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Childhood and adolescent leukaemia in a North American population
1Department of Community Health and Epidemiology, University of Saskatchewan, Saskatoon, Canada.
Objective:
This was to describe and analyse incidence and survival data on childhood leukaemias.
Sample:
Incident leukaemia cases aged 0-19 from the cancer registry holdings of the province of Saskatchewan for the 60-year period 1932-1991 are the subject of this descriptive report.
Methods:
Age-adjusted, age-specific, histologic-type specific, sex-specific, and cohort-specific incidence trends were reviewed. Univariate and multivariate survival analyses explored the effects of time period, age at diagnosis, gender, and histologic type.
Results:
Acute lymphocytic leukaemia (ALL) occurred more commonly in males and before the age of five; the 1982-1991 age-adjusted incidence is 3.1/100,000. Increasing incidence has been consistently noted, but has attenuated since 1971. The relative risk of developing ALL in the first 9 years of life, using children born from 1944 to 1948 as baseline, increased with each successive 5-year birth cohort until 1969-1973; since then the risk has been stable. Other histologic types were rare; over 60 years there were only 85 cases that could be grouped as acute non-lymphocytic leukaemias (ANLL); the 1982-1991 age-adjusted ANLL incidence is 0.6/100,000. A dramatic improvement in survival was seen over the last six decades, primarily for ALL. In ALL, children under five have better survival than older children and adolescents; the reverse is true for ANLL.
Conclusions:
ALL and ANLL are distinctive diseases clinically and the epidemiological findings are likewise distinctive. Our current ALL patterns are consonant with a number of other published reports. However, our small numbers of ANLL limit inferences.