Incidence of myeloproliferative neoplasms – trends by subgroup and age in a population-based study in Sweden

Background: The reported incidence of Philadelphia-negative myeloproliferative neoplasms (MPNs) differs substantially between previous reports, likely due to true regional differences in incidence and/or variations in the quality and coverage of the cancer registers. Objective: We therefore assessed MPN incidence in Sweden during recent years using prospectively collected information captured in Swedish health registers. Methods: Patients with MPNs were identified through the Swedish Cancer Register and Swedish Blood Cancer Register between 2000 and 2014. Information on the Swedish population was obtained from the Human Mortality Database. Crude and age-standardized incidence rates of MPNs with 95% confidence intervals (CIs) were calculated. Results: A total of 6281 MPN cases were reported to the Swedish Cancer Register and Swedish Blood Cancer Register during 2000–2014. The age-standardized, to the Swedish population in 2000, incidence for all MPNs was 4.45 (95% confidence interval [CI] 4.34–4.56)/100 000 person-years. The age-standardized incidence for polycythemia vera was 1.48 (1.42–1.54), for essential thrombocythemia 1.60 (1.53–1.66) and for primary myelofibrosis 0.52 (0.48–0.56)/100 000 person-years, respectively. The incidence rate of MPNs was substantially higher in the older compared to the younger age groups. The incidence increased during the study period, likely to do better reporting and increasing age of the general population. Conclusion: The reported MPN incidences in our study, which were in the higher interval of previously published studies, are likely more accurate compared to previous reports due to the population-based setting and high level of coverage in the Swedish Cancer and Blood Cancer Registers.