Breast cancer is the most common cancer in the UK and accounts for more than a quarter of all cancers in women. 1 in 9 women will be affected. Breast Cancer UK states that only 10% of breast cancer can be attributed to genetic factors. This leaves 90% where the cause is unknown. It has long been established that an early complete pregnancy is a protective factor against breast cancer (1). Keeping a first pregnancy rather than aborting it reduces your risk of breast cancer. In the context of a rising incidence of breast cancer, pregnancy events and breast cancer need to be seriously investigated.
The first study showing a link between abortion and breast cancer was published in 1957 and found a three-fold increased risk (2). In 1981 the issue made news in the UK when a US epidemiologist found a 2.4 increased risk of breast cancer if the first pregnancy is aborted (3). A year later, a flawed study was published to refute this – it did not distinguish between induced abortion and miscarriage as only a handful of women in the study stated that they had an abortion (4). In 1996, a detailed review and meta-analysis of 23 epidemiological studies where abortion and miscarriage were distinguished found a statistically significant increased risk of 1.3 (5). In the context of a high background incidence, this increased risk is significant. In 2000, in defence of this paper which elicited a strong negative reaction in the UK and US, the Royal College of Obstetrics and Gynaecology in the UK stated that this paper has “no methodological shortcomings and could not be disregarded”.
Based on more recent flawed prospective studies, the UK media, abortion industry and Royal College of Obstetrics and Gynaecology (6). claim that there is no link between abortion and breast cancer. It is important to bear in mind that endorsement of poorlydesigned and mistakenly interpreted studies can seriously mislead!
For example, the Danish Melbye Study which claims that there is no evidence of a link on face value seems a strong study being based on a database of all 1.5 million Danish women between 1935-78 (7). But the data on cancer was collected over the last 10 years of this 33 year period, whereas on abortion only over the last 5 years! 60,000 abortions which took place between ‘39 and ‘73 were missed out of the study. Meanwhile, the data on 350,000 younger women aged 15 years to 25 years were part of the study. This younger group, significantly, was far less likely to have developed breast cancer by that age while accounting for a large proportion of the abortions in the study.
The Lancet analysis in 2004 claims that retrospective studies are known to come up with a link between breast cancer and induced abortion, while prospective studies in which recall bias is less likely do not show a link (8). In its conclusions, the Lancet implies that the data from prospective studies are more robust. It proposes that the reason for the link between abortion and breast cancer being seen in retrospective studies is that women who have breast cancer are more likely to disclose that they have had an abortion than those who don’t have breast cancer (“recall bias”). However, in the papers where recall bias was investigated, this hypothesis was refuted (9). I propose another explanation - prospective studies like those considered by the Lancet 2004 analysis and the RCOG guidance in 2004 have methodological and design flaws making them unable to answer the question of whether there is a link. For instance, they do not follow women long enough to see if the cancer develops (should be 30-50 years at least). Some do not take into account the increasing incidence of abortion: they compare older women who are more likely to have breast cancer and less likely to have had abortions with younger women who are more likely to have had an abortion and less likely to have breast cancer; they are therefore unable to demonstrate a link (10,11). A good example of this kind of design flaw is the EPIC study from 2006 quoted in the BPAS journal Abortion Review which has a short follow up period – average 6.6 years! (12). By contrast, the retrospective studies that show a link are comparing like with like – women of the same age, one with breast cancer, the other without. A recent study of this kind which again demonstrated a link is the Turkish case control study, 2009 (13). In summary, opinion-forming bodies should adopt a more critical approach to the studies put forward regarding the abortion breast cancer link: the stakes are high.
Additional comment:
In 2007, a British statistician Dr. Patrick Carroll published a study on predicting female breast cancer incidence in eight European countries using national data. Among seven risk factors, induced abortion was found to be the best predictor of breast cancer incidence (14).
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2. Segi M, Fukushima I, Fujisaku S, et al. An epidemiological study on cancer in Japan. GANN. 1957;48(Suppl):1-63
3. Pike MC, Henerson BE, Casagrande JT, et al. Oral contraceptive use and early abortion as risk factors for breast cancer in young women. Br J Cancer. 1981;43:72-6.
4. UK study Oral contraceptive use and abortion before the first term pregnancy in relation to breast cancer risk. Br J Cancer. 1982;45:327-31
5. Brind J, Chinchilli VM, Severs WB, Summy-Long J. Induced abortion as an independent risk factor for breast cancer: a comprehensive review and meta analysis. J Epidemiol Community Health. 1996;50:481-496
6. http://www.rcog.org.uk/files/rcog-corp/uploaded-files/NEBInducedAbortionfull.pdf
7. Melbye M. Wohlfahrt J, Olsen JH et al. Induced abortion and the risk of breast cancer. N Engl J Med. 1997;336:81-85.
8. Beral V, Bull D, Doll R, Peto R, Reeves G; Collaborative Group on Hormonal Factors in Breast Cancer 2004 Mar Breast cancer and abortion: collaborative reanalysis of data from 53 epidemiological studies, including 83000 women with breast cancer from 16 countries. Lancet. 2004;27;363(9414):1007-16.
9. Daling JR, Malone KE, Vioght LF et al. Risk if breast cancer among young women: relationship to induced abortion. J Natl Cancer Inst. 1994:86:1584-1492. //Lipworth L, Katsouyanni K, Ekbom A et al. Abortion and the risk of breast cancer: a case-control study in Greece. Int J Cancer 1995;61:181-184.
10. http://bcpinstitute.org/beralpaperanalysis.htm
10. http://bcpinstitute.org/beralpaperanalysis.htm
11. Brind J. Induced abortion as an independent risk factor for breast cancer: a critical review of recent studies based on prospective data. J. Of American Physicians and Surgeons. 2005;10:105-110 http://www.jpands.org/vol10no4/brind.pdf
12. Reeves et al, Breast Cancer Risk in relation to abortion: results of the EPIC study. International Journal of Cancer, 2006;119:1741-1745
13. Vahit Ozmen, Beyza Ozcinar, Hasan Karanlik et al. Breast cancer risk factors in Turkish women – a University Hospital based nested case control study, World Journal of Surgical Oncology, 2009;7:37doi:10.1186/1477-7819-7 37
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