Treosulfan-Based Conditioning Regimen in Sibling and Alternative Donor Hematopoietic Stem Cell Transplantation for Children with Sickle Cell Disease.

BACKGROUND AND OBJECTIVES: Lack of suitable donors and regimen related toxicity are major barriers for hematopoietic stem cell transplantation (HSCT) in patients with sickle cell disease (SCD). The aim of the study is the assessment of efficacy and toxicity of Treosulfan-based conditioning regimen for SCD also when alternative donors such as mismatched unrelated donor and haploidentical donor are employed. METHODS: We report our single-center experience: 11 patients with SCD received HSCT with a Treosulfan/Thiotepa/Fludarabine/Anti-thymoglobulin conditioning regimen between 2010 and 2015. The donor was a matched sibling donor (n= 7), a haploidentical parent (n= 2), a matched unrelated donor (n= 1) or a mismatched unrelated donor (n=1). The haploidentical and mismatched unrelated donor grafts were manipulated by removing TCRαß and CD19 positive cells. RESULTS: All patients survived the procedure and achieved stable engraftment. Stable mixed chimerism was observed in 5/11 patients. Grade III-IV regimen related toxicity was limited to mucositis and no grade III-IV graft-versus-host disease (GvHD) occurred. No SCD manifestation was observed post transplant and cerebral vasculopathy improved in 3/5 evaluable patients. Organ function evaluation showed no pulmonary, cardiac or renal toxicity but gonadal failure occurred in 1/4 evaluable patients. CONCLUSION: Our data suggest that Treosulfan is associated with low toxicity and may be employed also for unrelated and haploidentical donor HSCT.

Chemosensitivity of nonleukemic clonogenic precursors in AML patients in complete remission: association with CD34(+) mobilization and with disease-free survival.

A high number of CD34(+) cells in the peripheral blood during mobilization in patients with acute myeloid leukemia (AML) in complete remission (CR) is associated with a high relapse rate. The variability in chemoresistance of normal bone marrow precursors has been hypothesized as explanation for the variable CD34 mobilization in AML. In 37 patients with AML in CR, we determined the chemosensitivity of bone marrow clonogenic precursors to maphosphamide and etoposide, which was then correlated with the degree of CD34(+) mobilization. In an enlarged set of 49 patients, we also studied the importance of chemosensitivity of marrow precursors for disease-free survival and relapse incidence. Significant correlations were demonstrated between the peak number of CD34(+) cells and residual growth of colony-forming unit granulocyte-macrophage (CFU-GM) after maphosphamide (R = 0.550; p = 0.0003) and after etoposide (R = 0.793; p = 0.0003). It was possible to identify three groups of AML patients based on chemosensitivity. The mean CD34(+) peak was 33 × 10(6)/L in the hyperchemosensitive group, 141 × 10(6)/L in the normochemosensitive (p = 0.03), and 379 × 10(6)/L in the chemoresistant group (p = 0.002). Failed CD34(+) mobilization was observed in 72% of the hyperchemosensitive group, 23% of the normochemosensitive group, and 0% of the chemoresistant group (p = 0.001). Hyperchemosensitivity of CFU-GM, together with a low platelet count, were independent factors important in the failure of CD34(+) cell mobilization. A disease-free survival significantly inferior to that of all other patients was associated with chemoresistance of CFU-GM (log rank, p = 0.030) and with chemoresistance of burst-forming unit erythroid (BFU-E) (log rank, p = 0.033). Chemoresistance of CFU-GM (p = 0.048) and BFU-E (p = 0.017) was also associated with increase relapse incidence. Nonleukemic nature of these precursors was demonstrated studying minimal residual disease from single colony cells. In conclusion, we found that hyperchemosensitivity of normal nonleukemic CFU-GM is associated with a high risk of CD34(+) cell mobilization failure, while a chemoresistant pattern in CFU-GM and BFU-E is associated with poor disease-free survival and increased cumulative incidence of relapse.

Intermediate dose etoposide plus G-CSF 16 g/kg is more effective than cyclophosphamide 4 g/m(2) plus G-CSF 10 g/kg in PBSC mobilization of lymphoma patients.

We designed intermediate dose etoposide + G-CSF 16 microg/kg as a Peripheral Blood Stem Cell (PBSC) mobilization schedule suitable for outpatient administration. Forty-one Lymphoma patients received intermediate dose etoposide (200 mg/m(2) i.v. day +1, +2, +3) +G-CSF 16 microg/kg/day. Results of PBSC mobilization in these patients were compared with those of a group of 37 lymphoma patients mobilized using cyclophosphamide (CTX) at dosage of 4 g/m(2) + G-CSF 10 microg/kg/die. Mean peak of CD34+ cells achieved in P.B. and total CD34+ cells harvested were higher in patients mobilized with intermediate dose etoposide (p = 0.003 and p = 0.004, respectively). After transplantation recovery of polymorphonucleate neutrophils (PMN) > 0.5 x 10(9)/L did not differ significantly between groups: 11.7 days in intermediate dose etoposide group and 11.5 days in CTX group (p = 0.7). Intermediate dose etoposide + G-CSF 16 microg/kg resulted in a maximum length of neutropenia (PMN < 0.5 x 10(9)/L) of 2 days and neutropenic fever was registered during only 3/41 courses (7.3%). Intermediate dose etoposide + G-CSF 16 microg/kg is a highly effective mobilizing therapy, further, it has the advantage of low hematologic toxicity and can be easily administered as outpatient treatment.