The Faulty Science of the Abortion-Breast Cancer Link

In five U.S. states, physicians are required by law to tell women seeking an abortion about a possible link between induced abortion and increased rates of breast cancer. But there's just one problem: from a standpoint of scientific consensus, that link is mainly bunk. It is, however, a persistent theory, as a round of conservative press promoting a new study on the subject demonstrates. The paper, published recently in the Cancer Causes Control journal, looked at the results of 36 studies in China on what activists have nicknamed the "ABC Link," concluding that women who undergo an induced abortion demonstrate a dramatically increased risk of breast cancer. The Wire asked an epidemiologist to look at the results, just in case the theory finally had the breakthrough it's been waiting for. (Spoiler alert: it hasn't). 

First, some background: the ABC link idea first got going in the 1980s, in the wake of Roe v. Wade. As Slate tells it in an extensive look in the theory, those tentatively proposing a possible link based it on an observation: following the Supreme Court's decision ensuring women have access to abortion, the rates of breast cancer skyrocketed. Although a few early studies seemed to indicate that there could be a link between breast cancer and abortion, further, thorough, inquiries into the subject concluded that such a link stood on extremely shaky evidence.

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But the idea is appealing, especially among those who viewed a perceived "epidemic" of breast cancer among young, sexually-active women as a punitive result of the Roe v. Wade decision. In fact, as Patricia Jasen explains in a survey of the political and historical context of the ABC link research, that initial observation of an increased rate of breast cancer among American women is likely due to more sophisticated early detection methods that coincidentally gained traction during the post Roe v. Wade period. 

This is the context of today's advocacy on the ABC theory. A handful of scientists, such as Joel Brind, a professor of biology and endocrinology at Baruch College in New York, have dedicated their careers to finding ways to prove the link. Brind worked hard to promote the recent Chinese study, claiming that the only reason the ABC link hasn't caught on is because of a vast conspiracy to suppress it. The groups working against the theory, he writes, include: 

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The recent study is not by Brind himself, but by Dr. Yubei Huang et al., whose meta-analysis of 36 Chinese studies concludes that induced abortions increase the risk of breast cancer by 44 percent. For women who have had two abortions, the study claims an increased risk of 76 percent. Those are dramatic numbers. So, what's going on?

Most of the studies use a notoriously misleading method 

"The findings of this meta-analysis should be viewed with caution," Dr. Susan Gapstur told The Wire in an email. Gapstur is the vice president of epidemiology at the American Cancer Society. She notes that almost all of the studies cited in Dr. Huang's analysis used something called the case-control method, which tends to produce misleading results. In the case of the abortion-breast cancer link, women with breast cancer who self-report their reproductive histories tend to do so more accurately than women who are cancer-free. And in countries like China, where abortion still carries a significant stigma, that "recall bias" can be reinforced. "This 'recall bias' can make it look like breast cancer is associated with abortion when it is not," Gapstur explains. Case-control methods, it should be noted, have produced links between breast cancer and induced abortion before. 

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The best studies of the bunch found no link 

All but two of the studies included in Huang's analysis used the case-control method. The remaining two were prospective cohort studies, which track women over time, instead of relying on self-reported historical results. Those two studies, Gapstur notes, did not find a link between abortion and breast cancer. In fact, the eight studies that appear to be the most reliable of the group found no link between induced abortion and breast cancer risk. "The association only became apparent as the quality of the studies decreased," Gapstur told The Wire, noting that some of the included studies were not published in peer-reviewed publications. In other words, the work might not be vetted by independent professionals in the field. 

The ABC link controversy is political, not scientific 

Virtually no reputable scientific institution endorses the ABC link, because the controversy surrounding it has little to do with any room for debate in the data. Inquiries into the subject by the National Cancer Institute, the American College of Obstetricians and Gynecologists, and the Collaborative Group on Hormonal Factors in Breast Cancer based out of Oxford University in England, for instance, have found no evidence of a link between breast cancer and abortion, based on high-quality studies produced on the subject. The American Cancer Association has an explainer on the controversy, clarifying that "the scientific evidence does not support the notion that abortion of any kind raises the risk of breast cancer or any other type of cancer." 

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Based on the evidence, the ABC link should not be one of the divisive elements circling closely to today's debate on abortion. And medical professionals certainly should not be required by law to discuss it as a valid theory. There's a reason the media, and the scientific community at large have ignored studies like these, and it has nothing to do with a cover-up. It's just bad evidence. 

Update: Joel Brind, a professor of biology and endocrinology at Baruch College promoting the study examined here, sent the Wire a lengthy response. Brind takes issue with our point that "scientific consensus" is a meaningful judge of the ABC link's theory, writing that "significant scientific studies almost always go against the scientific consensus." He continues: "If one really examines the so-called 'high quality studies' that do not show the abortion-breast cancer link, and also the critiques I and my colleagues have published in the same, peer-reviewed journals over the years (since 1996), one can appreciate the scandalous abuse of science that has permeated the most prestigious journals in recent years."

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Brind also notes that scientists and activists who believe the ABC link exists will also cite results from a pre-Roe, 1957 Japanese study examining all types of cancers. The authors of that study, according to Jasen, "found slightly higher rates of spontaneous abortion and significantly higher rates of induced abortion among cancer patients, but were hesitant to draw any firm conclusions because of methodological weaknesses in their study." 

Brind concludes: "Finally, Ms. Ohlheiser can't seem to find "any room for debate in the data" on abortion and breast cancer. Nice try, to shut off debate on a real, man-made epidemic that has devastated the lives of so many women in the West, and now threatens the lives of so many millions more in Asia. Add to that the fact that the majority of abortions in Asia are of female fetuses, and one might start to reconsider just who is waging the real war on women." 

This article was originally published at http://www.thewire.com/national/2013/12/inside-faulty-science-abortion-breast-cancer-link/355850/