Patient characteristics and outcomes in adolescents and young adults with classical Philadelphia chromosome-negative myeloproliferative neoplasms.

Little is known about the outcomes of Philadelphia-negative myeloproliferative neoplasms (MPNs) in adolescents and young adults (AYA). We reviewed all patients with essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF) treated at our institution from 1988 to 2016 who were aged 16 to 39 years (AYA) and described their outcomes in comparison to older MPN population. Of 2206 patients, 185 (8.3%) were identified as AYA: 105 (57%) ET, 43 (23%) PV, and 37 (20%) MF. The median age was 33 years [range, 16-39], and median follow-up time 3 years [range, 0.04-25]. JAK2 allele burdens were significantly lower among AYA JAK2V617F-mutated patients in both PV (p = 0.001) and MF (p = 0.005). Seven percent of MPN AYA patients were diagnosed with a thrombotic event at, or prior to, diagnosis. Over the short median follow-up, 4 thrombotic (PV = 1, MF = 3) and 3 leukemia (ET = 2, MF = 1) events occurred. In multivariate analysis, AYA did not predict for thrombotic or transformational events across three cohorts. In the MF cohort, there was a reduced frequency of negative prognostic variables of anemia (p = 0.011) and leukocytosis (p = 0.048) in AYA when compared with non-AYA. Overall survival was significantly superior in the AYA cohorts in all three MPN groups, namely MF (p < 0.001), PV (p < 0.001), and ET (p = 0.002). Our findings suggest that MPN AYA patients exhibit an indolent clinical phenotype characterized by favorable survival outcomes.