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Abortion and breast cancer risk for Australian women
Author(s) -
Phillips KellyAnne,
Bruinsma Fiona J,
Milne Roger L
Publication year - 2014
Publication title -
medical journal of australia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.904
H-Index - 131
eISSN - 1326-5377
pISSN - 0025-729X
DOI - 10.5694/mja14.01203
Subject(s) - biostatistics , epidemiology , breast cancer , medicine , population , library science , family medicine , cancer , demography , sociology , pathology , environmental health , computer science
TO THE EDITOR: Recent comments in the media have renewed attention on the question of whether abortion is a risk factor for breast cancer, despite broad acceptance internationally in the scientific, medical and cancer advocacy communities that there is no association. It was demonstrated in 2004 that abortion is not a risk factor for breast cancer, based on a combined analysis of prospective cohort study data from around the world.1 The authors showed empirically that retrospective case– control studies tend to give biased findings, most likely because women with breast cancer (cases) are more likely than controls to report previous abortions. Prospective cohort studies avoid this bias because information on abortions is collected before any of the women develop the disease. Indeed, a recent metaanalysis of findings from studies of Chinese women reported an apparent increased breast cancer risk associated with abortion based on case–control studies, but no evidence of association based on prospective cohort studies.2 Several other large prospective cohort studies have published consistently null results since 2004.3,4 In 1990–1994, the Melbourne Collaborative Cohort Study5 recruited 24 018 Victorian women aged 40–69 years who were free of breast cancer, and collected information on risk factors, including all pregnancies. The questionnaire did not differentiate between spontaneous and induced abortions. Using record linkage with the Victorian Cancer Registry, we determined that 1235 of these women were subsequently diagnosed with breast cancer, up to 30 December 2012. We assessed associations prospectively using 3 Henderson KD, Sullivan-Halley J, Reynolds P, et al. Incomplete pregnancy is not associated with breast cancer risk: the California Teachers Study. Contraception 2008; 77: 391-396. 4 Michels KB, Xue F, Colditz GA, Willet WC. Induced and spontaneous abortion and incidence of breast cancer among young women: a prospective cohort study. Arch Intern Med 2007; 167: 814-820. 5 Giles GG, English DR. The Melbourne Collaborative Cohort Study. IARC Sci Publ 2002; 156: 69-70 .