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Measurable residual disease (MRD) measured using multiparameter flow-cytometry (MFC) has proven to be an important prognostic biomarker in acute myeloid leukemia (AML). In addition, MRD is increasingly used to guide consolidation treatment towards a non-allogenic stem cell transplantation treatment for MRD-negative patients in the ELN-2017 intermediate risk group. Currently, measurement of MFC-MRD in bone marrow is used for clinical decision making after 2 cycles of induction chemotherapy. However, measurement after 1 cycle has also been shown to have prognostic value, so the optimal time point remains a question of debate. We assessed the independent prognostic value of MRD results at either time point and concordance between these for 273 AML patients treated within and according to the HOVON-SAKK 92, 102, 103 and 132 trials. Cumulative incidence of relapse, event free survival and overall survival were significantly better for MRD-negative (<0.1%) patients compared to MRD-positive patients after cycle 1 and cycle 2 (p ≤ 0.002, for all comparisons). A total of 196 patients (71.8%) were MRD-negative after cycle 1, of which the vast majority remained negative after cycle 2 (180 patients; 91.8%). In contrast, of the 77 MRD-positive patients after cycle 1, only 41 patients (53.2%) remained positive. A cost reduction of –€571,751 per 100 patients could be achieved by initiating the donor search based on the MRD-result after cycle 1. This equals to a 50.7% cost reduction compared to the current care strategy in which the donor search is initiated for all patients. These results show that MRD after cycle 1 has prognostic value and is highly concordant with MRD status after cycle 2. When MRD-MFC is used to guide consolidation treatment (allo vs non-allo) in intermediate risk patients, allogeneic donor search may be postponed or omitted after cycle 1. Since the majority of MRD-negative patients remain negative after cycle 2, this could safely reduce the number of all

Measurable residual disease (MRD) measured using multiparameter flow-cytometry (MFC) has proven to be an important prognostic biomarker in acute myeloid leukemia (AML). In addition, MRD is increasingly used to guide consolidation treatment towards a non-allogenic stem cell transplantation treatment for MRD-negative patients in the ELN-2017 intermediate risk group. Currently, measurement of MFC-MRD in bone marrow is used for clinical decision making after 2 cycles of induction chemotherapy. However, measurement after 1 cycle has also been shown to have prognostic value, so the optimal time point remains a question of debate. We assessed the independent prognostic value of MRD results at either time point and concordance between these for 273 AML patients treated within and according to the HOVON-SAKK 92, 102, 103 and 132 trials. Cumulative incidence of relapse, event free survival and overall survival were significantly better for MRD-negative (<0.1%) patients compared to MRD-positive patients after cycle 1 and cycle 2 (p ≤ 0.002, for all comparisons). A total of 196 patients (71.8%) were MRD-negative after cycle 1, of which the vast majority remained negative after cycle 2 (180 patients; 91.8%). In contrast, of the 77 MRD-positive patients after cycle 1, only 41 patients (53.2%) remained positive. A cost reduction of -€571,751 per 100 patients could be achieved by initiating the donor search based on the MRD-result after cycle 1. This equals to a 50.7% cost reduction compared to the current care strategy in which the donor search is initiated for all patients. These results show that MRD after cycle 1 has prognostic value and is highly concordant with MRD status after cycle 2. When MRD-MFC is used to guide consolidation treatment (allo vs non-allo) in intermediate risk patients, allogeneic donor search may be postponed or omitted after cycle 1. Since the majority of MRD-negative patients remain negative after cycle 2, this could safely reduce the number of allogenei

Lenalidomide, an antineoplastic and immunomodulatory drug, has therapeutic activity in acute myeloid leukemia (AML), but definitive studies about its therapeutic utility have been lacking. In a phase 3 study, we compared 2 induction regimens in newly diagnosed patients age 18 to 65 years with AML: idarubicine-cytarabine (cycle 1) and daunorubicin and intermediate-dose cytarabine (cycle 2) without or with lenalidomide (15 mg orally on days 1-21). One final consolidation cycle of chemotherapy or autologous stem cell transplantation (auto-SCT) or allogeneic SCT (allo-SCT) was provided according to a prognostic risk and minimal residual disease (MRD)-adapted approach. Event-free survival (EFS; primary end point) and other clinical end points were assessed. A second random assignment in patients in complete response or in complete response with incomplete hematologic recovery after cycle 3 or auto-SCT involved 6 cycles of maintenance with lenalidomide (10 mg on days 1-21) or observation. In all, 392 patients were randomly assigned to the control group, and 388 patients were randomly assigned to lenalidomide induction. At a median follow-up of 41 months, the study revealed no differences in outcome between the treatments (EFS, 44% ± 2% standard error and overall survival, 54% ± 2% at 4 years for both arms) although in an exploratory post hoc analysis, a lenalidomide benefit was suggested in SRSF2-mutant AML. In relation to the previous Dutch-Belgian Hemato-Oncology Cooperative Group and Swiss Group for Clinical Cancer Research (HOVON-SAKK) studies that used a similar 3-cycle regimen but did not pursue an MRD-guided approach, these survival estimates compare markedly more favorably. MRD status after cycle 2 lost prognostic value in intermediate-risk AML in the risk-adjusted treatment context. Maintenance with lenalidomide showed no apparent effect on relapse probability in 88 patients randomly assigned for this part of the study.

BACKGROUND: Haplo-identical hematopoietic stem cell (HSC) transplantation is very successful in eradicating haematological tumours, but the long post-transplant T-lymphopenic phase is responsible for high morbidity and mortality rates. Clark et al. have described a skin-explant system capable of producing host-tolerant donor-HSC derived T-cells. Because this T-cell production platform has the potential to replenish the T-cell levels following transplantation, we set out to validate the skin-explant system. RESULTS: Following the published procedures, while using the same commercial components, it was impossible to reproduce the skin-explant conditions required for HSC differentiation towards mature T-cells. The keratinocyte maturation procedure resulted in fragile cells with minimum expression of delta-like ligand (DLL). In most experiments the generated cells failed to adhere to carriers or were quickly outcompeted by fibroblasts. Consequently it was not possible to reproduce cell-culture conditions required for HSC differentiation into functional T-cells. Using cell-lines over-expressing DLL, we showed that the antibodies used by Clark et al. were unable to detect native DLL, but instead stained 7AAD+ cells. Therefore, it is unlikely that the observed T-lineage commitment from HSC is mediated by DLL expressed on keratinocytes. In addition, we did confirm expression of the Notch-ligand Jagged-1 by keratinocytes. CONCLUSIONS: Currently, and unfortunately, it remains difficult to explain the development or growth of T-cells described by Clark et al., but for the fate of patients suffering from lymphopenia it is essential to both reproduce and understand how these co-cultures really "work". Fortunately, alternative procedures to speed-up T-cell reconstitution are being established and validated and may become available for patients in the near future.

Mucin-1 (MUC1) is a heavily O-glycosylated, transmembrane protein that is expressed on the apical surface of most secretory epithelia. In malignantly transformed epithelia, MUC1 has lost its apical distribution, is underglycosylated and is secreted into the circulation. Due to the underglycosylation of MUC1, cancer-specific MUC1-Tn/STn antigens, which are highly immunogenic, become exposed. We aimed at developing a system that allows detection of antibodies directed to the native form of MUC1 and the underglycosylated MUC1-Tn epitopes. To this end, we made use of the Chinese Hamster Ovary (CHO) ldlD cell line stably transfected with MUC1. This cell line has a glycosylation defect, which can be reversed by addition of different monosaccharides to the cell culture and enables the production of cells expressing the MUC1-Tn glycoforms. After validation with glycospecific antibodies, the CHO-ldlD MUC1 system was used to detect serum MUC1 and MUC1-Tn antibodies. Using this system, we could confirm the presence of MUC1-Tn antibodies in the serum of a patient vaccinated with a truncated MUC1 peptide. This indicates that the CHO-ldlD MUC1 system represents a flow cytometry-based technique to detect antibodies binding to the underglycosylated MUC1 protein. This cellular system is complementary to the previously published methods to detect MUC1 serum antibodies, since the antibodies to the native protein are evaluated and therefore it can be effectively used for MUC1 antibody monitoring in vaccination studies as well as for functional assays.