Minimal residual disease (MRD) assessment is standard in many hematologic malignancies but is considered investigational in multiple myeloma (MM). We report a prospective analysis of the prognostic importance of MRD detection by multiparameter flow cytometry (MFC) in 295 newly diagnosed MM patients uniformly treated in the GEM2000 protocol VBMCP/VBAD induction plus autologous stem cell transplantation [ASCT]). MRD status by MFC was determined at day 100after ASCT. Progression-free survival (PFS; median 71 vs 37 months, P < .001) and overall survival (OS; median not reached vs 89 months, P ؍ .002) were longer in patients who were MRD negative versus MRD positive at day 100 after ASCT. Similar prognostic differentiation was seen in 147 patients who achieved immunofixation-negative complete response after ASCT. Moreover, MRD ؊ immunofixation-negative (IFx ؊ ) patients and MRD ؊ IFx ؉ patients had significantly longer PFS than MRD ؉ IFx ؊ patients. Multivariate analysis identified MRD status by MFC at day 100 after ASCT as the most important independent prognostic factor for PFS (HR ؍ 3.64, P ؍ . IntroductionIn most hematologic malignancies, response to front-line therapy is a good predictor of prognosis, with the longest survival seen in patients achieving an optimal response. This paradigm is represented by chronic myeloid leukemia (CML), in which hematologic, cytogenetic, and molecular remissions define progressively better response to therapy. In consequence, investigations to define these levels of remission are mandatory in routine clinical practice for treatment stratification and assessment of prognosis. 1 The situation is similar for other malignancies such as acute promyelocytic leukemia (APL) or acute lymphoblastic leukemia (ALL). 2,3 For this reason, there are continuous efforts to improve the sensitivity of the methods used to assess response to therapy, mainly through the introduction and refinement of both molecular and immunophenotyping approaches, as well as imaging techniques.Multiple myeloma (MM) should be no exception to this paradigm. For many years, the major goal of MM therapy was to achieve partial response (PR) or disease stabilization. 4,5 With the introduction of high-dose therapy plus autologous stem cell transplantation (HDT/ASCT), the new goal became the achievement of complete response (CR), defined as absence of M-protein by immunofixation (IFx) and less than 5% plasma cells (PCs) in bone marrow (BM). 6,7 More recently, the International Myeloma Working Group proposed a new response category of "stringent CR," which requires normalization of the free light chain ratio and the absence of residual clonal cells in the BM by immunohistochemistry or immunofluorescence. 8 As noted previously, the assessment of minimal residual disease (MRD), residual tumor cells persisting after therapy, is part of the standard of care in many hematologic malignancies, whereas in MM this is still considered investigational. Thus, MRD studies in MM have involved mainly small series of patients or have...
Leukemic B-chronic lymphoproliferative disorders (B-CLPDs) are generally believed to derive from a monoclonal B cell; biclonality has only occasionally been reported. In this study, we have explored the incidence of B-CLPD cases with 2 or more B-cell clones and established both the phenotypic differences between the coexisting clones and the clinicobiologic features of these patients. In total, 53 B-CLPD cases with 2 or more B-cell clones were studied. Presence of 2 or more Bcell clones was suspected by immunophenotype and confirmed by molecular/ genetic techniques in leukemic samples (n ؍ 42) and purified B-cell subpopulations (n ؍ 10). Overall, 4.8% of 477 consecutive B-CLPDs had 2 or more B-cell clones, their incidence being especially higher among hairy cell leukemia (3 of 13), large cell lymphoma (2 of 10), and atypical chronic lymphocytic leukemia (CLL) (4 of 29). In most cases the 2 B-cell subsets displayed either different surface immunoglobulin (sIg) light chain (n ؍ 37 of 53) or different levels of the same sIg (n ؍ 9 of 53), usually associated with other phenotypic differences. Compared with monoclonal cases, B-CLL patients with 2 or more clones had lower white blood cell (WBC) and lymphocyte counts, more frequently displayed splenomegaly, and required early treatment. Among these, the cases in which a CLL clone coexisted with a non-CLL clone were older and more often displayed B symptoms, a monoclonal component, and diffuse infiltration of bone marrow and required early treatment more frequently than cases with monoclonal CLL or 2 CLL clones. (Blood. 2003;102:2994-3002)
Multiparameter immunophenotypic analysis of neoplastic cells has proven to be of great help for the investigation of minimal residual disease in acute leukemias; however, its utility has not been systematically explored in B cell chronic lymphoproliferative disorders. The aim of the present study was to investigate the incidence of phenotypic aberrations in a series of 467 consecutive leukemic B cell chronic lymphoproliferative disorders through the comparison of the phenotypic characteristics of tumor vs normal peripheral blood (n = 10) and bone marrow (n = 10) B cells, in order to explore the applicability of this strategy for minimal residual disease monitoring. An additional goal of our study was to evaluate the sensitivity of multiparameter flow cytometry for the detection of minimal residual disease in leukemic B cell chronic lymphoproliferative disorders through dilutional experiments (n = 19). From the patients analyzed 382 corresponded to B cell chronic lymphocytic leukemia/small lymphocytic lymphoma (353 typical and 29 atypical); five to prolymphocytic leukemia; 13 to hairy cell leukemias; 12 to lymphoplasmacytic lymphomas; 14 to splenic marginal zone lymphomas; 22 were follicular lymphomas; and 19 mantle cell lymphomas. The following triple stainings were systematically applied to both normal and leukemic samples: FMC7/CD5/CD19, CD22/CD23/CD19, CD103/CD25/CD19, CD10/CD11c/CD19 and sIg/sIg /CD19. Overall, 98% of the leukemic B cell chronic lymphoproliferative disorders cases displayed aberrant phenotypes at diagnosis with no significant differences being found between cases analyzed in peripheral blood vs bone marrow samples. The most common types of aberrant criteria detected included asynchronous antigen expression (92%) and antigen over-expression (54%); abnormally light scatter characteristics were found in 17% of the cases. Most of the cases studied (90%) displayed four or more phenotypic aberrations. Once patients were divided according to the different diagnostic subgroups, the overall incidence of aberrant phenotypes ranged from 79 to 80% among atypical B cell chronic lymphocytic leukemia/small lymphocytic lymphoma and prolymphocytic leukemia to 97% of follicular lymphoma and 100% of typical B cell chronic lymphocytic leukemia/small lymphocytic lymphoma, hairy cell leukemia, lymphoplasmacytic lymphomas, splenic marginal zone lymphomas and mantle cell lymphomas. Based on the aberrant phenotypes detected unique four-color stainings could be built for the specific identification of aberrant phenotypes. These include CD22/CD23/CD19/CD5 and sIg /sIg /CD19/CD5 for lymphocytic leukemia/small lymphocytic lymphoma and prolymphocytic leukemia, CD103/CD25 or CD22/CD19/CD11c for hairy cell leukemia, FMC7/CD22/CD19/CD103 and sIg /sIg /CD22/CD19 for splenic marginal zone lymphomas, CD22/CD23/CD19/CD10 for follicular lymphomas and CD10/CD22/CD19/CD5 for mantle cell lymphomas. Serial dilutional experiments showed that the sensitivity level of immunophenotyping ranges between 10 −4 and 10 −5 . In summary, the p...
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