Stem cell transplantation for leukemias following myelodysplastic syndromes or secondary to cytotoxic therapy

Therapy-related Leukemia and Myelodysplasia: Evolving Concepts of Pathogenesis and Treatment

Therapy-related leukemia and therapy-related myelodysplasia (t-AML/MDS) are serious and increasingly frequent complications of cytotoxic chemotherapy and/or radiotherapy. Two syndromes can be distinguished, one of which has a long latency (5-7 years or more) and is seen following alkylating agents, frequently with an antecedent dysplastic phase. The other has a short latency period (1-3 years), no antecedent dysplastic phase, and is characteristically seen following topoisomerase II inhibitors. Chromosomal abnormalities can confirm t-leuk/MDS and are predictive of poor prognosis, particularly those involving gains and losses of chromosome 7. There is no standard therapy for t-AML/MDS. This review concentrates on the various treatment approaches for t-AML/MDS. Treatment can be aggressive, with curative intent, particularly for patients who are young with no end-organ damage from the prior malignancy or chemotherapy. Various chemotherapy regimens have been designed to overcome the chemoresistance which is generally characteristic of these syndromes. Bone marrow transplantation offers the best chance for cure, and both myeloablative and nonmyeloablative protocols have been designed. Low dose chemotherapy is an option for patients not able to withstand traditional curative regimens and supportive care is a legitimate option for elderly or infirm patients. Multicenter studies are urgently needed to provide data on which clearcut treatment guidelines can be based, taking into account the patient's age, disease status and risk factors.

Upfront allogeneic blood stem cell transplantation for patients with high-risk myelodysplastic syndrome or secondary acute myeloid leukemia using a FLAMSA-based high-dose sequential conditioning regimen

Patients suffering from high-risk myelodysplastic syndrome (MDS) or acute myelogenous leukemia (AML) secondary to MDS (sAML) are characterized by poor response to conventional cytotoxic chemotherapy. The purpose of our prospective single-center study was to examine the safety and efficacy of an allogeneic hematopoietic stem cell transplantation (HSCT) following a sequential conditioning regimen as first-line therapy for previously untreated patients with high-risk MDS or sAML. Between November 2003 and June 2010, 30 patients (20 high-risk MDS, 10 sAML) received fludarabine (4 × 30 mg/m(2)), amsacrine (4 × 100 mg/m(2)), and Ara-C (4 × 2 g/m(2), FLAMSA). After 2 to 3 days of rest, patients received high-dose melphalan alone (200 mg/m(2) for patients with an age <50 years, 150 mg/m(2) for patients with an age between 50 and 60 years, and 100 mg/m(2) for patients with an age >60 years; n = 24) or melphalan and thiotepa (10 mg/kg, Mel/Thio, n = 6). Following these high-dose conditioning regimens, a median number of 7.7 × 10(6) CD34(+) cells/kg body weight (range: 2.9 × 10(6)-17.2 × 10(6)) were transplanted from 13 related or 17 unrelated donors. Antithymocyte globulin (Fresenius 30-60 mg/kg) as well as tacrolimus and mycophenolate mofetil were used for graft-versus-host disease (GVHD) prophylaxis. All patients except 1 with primary graft failure achieved complete remission after HSCT. After a median follow-up time of 28 months (range: 7-81), 21 patients (70%) were alive and free of disease. Overall, 4 patients relapsed. At 2 years, overall survival, event-free survival, and treatment-related mortality were 70%, 63%, and 30%, respectively. Because of undue toxicity, thiotepa is no longer part of the conditioning regimen. Our results add to the body of evidence that a FLAMSA-based sequential conditioning therapy is effective for previously untreated patients with high-risk MDS or sAML.

[High risk of cardiac dysfunction after treatment of secondary acute myeloid leukemia following chemotherapy and radiotherapy for breast cancer]

Secondary acute myeloid leukaemia (AML) occurring after breast cancer is a rare long-term complication of the chemo- and/or radiation therapy required to treat breast cancer. The usually recognized curative option of these secondary AML includes courses of anthracycline-based chemotherapy followed by haematopoietic stem cell transplantation (HSCT). Cardiac dysfunction during AML treatment of these patients previously treated with anthracyclines for breast cancer has not been reported to date. We evaluated the evolution of cardiac function in seven patients treated with anthracyclines and/or autologous or allogeneic bone marrow transplantation for secondary AML occurring after breast cancer. All of the patients who received a cumulative anthracycline dose above the cardiac toxicity threshold developed cardiac symptoms during AML chemotherapy courses. Moreover, four of the five transplanted patients developed severe heart failure among which two were fatal. Thus, the risk of severe cardiac dysfunction after treatment of secondary AML following breast cancer must be taken in account as part of the therapeutic strategy of those patients. As discussed here, an accurate evaluation of risk factors, the use of sensitive detection tests and of cardioprotective drugs as well as that of non-cardiotoxic chemotherapy might decrease the occurrence and severity of this life-threatening complication.

Etoposide-initiated MLL rearrangements detected at high frequency in human primitive hematopoietic stem cells with in vitro and in vivo long-term repopulating potential

Rearrangements initiating within the well-characterized break-point cluster region of the mixed lineage leukemia (MLL) gene on 11q23 are a hallmark of therapy-related leukemias following treatment with topoisomerase II poisons including etoposide. Hematopoietic stem cells (HSC) are believed to be the target cell for leukemia-initiating MLL rearrangement events. Although etoposide treatment is sufficient to induce readily detectable MLL rearrangements in primary human CD34+ cells, the majority of cells that gain translocations do not proliferate in culture possibly due to reduced proliferative capacity of most CD34+ cells during normal differentiation [Blood 2005;105:2124]. We characterized the impact of etoposide on primary human long-term repopulating HSC that represent only a minor portion of CD34+ cells. The proliferative capacity of HSC is dramatically increased following both a single and multiple exposures to etoposide as determined by their ability to engraft bone marrow of immune-deficient non-obese diabetic/severe combined immunodeficient mice and to initiate hematopoiesis in long-term initiating cultures. Similar to results in CD34+ cells, a significant proportion of etoposide-treated HSC-derived clones harbored stable MLL rearrangements, including duplications, inversions and translocations. These results indicate HSC are highly susceptible to etoposide-induced and potentially oncogenic rearrangements initiating within MLL, and these HSC are particularly proficient for continued long-term proliferation both in vivo and in vitro.

Comparable non-relapse mortality and survival after HLA-identical sibling blood stem cell transplantation with reduced or conventional-intensity preparative regimens for high-risk myelodysplasia or acute myeloid leukemia in first remission

We prospectively compared two strategies of allogeneic PBSCT from HLA-identical siblings in adults with poor-risk AML or myelodysplastic syndrome with >5% marrow blasts in an early disease status (AML or refractory anemia with excess blasts (RAEB type 2) in first remission after chemotherapy or untreated RAEB type 1). Based only on age, all consecutive patients were offered one of two specific transplant protocols. Patients < or =50 years old received conventional high-dose conditioning with cyclophosphamide-TBI and use of CD34+-selected PBSCT (CTCD34+ group), while patients aged >50 years received a reduced-intensity conditioning (RIC) with fludarabine and oral busulphan (FB-RIC). Seventy-five patients entered the study (35 in the CTCD34+ and 39 in the FB-RIC group). The median follow-up was >4 years in both groups. The 4-year non-relapse mortality (NRM) was 19 and 20%, respectively (P=0.8). Relapse and survival were also equivalent in both groups. These results suggest that in this setting, the expected high NRM in elderly patients can be reduced with an RIC regimen.

Can reduced-intensity allogeneic transplantation cure older adults with AML?

Development of nonablative and reduced-intensity conditioning regimens has enabled older or medically infirm patients with myeloid malignancies to be treated with allogeneic hematopoietic cell transplantation (HCT). These regimens rely largely on graft-versus-leukemia effects rather than high-dose therapy to eliminate malignant cells. Studies indicate that there is sustained engraftment with relatively low transplant-related mortality in the small number of patients who have been treated. This review summarizes the outcome in recent studies of patients with myeloid malignancies who received HCT following nonmyeloablative or reduced-intensity conditioning. Comparison of nonmyeloablative with myeloablative transplant shows that the myeloablative patients are about 10-15 years younger. Toxicity is a major problem in the elderly who have comorbid conditions, but otherwise the patient has a similar outcome, again emphasizing the graft-versus-leukemia effect. Comparison of patients receiving related or unrelated grafts following nonmyeloablative conditioning shows that the outcome in these patients is similar. These studies have demonstrated encouraging overall survival and nonrelapse mortalities with evidence for graft-versus-leukemia responses in elderly patients with hematologic malignancies. Relapse and progressive disease continued to be problems, particularly in patients with large tumor burdens at time of HCT. Elimination of tumor burden prior to transplant with immunotherapy such as with radiolabeled anti-CD45 antibody or vaccines may improve outcome further.

Hematologic aspects of myeloablative therapy and bone marrow transplantation

The transplantation of bone marrow cells or isolated hematopoietic stem cells from the bone marrow or peripheral blood is a widely utilized form of therapy for patients with incurable diseases of the hematopoietic and immune systems. Successful engraftment of the transplanted stem cells in an adequately prepared recipient normally leads to bone marrow reconstitution over a period of several weeks, accompanied by more gradual reconstitution of the immune system. Since the recipient is profoundly ill during the initial treatment period, laboratory data is critical for monitoring engraftment, detecting residual/recurrent disease, and identifying problems that may delay bone marrow reconstitution or lead to other medical complications. Accurate blood cell counts are imperative, and most bone marrow transplantation patients undergo periodic monitoring with bone marrow aspirates and biopsies with cytogenetic, molecular, and multiparametric flow cytometric studies. The potential complications of bone marrow transplantation include engraftment failure and delayed engraftment, infection, residual bone marrow disease, acute and chronic graft versus host disease, myelofibrosis, therapy-related acute leukemia, post-transplant lympho-proliferative disorders, and toxic myelopathy.