[Breast cancer--incidence, mortality and stage shifting in Norway].
The age-standardized incidence rate of breast cancer has increased by 50% over the period 1965-94. There has been a much lesser increase in the corresponding age-standardized mortality rate because of better treatment and stage shifting. Stage shifting means that the proportion of individuals with a given clinical stage changes over time. The proportion of individuals diagnosed as clinical stage 1 was seen to increase from about 50% to 60% in the time period mentioned above. The proportion classified as stage 2 at the time of diagnosis is constant at 30%. The relative numbers of individuals diagnosed as stage 3 or 4 were reduced from 10% to 3% and from 10% to 5%, respectively. After correction for confounding effect of age and the clinical stage, the age-standardized 3-year relative survival rate increased from 90% to 95% and from 67% to 85% for stages 1 and 2, respectively. The impact of advancing breast cancer diagnosis independent of the screening programme, is discussed. Finally, the evaluation of screening programmes using shift migration models and simulations is discussed.
Zahl
P H
PH
Department of Biostatistics, University of Washington, Seattle 98195, USA.
D000328:Adult; D000367:Age Factors; D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000401:mortality / Q000473:pathology; D005260:Female; D006801:Humans; D015994:Incidence; D008403:Mass Screening; D008875:Middle Aged; D009367:Neoplasm Staging; D009664:Norway / Q000453:epidemiology