Serial Assessment of Patients with Suspected Myelodysplastic Syndromes: Significance of Flow Cytometric Findings As Validated by Cytomorphology, Cytogenetics, and Molecular Genetics

Multiparameter flow cytometry (MFC) is capable of detecting aberrant antigen expression related to myelodysplastic syndromes (MDS) and is increasingly applied as a diagnostic tool in patients with cytopenias and suspected MDS. While in the majority of cases concordant diagnostic results between MFC and cytomorphology (CM) are found, the significance of MFC indicating MDS in the absence of a diagnosis of MDS by CM remains to be clarified. Aim: To assess the course of disease in serially analyzed patients with suspected MDS in whom the first evaluation revealed MDS by MFC but not by CM. Patients and Methods: A total of 142 patients were analyzed in parallel by MFC, CM and cytogenetics (CG) for suspected MDS on at least two separate occasions. The median number of assessments amounted to 2 (range 2–6). The median interval between first and last assessment amounted to 9 months (range 1–53). In a subset of the assessments molecular genetic (MG) analyses were performed for the detection of RUNX1 mutations and FLT3-ITD. Results: At the first assessment MFC results indicated MDS in 64/142 (45.1%) patients and revealed no sign of MDS in 33/142 (23.2%) patients. In the remaining 45/142 (31.7%) patients only minor aberrancies of antigen expression were observed by MFC not sufficient to indicate MDS (“possible MDS by MFC”). In 9/142 (6.3%) patients CG revealed an aberrant karyotype and thereby confirmed MDS at the initial assessment. This applied to 1/33 (3.0%) patient with no MDS by MFC, 3/45 (6.7%) patients with possible MDS by MFC, and 5/64 (7.8%) with MDS by MFC (n.s.). Karyotype abnormalities included complex karyotype (n=3), trisomy 8 (n=1), trisomy 21 (n=1), and others (n=4). These proven MDS patients were excluded from further analyses which were thus based on n=133 patients. During follow-up assessments MDS was confirmed by CM, CG or MG in 30/59 (63.8%) patients with MDS by MFC at initial assessment, in 10/42 (21.3%) with “possible MDS” by MFC at initial assessment, and in 7/32 (14.9%) with no MDS by MFC at initial assessment (p=0.004). The respective median intervals between initial assessment and confirmation of MDS by a non-MFC method amounted to 10.8 months (range, 1.7–53.1), 10.3 months (range, 2.4–36.9), and 15.6 months (range, 7.9–44.4). Thus, in a total of 47 patients follow-up assessments revealed MDS by non-MFC methods as follows: n=38 by CM (36 MDS, 2 AML), n=8 by CG (one case each with del(5q), del(11q), del(20q), trisomy 8, and trisomy 4 and three cases other abnormalities) and n=4 by MG (2 RUNX1 mutations, 1 RUNX1 mutation and FLT3-ITD, 1 FLT3-ITD). Notably, in the 7 patients with no MDS by MFC at the initial assessment, in whom follow-up assessments revealed MDS by non-MFC methods, changes in MFC results at follow-up assessments to “possible MDS” (n=4) and MDS (n=2) were observed. The respective figure for the 10 patients with “possible MDS” by MFC at initial assessment, who were confirmed MDS by non-MFC methods during follow-up assessments, is “possible MDS” in 5 patients and MDS in 4 patients during follow-up MFC assessment. Conclusions: This data indicates that diagnostic findings by MFC revealing MDS in the absence of diagnostic findings of MDS by CM are confirmed in the majority of cases during follow-up. Furthermore, the confirmation of MDS during follow-up even in cases with minor aberrancies of antigen expression is higher as compared to cases with no MDS by MFC. There remains, however, a significant number of patients (36.2%) with MDS by MFC which is not confirmed by other methods during follow-up; further clinical evaluation is needed to validate the significance of MFC findings in these cases. Overall, this data argues in favour of a combined approach to diagnose MDS including MFC besides CM, CG and MG, and suggests a closer monitoring of patients with suspected MDS in whom aberrancies are detected by MFC.

Kern:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Schnittger:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Alpermann:MLL Munich Leukemia Laboratory: Employment. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.