Myeloproliferative neoplasms: trends in incidence, prevalence and survival in Norway.

BACKGROUND: Polycythemia vera (PV), essential thrombocythemia (ET) and myelofibrosis (MF) are clonal disorders collectively named as myeloproliferative neoplasms (MPN). Published data on epidemiology of MPN after the discovery of the JAK2 mutation and the 2008 WHO classifications are scarce. We aimed to study the incidence rates, prevalence and survival of MPN in Norway during the period 1993-2012.

METHOD: We identified 2453 persons diagnosed with MPN from the Cancer Registry of Norway between 1993 and 2012. We report age-adjusted incidence rates, prevalence, relative survival and standardised mortality rates.

RESULTS: The overall age-adjusted yearly incidence rate of PV increased from 0.4/10⁵ to 0.7/10⁵, ET increased from 0.3/10⁵ to 1.0/10⁵ and MF from 0.2/10⁵ to 0.5/10⁵. Prevalence of PV, ET and MF was 9.2, 8.6 and 3.0 per 10⁵ inhabitants, respectively. The five-year relative survival (RS) of ET and PV was slightly reduced with no improvement. The five-year RS of MF was 58.1% (2008-2012). Standardised mortality rate (SMR) was 1.9 (95% CI 1.2 - 2.7).

CONCLUSIONS: The incidence rates of ET, PV and MF doubled and tripled during the years 2007-2012 as compared to 1995-2006. This increment in incidence rates may be related to identification of the JAK2 mutation and the derived 2008 WHO guidelines for MPN. The RS was only slightly reduced in PV and ET, but was substantially reduced in MF.