June 26, 2024
The classical BCR:: ABL1-negative myeloproliferative neoplasms (Ph- MPNs) polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) are typically diseases of older adults, with a median age at diagnosis within the sixth decade of life. In two large case series from cancer centers in the United States, adolescent and young adult (AYA) patients were reported to account for 11 to 12% of the Ph- MPNs evaluated.1,2 The data on AYA patients with Ph- MPNs is less robust than that available for their older counterparts, and this patient population may not be represented in cohorts used to develop prognostic scoring systems.
Recently, James T. England, MD, MSc, and colleagues investigated the clinical features and long-term outcomes of a cohort of 609 patients (17 pediatric patients aged <18 years and 592 patients aged 18-45 years) with Ph- MPNs from across eight participating centers in Canada. Initial diagnoses are shown in Figure 1. Clinical features from the current study cohort are compared with those of a 2018 Mayo Clinic AYA cohort1 (Table). The patients were diagnosed between 2000 and 2022, with MPN driver mutation analysis performed in 89% and next-generation sequencing (NGS) of clinically relevant myeloid genes performed in 48%. More than one-third of patients (211) had NGS testing first performed during initial disease phase, with a median time from diagnosis of 3.9 years (range, 0-29 years). Sixty-four patients had NGS first performed during the post-ET/post-PV secondary myelofibrosis (SMF) phase, while 19 had NGS first performed during the accelerated phase (AP)/blast phase (BP) of disease. Non-MPN driver mutations were detected in a higher proportion of patients evaluated during disease progression (secondary myelofibrosis or elevated blasts) than during initial disease phase, including more frequent high molecular risk (HMR) mutations (Figure 2). Mutations defined as HMR included pathogenic and likely pathogenic variants in ASXL1, EZH2, IDH1/2, SRSF2, TP53, and U2AF1Q157. Among those patients with NGS testing performed during the initial disease phase, additional mutations were most frequently detected in those with overt PMF (26%).