Sequential population-based studies over 25 years on the incidence and survival of acute de novo leukemias in Estonia and in a well-defined region of western Sweden during 1982–2006: a survey of patients aged ≥65 years

Estonia regained independence in 1991 after five decades of occupation by the Soviet Union. The present population-based survey was carried out over five consecutive 5-year study periods (1982–2006) on the incidence and survival of de novo acute leukemia patients aged ≥65 years at diagnosis in Estonia and in a well-defined area in western Sweden. During the study period of retrospective work (1982–1996), the first 10 years were carried out while Estonia was still under the mentorship of the Soviet Union. Over these years, Estonian hematologists did not have access to therapeutic measures readily available to Swedish hematologists, and the results for survival for western Swedish patients with acute myeloid leukemia (AML) far exceeded those of their Estonian counterparts. However, the results for acute lymphoblastic leukemia were equally dismal in the two countries. Subsequent prospective population-based studies were carried out during the years 1997–2006. A gradual improvement as to long-term relative survival of the Estonian AML patients was observed. When studying 2002–2006, no difference as regards relative survival at 5 years was anymore present between the two countries. Over the first 20 years of our population-based studies, it was repeatedly observed that the age-standardized incidence rate particularly for de novo AML was considerably higher for the western Swedish as compared to the Estonian cohorts. During the last 5-year study period (2002–2006), no such difference between the two countries was present, indicating that some true changes in the reporting procedure in Estonia had occurred.