Breast cancer in pre-menopausal women in West Africa: Analysis of temporal trends and evaluation of risk factors associated with reproductive life q Dominique Sighoko a, d , Bakarou Kamaté b , Cheick Traore b , Brahima Mallé b , Bourama Coulibaly b , Agnès Karidiatou b , Coulibaly Diallo b , Ebrima Bah a, c , Valerie McCormack a , Richard Muwonge a , Denis Bourgeois d , Emmanuelle Gormally e , Maria Paula Curado f , Siné Bayo b , Pierre Hainaut a, * a International Agency for Research on Cancer,150 Cours Albert-Thomas, 69372 Lyon Cedex 08, France b Department of Pathological Anatomy and Cytology, University Hospital of Point G, Bamako, Mali c Gambia Hepatitis Intervention Study, Banjul, The Gambia d Laboratory of Sciences Complex Decision and (in) Health Policy, University Lyon 1, Lyon, France e Faculty of Science, Catholic University of Lyon, Lyon, France f International Prevention Research Institute, France article info Article history: Received 11 May 2012 Received in revised form 15 August 2012 Accepted 15 February 2013 Keywords: Breast cancer Trends Africa Risk factors Menopausal status Population-based cancer registry abstract Background: In West Africa, trends and risk factors for breast cancer (BC) have been rarely studied. Methods: Here we have analyzed trends of BC over two periods in two population-based cancer regis- tries, in Mali-Bamako (1987e1997; 1998e2009) and in The Gambia (1988e1997; 1998e2006). We have conducted a caseecontrol study (n ¼ 253 cases, 249 controls) on risk factors associated with repro- ductive life stratified by menopausal status in Bamako. Results: Between the two periods, BC incidence rates increased by 20% (incidence rate ratio (IRR) 1.20 (95% CI [1.07e1.35])) in Bamako, with an annual percentage change of 2% (95% CI [0.4e3.6]). The increase was of 30% inwomen under 55 years (IRR 1.30 (95% CI [1.14e1.60])). A similar pattern was observed in The Gambia for women under 50 years (IRR 1.47 (95% CI [1.07e2.01])). Overall, pre-menopausal breast cancer was predominant in both countries. In contrary to what is well established, caseecontrol study showed that late age at menarche (>14 years) increased the risk of BC among pre-menopausal women (OR: 2.02 (95% CI [1.08e3.78])) while it tended to be protective in post-menopausal women (OR: 0.61 (95% CI [0.29e1.29])). Later age at a first pregnancy (>20 years) was associated with a reduction of risk in pre-menopausal women (OR: 0.41 (95% CI [0.18e0.89])). Conclusion: These results indicate that the burden of pre-menopausal BC is increasing in West African countries. These cancers appear to be associated with distinct reproductive risk factors, highlighting the need for better understanding the biological bases of early BC in African populations. Ó 2013 Elsevier Ltd. All rights reserved. Introduction Worldwide, breast cancer (BC) is the most common cancer among women. 1 This cancer shows important differences in age- related incidences in relation with geography and socio-economic status, perhaps reflecting differences in population structures with a lower average life expectancy among African women, as well as the possible influence of risk factors associated with reproduc- tive life and hormonal status. Other factors such as genetic sus- ceptibility may also play a role. Although breast cancer incidence rate is more than 2.4-fold higher in developed regions (66.4 compared to 27.3 in less developed regions) mortality rate is only 1.4 higher compared to less developed regions (15.3 in more developed regions compared to 10.8 in less developed regions), 2 suggesting that forms of BC with poor outcome are more equally distributed among populations. In recent years, ductal carcinoma of the breast (which is the most common form of invasive breast cancer 3,4 ) has been shown to consist into distinct molecular sub- types with different prognosis and responses to therapy, and may q The work is attributed to the Department of Molecular Carcinogenesis Group at the International Agency for Research on Cancer. * Corresponding author. Tel.: þ33 787517689. E-mail address: pierre.hainaut@i-pri.org (P. Hainaut). Contents lists available at SciVerse ScienceDirect The Breast journal homepage: www.elsevier.com/brst 0960-9776/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.breast.2013.02.011 The Breast 22 (2013) 828e835