Population-based age- and sex-specific incidence rates in the 4 main types of leukaemia.

Due to recent developments in clinical haematology, 98.8% of all 1980 cases of leukaemia reported to the Danish Cancer Registry during the 4-year period 1973-76 could be subclassified into the 4 main types of leukaemia. Thus, it has been possible to characterize each of these types more accurately than before regarding age- and sex-specific incidence rates, relative frequency, male/female ratio, and median age at diagnosis. Chronic lymphatic leukaemia constituted 38% and chronic myeloid leukaemia 15% of the cases. These figures are larger and smaller, respectively, than these previously reported. The median age of all cases combined was 67 years, and the median age in cases of acute non-lymphocytic leukaemia was 64 years with 59% of the latter patients more than 60 years of age. In childhood myeloid leukaemia, an early incidence peak, not previously described, was observed before the age of 2 years. Analysis of Danish leukaemia incidence rates from 1943 and onwards shows no increase over 3 decades in patients less than 75 years of age. Thus, the observed increase in incidence from 5866-9942/100 000 during the period studied is limited to the very oldest age groups and is probably due to improved diagnostic efforts.