Resurgence of myeloproliferative neoplasm in patients in remission from blast transformation after treatment with hypomethylating agents.

Subsequent blast (BP) or accelerated phase (AP) is a severe complication of Philadelphia-negative myeloproliferative neoplasms (MPNs). The prognosis is generally dismal, but hypomethylating agents (HMAs) may induce a long-lasting response in a minority of patients. Here, we report a cohort of six patients with BP/AP-MPN who experienced MPN relapse after a leukemia response was obtained with azacytidine. Five of the patients achieved complete remission despite the presence of characteristics associated with poor prognosis, such as complex and monosomal karyotypes, TP53 mutations, and EVI1 overexpression. These remissions persisted for over five years in four of the 6 patients. All patients showed rapid reemergence of MPN within a median of two months with thrombocytosis requiring the addition of anagrelide, hydroxyurea, or ruxolitinib given continuously in parallel with the azacytidine cycle. Serial JAK2 V617F allelic burden measurements showed little variation. Thromboembolic events occurred in 3 patients, one leading to death. These findings confirm that HMA may reverse the disease course in AP/BP-MPN to a more chronic phase that may last for years but also lead to morbidity and mortality. Combining maintenance therapy with HMA and MPN-specific drugs appears to be a possible approach to avoiding leukemia relapse and controlling MPN disease.