Proportion of U.S. Trends in Breast Cancer Incidence Attributable to Long-term Changes in Risk Factor Distributions
A partir des données des registres américains des cancers, cette étude analyse la part des différents facteurs de risque dans l'incidence du cancer du sein (notamment l'indice de masse corporelle, l'âge lors des premières règles, le nombre de naissances, l'âge à la première naissance) sur la période 1980-2008
Background: U.S. breast cancer incidence has been changing, as have distributions of risk factors, including body mass index (BMI), age-at-menarche, age-at-first-live-birth and number of live births. Methods: Using data for U.S. women from large nationally representative surveys, we estimated risk factor distributions from 1980-2008. To estimate ecologic associations with breast cancer incidence, we fitted Poisson models to age- and calendar-year-specific incidence data from the National Cancer Institute's Surveillance, Epidemiology and End Results registries from 1980-2011. We then assessed the proportion of incidence attributable to specific risk factors by comparing incidence from models that only included age and calendar period as predictors with models that additionally included age- and cohort-specific categorized mean risk factors. Analyses were stratified by age and race. Results: Ecologic associations usually agreed with previous findings from analytic epidemiology. From 1980-2011, compared to the risk factor reference level, increased BMI was associated with 7.6% decreased incidence in women aged 40-44 and 2.6% increased incidence for women aged 55-59. Fewer births were associated with 22.2% and 3.99% increased incidence in women aged 40-44 and 55-59 years, respectively. Changes in age at menarche and age-at-first-live-birth in parous women did not significantly impact population incidence from 1980-2011. Conclusions: Changes in BMI and number of births since 1980 significantly impacted U.S. breast cancer incidence. Impact: Understanding and quantifying long-term impact of risk factor trends on incidence is important to understand the future breast cancer burden and inform prevention efforts.