Measurable residual disease (MRD; previously termed minimal residual disease) is an independent, postdiagnosis, prognostic indicator in acute myeloid leukemia (AML) that is important for risk stratification and treatment planning, in conjunction with other well-established clinical, cytogenetic, and molecular data assessed at diagnosis. MRD can be evaluated using a variety of multiparameter flow cytometry and molecular protocols, but, to date, these approaches have not been qualitatively or quantitatively standardized, making their use in clinical practice challenging. The objective of this work was to identify key clinical and scientific issues in the measurement and application of MRD in AML, to achieve consensus on these issues, and to provide guidelines for the current and future use of MRD in clinical practice. The work was accomplished over 2 years, during 4 meetings by a specially designated MRD Working Party of the European LeukemiaNet. The group included 24 faculty with expertise in AML hematopathology, molecular diagnostics, clinical trials, and clinical medicine, from 19 institutions in Europe and the United States.

Measurable residual disease (MRD) is an important biomarker in acute myeloid leukemia (AML) that is used for prognostic, predictive, monitoring, and efficacy-response assessments. The European LeukemiaNet (ELN) MRD working party evaluates standardization and harmonization of MRD in an ongoing manner and has updated the 2018 ELN MRD recommendations based on significant developments in the field. New and revised recommendations were established during in-person and online meetings, and a two-stage Delphi poll was conducted to optimize consensus. All recommendations are graded by levels of evidence and agreement. Major changes include technical specifications for next generation sequencing (NGS)-based MRD testing and integrative assessments of MRD irrespective of technology. Other topics include use of MRD as a prognostic and surrogate endpoint for drug testing; selection of the technique, material, and appropriate time points for MRD assessment; and clinical implications of MRD assessment. In addition to technical recommendations for flow- and molecular- MRD analysis, we provide MRD thresholds and define MRD response, and detail how MRD results should be reported and combined if several techniques are used. MRD assessment in AML is complex and clinically relevant, and standardized approaches to application, interpretation, technical conduct, and reporting are of critical importance.

CD49d/␣4-integrin is variably expressed in chronic lymphocytic leukemia (CLL

The inability to undergo apoptosis is a crucial mechanism of multidrug resistance in acute myeloid leukemia (AML), and the analysis of mitochondrial apoptotic proteins may represent a significant prognostic tool to predict outcome. Bcl-2 and Bax oncoproteins were evaluated in 255 de novo AML patients (pts) by flow cytometry using an anti-bcl-2 monoclonal antibody (MoAb) and an anti-bax MoAb. The results were expressed as an index (bax/bcl-2) obtained by dividing bax mean fluorescence intensity (MFI) and bcl-2 MFI. Lower bax/bcl-2 ratio was associated with French-American-British (FAB) M0-M1 classes (P ‫؍‬ .000 01) and CD34 more than 20% (P < .000 01). There were striking inverse correlations between CD34 or CD117 MFI and bax/bcl-2 values (r ‫؍‬ ؊.40, P < .000 001 and r ‫؍‬ ؊.29, P ‫؍‬ .000 002), confirming that immaturity is consistent with this index. Moreover, lower bax/bcl-2 levels were correlated with poor-risk cytogenetics (P ‫؍‬ .0002). A significant higher complete remission (CR) rate was found in pts with higher bax/bcl-2 levels (79% versus 45%; P ‫؍‬ .000 01). Also, both a longer overall survival (OS) and disease-free survival (DFS) were observed in pts with higher bax/bcl-2 levels (P ‫؍‬ .000 01 and ‫؍‬ .019). Noteworthy, bax/bcl-2 levels accurately predicted the clinical response and outcome of pts with normal or unknown cytogenetics. Indeed, within this subset of 147 pts, higher bax/bcl-2 ratio was significantly associated both with a higher CR rate (86% versus 42%; P < .000 01) and a longer OS (P ‫؍‬ .0016). The independent prognostic value of bax/bcl-2 ratio was confirmed in multivariate analysis. Therefore, mitochondrial oncoproteins, such as bcl-2 and bax, represent both sensitive indicators of clinical outcome and potential targets of novel proapoptotic molecules in order to circumvent chemoresistance. (Blood. 2003;

The clinical course of B-cell chronic lymphocytic leukemia (B-CLL) is variable, and novel biologic parameters need to be added to the clinical staging systems to predict an indolent or aggressive outcome. We investigated the 70-kDa zetaassociated protein (ZAP-70), CD38, soluble CD23 (sCD23), and cytogenetics in 289 patients with B-CLL. Both a shorter progression-free survival (PFS) and overall survival (OS) were observed in ZAP-70 ؉ (P < .001), in CD38 ؉ (P < .001) and in sCD23 ؉ patients (P < .001 and P ‫؍‬ .013, respectively). ZAP-70 ؉ CD38 ؉ or ZAP-70 ؉ patients with an unmutated IgV H status showed both a shorter PFS (P < .001) and OS (P < .001 and P < .001, respectively) as compared with ZAP-70 ؊ /CD38 ؊ or ZAP-70 ؊ patients with mutated IgV H genes. Discordant patients showed an intermediate outcome. Note, ZAP-70 ؉ patients even if CD38 ؊ or mutated showed a shorter PFS, whereas ZAP-70 ؊ patients even if CD38 ؉ or unmutated had a longer PFS. Furthermore, ZAP-70 positivity was associated with a shorter PFS both within normal karyotype (P < .001) and within the poor-risk cytogenetic subset (P ‫؍‬ .02).

B-cell chronic lymphocytic leukemia (B-CLL) follows heterogeneous clinical courses, and several biological parameters need to be added to the current clinical staging systems to predict which patients will experience an indolent or an aggressive outcome. This study analyzed CD38 expression by flow cytometry and soluble APO1/Fas (sAPO1/Fas), Bcl-2 (sBcl-2), and CD23 (sCD23) proteins by immunoenzymatic methods to evaluate their effect on the clinical course of 168 unselected B-CLL patients. Intermediate/high risk modified Rai stages were characterized by a higher CD38 ؉ B-cell number (P ‫؍‬ .0002) and higher sCD23 levels (P < .0001). Moreover, CD38 ؉ B-cell percentages were significantly and directly associated both with ␤ 2 -microglobulin and sCD23 concentrations (P < .0001 and P ‫؍‬ .002, respectively). Both a higher tumor burden (lymphadenopathy/splenomegaly) and a lymphocyte doubling time less than 12 months were significantly associated with higher CD38 ؉ percentages (P < .0001 and P ‫؍‬ .0001, respectively). With regard to clinical outcome, progression-free survival was significantly longer (75% versus 37% at 5 years; P ‫؍‬ .00006) in patients with lower CD38 ؉ B-cell percentages. Furthermore, the risk of partial or no response to fludarabine increased with increasing CD38 expression (P ‫؍‬ .003), and a shorter overall survival (50% versus 92% at 8 years; P < .00001) characterized patients with more than 30% CD38 ؉ B-cell number. The predictive value of CD38 expression was maintained among the patients within the Rai intermediate risk group and was confirmed in multivariate analysis. Thus, the percentage of CD38 ؉ B cells appears to be an accurate predictor of clinical outcome and therefore could be used to indicate when more novel chemotherapeutic approaches are needed. , and CD19 and negative for surface CD22 and FMC7. 2 These cells overexpress the Bcl-2 gene product and are resistant to apoptosis; however, examining the relative levels of this antiapoptotic protein has not been particularly helpful in predicting clinical outcome. 3,4 The clinical course of patients with B-CLL can be quite variable, with many patients surviving for prolonged periods without any therapy, whereas others succumb rapidly despite aggressive treatment. 5 Although the 2 major staging systems have provided valuable information in addressing this clinical heterogeneity, 6,7 they have been unable to predict an indolent or aggressive course within the intermediate risk category. For this reason, several parameters such as lymphocyte doubling time (LDT), 8 serum levels of ␤ 2 -microglobulin, 9 soluble CD23 (sCD23), 10 serum thymidine kinase levels, 11 bone marrow histology, 12 and cytogenetic abnormalities 13 have been added to the current staging systems to differentiate prognostic subsets.Despite having several characteristics of naive B cells, such as sequences of V H genes in germline configuration (unmutated), B-CLL cells have been shown to have somatically mutated immunoglobulin variable region genes in at least half of the case...

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Key Points A risk-adapted, MRD-driven transplant strategy is a feasible approach for the treatment of younger adults with AML. Pretransplant MRD positivity should not contraindicate delivery of an allogeneic stem cell transplant.