title: Preventable breast cancer is postmenopausal.
abstract: Breast cancer incidence has markedly increased in Western countries for reasons that are not entirely understood. We characterized periodic and age-specific incidence trends of breast cancer in immigrants who migrated from low incidence areas to Sweden. The incidence in immigrants was compared to that in native Swedes and standardized incidence ratios (SIRs) were calculated, based on the Swedish Family-Cancer Database. Age-specific incidence data for low and high incidence populations were obtained from Cancer Incidence in Five Continents IX and NORDCAN. For immigrants from the seven lowest countries/regions 535 breast cancers were identified; the SIRs ranging from 0.45 for Turkish to 0.70 for Greek women. The SIR increased somewhat with the length of stay in Sweden, from 0.55 for stay between 0 and 10 years to 0.59 for a stay of 20+ years. The age-specific incidence curves for these immigrants were superimposable upon the earliest Swedish (year 1960) or Danish (1943) rates. These rates differed from the current Swedish rates by a much lower postmenopausal component. Large incidence differences were also observed between white Californians and immigrants from China and Korea. Our results show that the main difference between high and low incidence areas is in postmenopausal cancer which has increased preferentially during the past century. Immigrants from low risk areas to Sweden show age-specific incidence patterns of Swedes half a century ago. These differences offer opportunities for the identification of factors underlying breast cancer etiology and tools for prevention.
authors.affiliation: Division of Molecular Genetic Epidemiology, German Cancer Research Centre (DKFZ), 69120 Heidelberg, Germany. k.hemminki@dkfz.de
authors.forename: Kari
authors.initials: K
authors.lastname: Hemminki
authors.forename: Asta
authors.initials: A
authors.lastname: Försti
authors.forename: Jan
authors.initials: J
authors.lastname: Sundquist
authors.forename: Seyed Mohsen
authors.initials: SM
authors.lastname: Mousavi
mesh_terms: D000328:Adult; D017677:Age Distribution; D000367:Age Factors; D000368:Aged; D044466:Asian People / Q000706:statistics & numerical data*; D001943:Breast Neoplasms / Q000208:ethnology* / Q000517:prevention & control*; D019992:Databases as Topic; D054242:Emigrants and Immigrants / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D017698:Postmenopause; D018570:Risk Assessment; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology; D013997:Time Factors; D044465:White People / Q000706:statistics & numerical data*; D055815:Young Adult