. With older donors, the risk of an abnormality may be increased. Here we describe the transmission of an inversion 3 constitutional cytogenetic abnormality from an unrelated donor to a recipient, and review the clinical implications of the discovery of donor-derived constitutional cytogenetic abnormalities.

Sixty as the new forty: considerations on older related stem cell donors

The era of reduced-intensity allogeneic stem cell transplantation, with its emphasis on older patients, has created new challenges in the management of what is now an older related stem cell donor population. These donors are now on average no less than 10 years older than in the mid-1990s. Donors over 70 years of age are no longer isolated or exceptional cases. They may still be considered eligible for donation but many of them, based on the older age and their medical history, may no longer fully qualify as 'healthy' or 'normal'. The older the donor, the more likely that hematologic abnormalities, comorbidities and treated malignancies will complicate the picture. Assessing the risk-benefit ratio for both donor and recipient can now be more challenging than ever.

Transmission of an expanding donor-derived del(20q) clone through allogeneic hematopoietic stem cell transplantation without the development of a hematologic neoplasm

Donor cell leukemia is a rare complication of allogeneic hematopoietic stem cell transplantation (HSCT), which may result from the development of a new malignancy in previously healthy donor cells after transplant into the recipient, or it may derive from the transmission of an occult leukemia from donor to recipient. We report a case of donor derived 20q11.2 deletion in a male patient who received an allogeneic HSCT from his HLA-identical sister for the treatment of his chronic lymphocytic leukemia. Bone marrow cells from the donor were found to contain the 20q deletion that expanded over time, but which was absent in her peripheral blood cells. Although cases of donor cell leukemia after HSCT have been reported, in this case there has been no evidence of an associated hematologic neoplasm in either the donor or recipient. Pre-transplant donor bone marrow evaluations are not practical or warranted, however the finding of new cytogenetic abnormalities after transplant mandates a thorough evaluation of the donor.

Targeted pathologic evaluation of bone marrow donors identifies previously undiagnosed marrow abnormalities

Potential bone marrow donors are screened to ensure the safety of both the donor and recipient. At our institution, potential donors with abnormal peripheral blood cell counts, a personal history of malignancy, or age >60 years are evaluated to ensure that they are viable candidates for donation. Evaluation of the marrow includes morphologic, flow cytometric, and cytogenetic studies. A total of 122 potential donors were screened between the years of 2001 and 2011, encompassing approximately 10% of all donors. Of the screened potential donors, the mean age was 59 years and there were 59 men and 63 women. The donors were screened because of age >60 years (n = 33), anemia (n = 22), cytopenias other than anemia (n = 27), elevated peripheral blood counts without a concurrent cytopenia (n = 20), elevated peripheral blood counts with a concurrent cytopenia (n = 10), history of malignancy (n = 4), abnormal peripheral blood differential (n = 3), prior graft failure (n = 1), history of treatment with chemotherapy (n = 1), and body habitus (n = 1). Marrow abnormalities were detected in 9% (11 of 122) of donors. These donors were screened because of anemia (5 of 22, 23%), age >60 years (2 of 33, 6%), history of malignancy (2 of 4, 50%), elevated peripheral blood counts (1 of 20, 5%), and body habitus (1 of 1, 100%). Abnormalities included plasma cell dyscrasia (n = 3), abnormal marrow cellularity (n = 3), clonal cytogenetic abnormalities (n = 2), low-grade myelodysplastic syndrome (1), a mutated JAK2 V617F allele (n = 1), and monoclonal B cell lymphocytosis (n = 1). Our experience indicates that extended screening of potential donors identifies a significant number of donors with previously undiagnosed marrow abnormalities.

Donor cell leukemia: a review

Relapse of acute leukemia following hematopoietic stem cell transplantation (HSCT) usually represents return of an original disease clone, having evaded eradication by pretransplant chemo-/radiotherapy, conditioning, or posttransplant graft-versus-leukemia (GVL) effect. Rarely, acute leukemia can develop de novo in engrafted cells of donor origin. Donor cell leukemia (DCL) was first recognized in 1971, but for many years, the paucity of reported cases suggested it to be a rare phenomenon. However, in recent years, an upsurge in reported cases (in parallel with advances in molecular chimerism monitoring) suggest that it may be significantly more common than previously appreciated; emerging evidence suggests that DCL might represent up to 5% of all posttransplant leukemia "relapses." Recognition of DCL is important for several reasons. Donor-derivation of the leukemic clone has implications when selecting appropriate therapy, because seeking to enhance an allogeneic GVL effect would intuitively not have the same role as in standard recipient-derived relapses. There are also broader implications for donor selection and workup, particularly given the growing popularity of nonmyeloblative HSCT and corresponding rising age of the potential donor pool. Identification of DCL raises potential concerns over future health of the donor, posing ethical dilemmas regarding responsibilities toward donor notification (particularly in the context of cord blood transplantation). The entity of DCL is also of research interest, because it might provide a unique human model for studying the mechanisms of leukemogenesis in vivo. This review presents and collates all reported cases of DCL, and discusses the various strategies, controversies, and pitfalls when investigating origin of posttransplant relapse. Putative etiologic factors and mechanisms are proposed, and attempts made to address the difficult ethical questions posed by discovery of donor-derived malignancy within a HSCT recipient.

Bioethical considerations of monoclonal B-cell lymphocytosis: donor transfer after haematopoietic stem cell transplantation

Monoclonal B-cell lymphocytosis (MBL) is a recently described laboratory finding in otherwise healthy individuals. In MBL, a light chain-restricted, clonal B-cell population, often with a chronic lymphocytic leukaemia (CLL) phenotype, is identified by flow cytometry. Although the prognostic significance remains unclear, there is an increased incidence in ageing populations and those with a family history of CLL. During the past decade of MBL study, three families have come to our attention in which prospective sibling haematopoietic stem cell donors were found to have an MBL. These families raise complex bioethical issues with regard to disclosure of research data, eligibility for clinical trials and potential donor transfer of MBL. These issues are explored in this report. Identification of MBL among prospective sibling transplant donors will become a common occurrence in transplant practice as transplantation is increasingly offered to older individuals and those with CLL.

Genetically identical twin transplantation for chronic lymphocytic leukemia

We identified 19 persons with B-cell chronic lymphocytic leukemia (CLL) who received genetically identical twin blood cell or bone marrow transplants after high-dose conditioning. Ten are alive (eight disease-free) with a median follow-up of 89 months (range, 31-171 months); 5-year relapse rate was 50% (95% confidence interval (CI), 26-73%). Estimated 5-year survival and disease-free survival were 61% (95% CI, 37-82%) and 45% (95% CI, 23-68%). In two of four patients tested at 12 and 21 months by polymerase chain reaction no evidence of residual CLL was detected post-transplant. In one recipient who relapsed at 6 years, molecular studies showed a different CLL clone from that detected pretransplant. This clone was subsequently identified in the donor suggesting transfer of occult leukemia at the time of transplant. Genetically identical twin transplants can result in long-term disease-free survival and molecular remissions, these data suggest the potential for CLL control in the absence of allogeneic graft-versus-leukemia effect. The case of leukemia transfer indicates the need for careful evaluation of donors prior to graft collection.

Long-term donor health and its relationship with outcome of allogeneic hematopoietic stem cell transplantation

Data on long-term follow-up of donors for hematopoietic stem cell transplantation (HSCT) are limited. Donors of 612 adult allogeneic HSCT were studied, at a median of 81 (14-181) months post-HSC donation. Nine donors had severe health problems. Five donors died from aggressive malignancies or terminal illness, at a median of 41 (16-57) months post-donation. Notably, all their recipients had leukemic relapses. In contrast, donors of recipients in remission were all living. This observation might be due to an inherent depressed immunosurveillance in the donors, or selection of donors with suboptimal health for desperate patients with poor risks pre-HSCT.

Nonmyeloablative Stem Cell Transplantation for Myelodysplastic Syndrome or Acute Myeloid Leukemia in Patients 60 Years or Older

We analyzed the outcomes of 24 consecutive patients aged >or=60 years with poor-prognosis myelodysplastic syndrome or acute myeloid leukemia undergoing transplantation with nonmyeloablative conditioning using fludarabine (125 mg/m2) and low-dose total body irradiation (2 Gy) followed by allogeneic peripheral blood stem cell grafts from HLA-identical sibling donors. Graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine and mycophenolate mofetil. The median age of the patients was 64 years (range, 60-71 years). In addition to age, 88% of patients had 1 or more adverse biological features of the disease. With a median follow-up of 21 months, 12 patients are alive, 11 of whom are disease free. The probabilities of 2-year overall and progression-free survival were 52% and 44%, respectively. The cumulative probabilities of relapse and of acute and chronic GVHD were 27%, 45%, and 74%, respectively. Nonrelapse mortality at 100 days and 2 years was 8% and 25%, respectively. Of the 15 patients with extensive chronic GVHD, 1 patient relapsed. These data suggest that nonmyeloablative stem cell transplantation is a feasible treatment option in patients aged >or=60 years with poor-prognosis myelodysplastic syndrome or acute myeloid leukemia. The reasonable disease control with nonmyeloablative transplantation in this high-risk group of patients merits further investigation.

A novel chromosomal abnormality, t(6;10)(q27;q22), found in a polycythemic potential donor for allogeneic hematopoietic stem cell transplantation

A 59-year-old man was a potential donor for allogeneic hematopoietic stem cell transplantation and was found to be healthy but slightly polycythemic. The bone marrow was morphologically normal, but karyotyping of bone marrow cells showed t(6;10)(q27;q22) in 7 of 20 metaphases analyzed by G-banding and only the t(6;10) abnormality in 3 of 5 metaphases analyzed by the spectral karyotyping method. G-banding analysis of peripheral blood mononuclear cells cultured with phytohemagglutinin for 72 hours showed a normal karyotype in all 20 metaphases analyzed.These findings suggest clonal expansion with t(6;10)(q27;q22) in the bone marrow of this individual. He was determined to be ineligible for donation. A coordinated nationwide work-up for older donors is necessary to ensure high-quality standards.

Transmission of donor illness by stem cell transplantation: should screening be different in older donors?

With increasing donor age, the potential of transmitting diseases from donor to recipient reaches new dimensions. Potentially transmittable diseases from donors include infections, congenital disorders, and acquired illnesses like autoimmune diseases or malignancies of hematological or nonhematological origin. While established nonmalignant or malignant diseases might be easy to discover, early-stage hematological diseases like CML, light-chain multiple myelomas, aleukemic leukemias, occult myelodysplastic syndromes and other malignant and nonmalignant diseases might not be detectable by routine screening but only by invasive, new and/or expensive diagnostic tests. In the following article, we propose recommendations for donor work-up, taking into consideration the age of the donors. In contrast to blood transfusions, stem cells from donors with abnormal findings might still be acceptable for HCT, when no other options are available and life expectancy is limited. This issue is discussed in detail in relation to the available donor and stem cell source. Finally, the recommendations presented here aim at harmonized worldwide work-up for donors to insure high standard quality.