Prognostic value of flow cytometry in myelodysplastic neoplasms (MDS): Composition of a FCM‐prognostic score (FCM‐PS) for overall survival

Flow cytometry (FCM) is a co‐criterion in myelodysplastic neoplasms (MDS) diagnostics, currently not used for prognostication. This study aimed to develop an FCM‐score predicting overall survival (OS) in MDS to improve early clinical patient prognostication. FCM of bone marrow samples was performed for diagnostic purposes in 509 therapy‐naïve MDS patients and 77 healthy donors. The following methodology was used: (1) uni‐ and multivariate Cox proportional hazards regression and Kaplan–Meier curves for OS to assess FCM‐parameters' prognostic value; (2) receiver operating characteristic (ROC) curves to test the prognostic superiority of FCM‐parameters versus established FCM‐scores and clinical risk‐scores; and (3) development of a FCM‐prognostic score (FCM‐PS) based on six FCM‐parameters with independent prognostic impact. The final FCM‐PS included aberrancies of progenitor cells (increased CD45 mean fluorescence intensity [MFI]‐ratio of lymphocytes and myeloid progenitor cells, decreased % of lymphatic progenitor cells), granulopoiesis (increased CD33 MFI, decreased sideward scatter [SSC]‐ratio of granulopoiesis and lymphocytes), lymphocytes (increased % of B‐lymphocytes), and plasmacytoid dendritic cells (increased %). FCM‐PS outperformed established scores for OS (hazard ratio [HR] 4.08 [95% CI 2.54−6.55] vs. Ogata‐score: 2.44 [1.61−3.70], International Prognostic Scoring System‐Revised [IPSS‐R]: 2.37 [1.61–3.49], International Prognostic Scoring System‐Molecular [IPSS‐M]: 0.816 [0.303–2.196]). Patients in the FCM‐PS low score category showed significantly better OS (P < 0.0001). Further, FCM‐PS allowed discrimination within IPSS‐R area under the curve [AUC]: 0.70 vs. 0.62) and IPSS‐M (AUC: 0.75 vs. 0.48) subgroups. Validation of the prognostic FCM‐PS in an independent patient cohort confirmed good discrimination performance (AUC: 0.70). We introduce a unique, easy‐to‐use prognostic FCM‐PS score (panel: CD45/CD34/CD117/CD33/CD19/CD123/HLA‐DR) for OS in MDS, allowing refined risk stratification for IPSS‐R subgroups.