Chimerism studies with quantitative real-time PCR in stem cell recipients with acute myeloid leukemia.

OBJECTIVE: Chimerism is well-established for surveillance of acute myeloid leukemia (AML) patients after allogeneic hematopoietic stem cell transplantation (HSCT), but interpretation of the results and techniques is not standardized. MATERIALS AND METHODS: We correlated chimerism in 75 AML patients (38 male, 37 female) who underwent myeloablative (n = 36)/reduced (n = 39) allo-HSCT with the risk of relapse and survival. Chimerism was evaluated by quantitative real-time polymerase chain reaction for donor/recipient specific polymorphisms/Y-specific sequences. RESULTS: After HSCT, 40 patients (53%) achieved stable complete donor chimerism (≥ 99.0% of donor alleles), while 35 (47%) failed to achieve stable donor chimerism. Thirty-one patients (41%) showed decreasing donor alleles after having first achieved complete donor chimerism. To investigate the kinetics of mixed chimerism, patients were separated whether they showed subsequent increasing or decreasing donor alleles. Subsequent decrease of donor alleles was associated with relapses in 17 of 18 cases (94%), while no patient with subsequent increasing donor alleles relapsed (p < 0.001). Patients with mixed chimerism and increasing donor alleles had better 2-year disease-free survival (85%) than those with decreasing donor alleles (0%; p < 0.001). CONCLUSIONS: The kinetics of mixed chimerism as assessed by quantitative real-time polymerase chain reaction is an important prognostic predictor in the post-transplantation period of AML patients.

Post-transplant immune reconstitution after unrelated allogeneic stem cell transplant in patients with acute myeloid leukemia.

We evaluated immune recovery in 67 patients with acute myeloid leukemia (AML) with a median age of 40 years (4-69) following allo-SCT after reduced (n = 35) or myeloablative (n = 32) conditioning. The following lymphocyte populations were determined on days +30, +90, +180, +270, and +365 by flow associated cell sorting: CD3+, CD3+CD4+, CD3+CD8+, CD3+CD4+/CD3+CD8+ ratio, CD3-CD56+, and CD19+ cells. Peripheral blast count >5% was related to lower number of CD3+CD4+ (day +30) and NK cells (day +180; p = 0.02). Intensity of conditioning did not have any significant impact on the kinetics of immune recovery. Patients with normal CD3+CD4+/CD3+CD8+ ratio (day +30) and NK cell count (day +90; p <0.05) experienced better survival than those with decreased parameters. Post-transplant sepsis/severe infections impaired CD3+CD8+ (day +90; p = 0.015) and CD19+ (day +90; p = 0.02) recovery. Relapse in patients following allo-SCT showed an association with decreased numbers of CD19+ (day +270) and NK cells (day +365). Acute GvHD (II-IV) was accompanied by reduced CD19+ and CD3+CD4+ cells. Thus, the evaluation of post-transplant immune reconstitution in patients with AML might improve risk stratification concerning either relapse or TRM and remains to be further explored.

Diagnostic tools in the indications for allogeneic stem cell transplantation in myelodysplastic syndromes.

The rates of allogeneic stem cell transplantation (SCT) to treat the myelodysplastic syndromes (MDS) is continually increasing. However, given the growing arsenal of therapeutic options in parallel to deeper insight into the heterogeneity of this disorder, determining the indications for SCT in MDS remains a difficult task. The International Prognostic Scoring System (IPSS) serves as a guideline for therapeutic decisions, but many aspects (eg, interpretation of rare cytogenetic abnormalities, combinations of chromosomal alterations and/or molecular markers, variant clinical courses within distinct biological subgroups) remain the subject of continuous investigation. In an effort to achieve a more well-differentiated risk categorization, attempts have been made to perform a more detailed cytogenetic categorization, and the use of various fluorescein in situ hybridization (FISH) techniques has improved the description of aberrations. Multicenter initiatives have standardized multiparameter flow cytometry techniques for diagnosis of MDS. In advanced MDS, screening for molecular mutations can identify cases with a high transformation risk. Finally, the new World Health Organization classification system provides a more homogenous morphological categorization of MDS compared with the former French-American-British system. Consequently, in the near future, risk stratification in MDS might incorporate additional diagnostic tools and categorization systems aimed at improving the timing and indication for SCT in this complex disorder.

Current status and perspectives of tyrosine kinase inhibitor treatment in the posttransplant period in patients with chronic myelogenous leukemia (CML).

Following the introduction of tyrosine kinase inhibitors (TKIs) in chronic myelogenous leukemia (CML), allogeneic stem cell transplantation (SCT) took a shift toward high-risk patients. Considering the high relapse rates posttransplant in these selected patients, several studies evaluated posttransplant use of the TKI imatinib. Although the number of studies are still limited, and data have to be confirmed by additional studies, safety of imatinib even within the first months after SCT seems to be acceptable. Imatinib was shown to be effective in patients with molecular or hematologic relapse of chronic or accelerated phase posttransplant (CP, AP), whereas outcomes in blast phase were more unfavorable. The compound further seemed beneficial for prophylactic use in patients who achieved complete remission posttransplant. The combination of imatinib with donor lymphocytes did not result in increased toxicity or graft-versus-host disease (GVHD). First studies suggest that second-generation TKIs such as dasatinib or nilotinib are manageable posttransplant with acceptable toxicity as well. In conclusion, TKIs of the first- and second-generation are promising options for the posttransplant period of patients with CML, but algorithms for dosage, intervals from SCT, duration of application, and the combination with donor lymphocytes still have to be developed.

Second allogeneic stem cell transplantation in myeloid malignancies.

For patients with myeloid malignancies who relapse after allogeneic stem cell transplantation (allo-SCT), one salvage option is a second SCT. We retrospectively analyzed outcomes of the second allo-SCT in 25 patients who received at least 2 allografts from related/unrelated donors due to relapse of acute myeloid leukemia, myelodysplastic syndrome or myelofibrosis after the first SCT. A minority of the acute myeloid leukemia/myelodysplastic syndrome patients had reached complete hematological remission before the second SCT (6/25, 24%). Reduced conditioning strategies were performed in the majority (n = 23). Complete remission was achieved in all 21 cases with available data after the second SCT, but relapse was seen in 11/25 patients (44%). After a median follow-up of 18 months (range 6-47), 8/25 patients (32%) were still alive, and of those, 6 (24%) were in stable remission. In 9 cases mortality was associated to relapse and in 8 cases to transplant-related causes (treatment-related mortality; 8/25, 32%). In conclusion, a second SCT offers the chance of stable remission for some patients relapsing with a myeloid malignancy after a first allo-SCT, although high treatment-related mortality and relapse rates remain a problem. Efforts should concentrate on an optimization of conditioning strategies, immunosuppression and post-transplant surveillance for this specific situation.

Safety of conditioning agents for allogeneic haematopoietic transplantation.

Allogeneic stem cell transplantation (allo-SCT) for haematological malignancies became a safer approach in recent years, for example, owing to improved supportive strategies. However, despite the efficacy of the procedure, morbidity and mortality mainly caused by infections and organ toxicity remain serious problems. Due to the variety of conditioning regimens being applied before allo-SCT, one important aspect is represented by the toxicity profiles of the specific compounds, which are being applied for the reduction of the leukaemia cell load and for immunosuppression. This is being illustrated by the hepatotoxic profile of busulfan with its high rate of veno-occlusive disease. However, recent advances in our understanding of drug metabolism, progress in the measurement of drug concentration, and the invention of some new drugs and therapeutic approaches in the conditioning period are promising steps in achieving more safety for patients undergoing allo-SCT. Reduced-intensity conditioning concepts allow the inclusion of heavily pretreated patients or patients with severe co-morbidities in transplantation concepts. New prophylactic regimens, including poly- or monoclonal antibodies, result in reduced rates of graft-versus-host disease, and some 'new' drugs such as treosulfan or clofarabine widen the range of available conditioning regimens for specific situations.