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Does the breast cancer age at diagnosis differ by ethnicity? A study on immigrant to Sweden

Author(s): Kari Hemminki | Seyed Mohsen Mousavi | Jan Sundquist | Andreas Brandt

Journal: Iranian Journal of Nuclear Medicine
ISSN 1681-2824

Volume: 18;
Issue: Suppl 1;
Start page: 128;
Date: 2010;
Original page

Keywords: Ethnic-differences | Age-incidence | Risk factors | Environmental effect

Introduction: Age-specific incidence rates for breast cancer in low-risk and high-risk ethnic populations differ by age at which the incidence maximum is reached: around 50 years in low-risk populations and over 60 years in high-risk populations. The interpretation of these differences has been controversial, one line referring to biological differences, second one to cohort effects of rapidly increasing rates in young populations and third one to incomplete registration of cancer in the old. Methods: The nation-wide Family-Cancer Database was used to analyze standardized incidence ratios (SIRs) and age at diagnosis of breast cancer in female immigrants to Sweden by their region of origin compared to Swedish women matched on birth year and other relevant factors. Results: We showed first that the SIRs for breast cancer were lower in many immigrant groups compared to Swedes; Turkish women had the lowest SIR of 0.45, followed by Chileans (0.54) and Southeast Asians (0.57). Women from nine regions showed an earlier mean age at diagnosis than their matched Swedish controls, the largest differences being 5.5 years for Turkish, 5.1 years for Asian Arab and other African, 4.3 years for Iranian and 4.0 years for Iraqi women. Conclusion: The results show that in many immigrant groups the diagnostic age is earlier than in Swedes, suggesting that biological factors underlie the differences. These factors are mainly related to postmenopausal breast cancer and they should explain much of the international variation in breast cancer incidence. Identifying these factors should advance understanding on breast cancer etiology and prevention.
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