Myeloproliferative neoplasms in the young: Mayo Clinic experience with 361 patients age 40 years or younger

Abstract Between 1967 and 2017, 361 patients with myeloproliferative neoplasms (MPN), age ≤ 40 years, were seen at our institution, constituting 12% of all MPN patients ( n = 3023) seen during the same time period; disease‐specific incidences were 12% in polycythemia vera (PV; n = 79), 20% in essential thrombocythemia (ET; n = 219) and 5% in primary myelofibrosis (PMF; n = 63). Compared to their older counterparts, younger patients were more likely to present with low risk disease ( P < .001) and display female preponderance in ET ( P = .04), lower incidence of arterial events overall ( P < .001), and higher incidence of venous thrombosis in PV ( P = .01). Younger patients were also more likely to express CALR mutations, in ET and PMF, normal karyotype, in PV and PMF, and lower incidence of high molecular risk mutations in PMF ( P significant in all instances ). Over median follow‐up of 11.3, 13, and 7.1 years for PV, ET, and PMF, leukemic transformations were respectively documented in 4%, 2%, and 10% ( P values 0.1‐0.9) while incidences of fibrotic progression in PV (22%) and ET (16%) were expectedly higher in young patients, because of their longer survival ( P < .001). Median survival in young patients was 37 years for PV, 35 for ET and 20 for PMF; the corresponding values were 22, 22, and 8 years for ages 41‐60 years and 10, 11, and 3 years for ages >60 years ( P < .001). Young MPN patients comprise a unique disease subset defined by an attenuated‐risk cytogenetic and mutational backdrop and conspicuously longer survival compared to their older counterparts, which requires assertion during patient counseling.