Email updates

Keep up to date with the latest news and content from BMC Cancer and BioMed Central.

Open Access Highly Accessed Research article

Higher incidence of premenopausal breast cancer in less developed countries; myth or truth?

Reza Ghiasvand12, Hans-Olov Adami34, Iraj Harirchi1, Rahim Akrami15 and Kazem Zendehdel14*

Author Affiliations

1 Cancer Research Center, Cancer Institute of Iran, Tehran University of Medical Sciences, Tehran, Iran

2 Department of Biostatistics, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway

3 Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA

4 Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden

5 Sabzevar University of Medical Sciences, Sabzevar, Iran

For all author emails, please log on.

BMC Cancer 2014, 14:343  doi:10.1186/1471-2407-14-343

Published: 19 May 2014

Abstract

Background

Fundamental etiologic differences have been suggested to cause earlier onset of breast cancer in less developed countries (LDCs) than in more developed countries (MDCs). We explored this hypothesis using world-wide breast cancer incidence data.

Methods

We compared international age-standardized incidence rates (ASR) of pre- (<50 years) and postmenopausal (≥50 years) breast cancers as well as temporal trends in ASRs of pre-and postmenopausal breast cancer among selected countries during 1975–2008. We used joinpoint log-linear regression analysis to estimate annual percent changes (APC) for premenopausal and postmenopausal breast cancer in the northern Europe and in Black and White women population in the US.

Results

Premenopausal breast cancers comprised a substantially higher proportion of all incident breast cancers in LDCs (average 47.3%) compared to MDCs (average 18.5%). However, the ASR of premenopausal breast cancer was consistently higher in MDCs (29.4/100,000) than LDCs (12.8/100,000). The ASR of postmenopausal cancer was about five-fold higher in the MDCs (307.6/100,000) than the LDCs (65.4/100,000). The APC of breast cancer in Denmark was substantially higher in postmenopausal (1.33%) than premenopausal cancer (0.98%). Higher incidence of breast cancer among the white than black women in the US was pertained only to the postmenopausal cancer.

Conclusion

The substantial and consistent lower age-specific incidence of breast cancer in LDCs than in MDCs contradicts the theory of earlier onset. Demographic differences with fewer old women in LDCs and lower prevalence of risk factors of postmenopausal cancer are the most likely explanation to the lower mean age at diagnosis in these countries.

Keywords:
Breast cancer; Age-standardized rate; Risk factor; Annual percent change; Less developed countries; Premenopausal