Prognostic value of blasts in peripheral blood in myelofibrosis in the ruxolitinib era

BACKGROUND: Circulating blasts (peripheral blood PB blasts) ≥1% have long been considered an unfavorable feature for patients with primary myelofibrosis. Whether further quantification of PB blasts and their correlation with bone marrow (BM) blasts have incremental value with regard to patient prognostication is unclear. Similarly, the role of the JAK1/JAK2 inhibitor ruxolitinib (RUX) is not well defined in patients who have increased blasts. METHODS: The authors retrospectively studied 1316 patients with myelofibrosis who presented at their institution between 1984 and 2018 and had available PB and BM blasts. RESULTS: The PB blast percentage influenced overall survival (OS) only among patients who had BM blasts .05). Forty-four percent of patients received RUX throughout their disease course. All patients who had <10% blasts (PB or BM) and received treatment with RUX had superior OS compared with those who did not receive RUX within the same group. PB blasts ≥4% and BM blasts ≥5% were significant for predicting inferior survival in multivariate analysis. CONCLUSIONS: The current results provide comprehensive insight into the role of peripheral blasts in patients with myelofibrosis and indicates that patients who have PB blasts ≥4% have an unfavorable prognosis. RUX provides a survival benefit to patients who have PB blasts <10%.