High molecular risk variants, severe thrombocytopenia and large unstained cells count affect the outcome in primary myelofibrosis.

Apart from the driver mutations, high molecular risk (HMR) variants and other factors have been reported to influence the prognosis of primary myelofibrosis (PMF). The aim of our study was to investigate the impact of laboratory and molecular characteristics at the time of diagnosis (TOD) on the PMF outcome. The study group consisted of 82 patients recruited from three Polish university centers. Among the driver mutations, only CALR type 1 positively influenced the overall survival (OS). The risk of progression to accelerated or blastic disease phase (AP/BP) did not depend on the driver mutation type, but was closely associated with the presence of HMR variants (p = 0.0062). The risk of death (ROD) was higher in patients with HMR variants (OR[95%CI] = 4.33[1.52;12.34], p = 0.0044) and in patients with a platelet count at the TOD between 50-100 G/L (HR[95%CI] = 2.66[1.11;6.35]) and < 50 G/L (HR[95%CI] = 8.44[2.50;28.44]). Median survival time was 7.8, 2.2 and 1.4 years in patients with large unstained cells (LUC) count of [0.0-0.2], (0.2-0.4] and > 0.4 G/L at the TOD, respectively. We found an unexpected, hitherto undescribed, association between LUC count at the TOD and PMF prognosis. Our analysis led to the following conclusions: in PMF patients at the TOD 1) the presence of HMR variants, especially combined, is associated with an increased risk of progression to the AP and BP, and shorter OS, 2) severe thrombocytopenia confers worse prognosis than the moderate one, 3) LUC count is closely related with the disease phase, and associated with the ROD and OS.