Immunophenotyping by flow-cyotmetry in MDS and its potential role in remission assessment post treatment

Abstract

18008 Background: Myelodysplastic syndromes (MDS) are a heterogeneous group of myeloid neoplasms with abnormal maturation and differentiation of one or more cell lineages. Diagnosis is complex and attained by evaluation of peripheral blood, bone marrow biopsy and cytogenetics/FISH. Immunophenotyping (IP) has recently been recommended as a co-criterion for diagnosis in a recent consensus publication by Valent et al. Its role in remission assessment is yet to be defined. Our aim was to evaluate the role of IP in a prospective MDS cohort treated with lenalidomide and stem cell factor and correlate morphological response with a modified MDS flow-cytometric scoring system by Wells et al. This scoring system encompasses aberrancy of myelomonocytic populations ranging from 0 in normals to 8 if multiple myelomonocytic aberrancy is determined. Methods: Four colour flow-cytometric analysis was performed to assess blast, granulocytic and monocytic populations. Antibody combinations were compared against isotype controls. Patterns of antibody expression were assessed on marrow samples from 5 normal volunteer donors and 16 haematology patients with a normal peripheral blood and bone marrow evaluation. Sequential assessment was performed using Cheson 2006 morphologic response criteria and modified MDS flow-cytometric scoring system. Results: Normal volunteers included 3 males, median age 27 (range 25–43). The haematology cohort included 16 lymphoma patients, median age 46 (range 19–79). 8 MDS patients were evaluable, median age 57 (range 43–89), including 6 males. MDS WHO subtypes included 3 cases 5q- syndrome, 2 RCMD ± (RS), 2 MDS-U, 1 RAEB type I. 5q- syndrome patients had isolated karyotypic anomalies, 5 patients had a normal karyotype. MDS flow scores pretreatment ranged from 3–5. Of the 6 patients who responded (4 CR, 2 PR) 4 demonstrated substantial improvement in their MDS flow scores with one attaining a normal score. 1 patient did not have sequential immunophenotyping after early withdrawal from the trial. Conclusions: This early cohort demonstrates potential utility of the MDS scoring system not only as a diagnostic tool but in post treatment response assessment. Larger numbers of patients are required in a prospective setting for confirmation of these findings. No significant financial relationships to disclose.