Have diagnostic practices contributed to trends in leukemia incidence and mortality among Canadians?

Abstract

Objective: To outline the patterns and temporal trends in leukemia, regarding incidence and mortality, in Canada since 1970.

Design: A descriptive analysis of trends in incidence and mortality by age, sex, time period and leukemia subtype, using change-point modelling and log-linear regression.

Setting: Data from all provincial and territorial cancer registries.

Main outcome measure: Incidence and mortality rate per population of 100,000.

Results: The overall age-adjusted incidence rates for all males and females increased from 12.3 and 7.3 per 100,000 in 1970-1972 to 14.6 and 9.0 in 1979-1981, then decreased to 13.2 and 8.3 in 1991-1993, respectively. The overall age-adjusted mortality rates decreased from 9.1 and 5.7 per population of 100,000 in 1970-1972 to 8.3 and 4.8 in 1993-1995 for males and females, respectively. The incidence of acute leukemias decreased between 1970 and 1993. A sharp increase in the incidence of chronic leukemias from 1978 to 1980 was observed in the older age group. Mortality rates also showed a small increase from 1979 to 1989 in seniors.

Conclusion: The increase in the incidence of chronic leukemias among older subjects was probably due to improvements in diagnosis and changes in registration practices, whereas the decrease in the incidence of acute leukemias was probably a real change attributable to environmental factors. Further investigation is needed to clarify whether and to what extent diagnostic practices contributed to the increased detection of chronic leukemias among elderly Canadians.