Abortion's Deleterious Effects on Women: Abortion and Breast Cancer

For almost a decade, much of the Medical Establishment has firmly resisted the overwhelming evidence that there is a link between induced abortion and a heightened risk of breast cancer (the ABC link). It has insisted that the worldwide research showing women who have had an abortion are more likely to get breast cancer is flawed and unreliable.

However, a systematic review of 10 recent studies which have asserted that there is no ABC link, appearing in the winter 2005 edition of the peer-reviewed Journal of American Physicians and Surgeons (JPANDS), sets the record straight. Dr. Joel Brind, a professor of endocrinology at Baruch College of the City University of New York and president of the Breast Cancer Prevention Institute, concludes that the studies do not in any manner disprove the ABC link. (The article can be read online at http://jpands.org/jpands1004.htm.)

ABC Link Has Long History

Evidence of the ABC link is not new. It has appeared in the medical literature since 1957.
The issue assumed a high national and international profile in 1994, when a study published by the National Cancer Institute (NCI) in its own journal showed a 50% increased risk of breast cancer by age 45 for women who'd had any abortions.

That study, by Janet Daling and colleagues of the Fred Hutchinson Cancer Research Center in Seattle, Washington, also showed particularly alarming risk increases--150%--for women who'd had an abortion under age 18. And if such women also had a family history of breast cancer, the risk increase was reported as extraordinarily high.

The NCI--the largest institute of the National Institutes of Health--has been backtracking ever since. Up until 2003, the NCI called the ABC link's evidence "inconsistent." But in that year, an NCI "workshop" proclaimed that the link's nonexistence was "well established."

That conclusion was reinforced in 2004 with a "collaborative reanalysis" of data published in the prestigious British medical journal, The Lancet. The study concluded that "the studies of breast cancer with retrospective recording of induced abortion yielded misleading results, possibly because women who had developed breast cancer were, on average, more likely than other women to disclose previous induced abortions."

What does this mean? The key here is the word "retrospective," as contrasted with "prospective." In retrospective studies, the data relies on women reporting whether they have had an abortion after having been diagnosed with breast cancer. By contrast, prospective data is collected from medical records before the diagnosis of breast cancer.

Critics of the ABC link argue that women without breast cancer (the "controls" to whom the breast cancer patients are compared in the study) are more likely to deny their abortions than are the breast cancer patients. The theory, as one Swedish research team put it, "is a woman who had recently been given a diagnosis of a malignant disease, contemplating causes of her illness, would remember and report an abortion more consistently than would a healthy control."

This so-called "reporting bias" or "response bias"--the alleged greater willingness of women with breast cancer to acknowledge a previous abortion--would therefore make it look as if having an abortion increases the risk of breast cancer. Consequently, critics charge, abortion only appears to be more common among breast cancer patients.

Since almost all of the studies conducted were of the retrospective type (after women have been diagnosed with breast cancer), the reporting bias argument was a convenient way to dismiss the 80% of worldwide studies showing an ABC link. Never mind that the reporting bias argument has been repeatedly disproved.

What was needed--so the "mainstream" argument went--were studies based on prospective data, i.e., medical records or the equivalent, which preceded breast cancer diagnoses, rather than interviews after the diagnosis has been made. Since 1996, 10 such studies have appeared in the medical literature. These studies have repeatedly reported no evidence of the ABC link, thus fueling the negative conclusions of the NCI and The Lancet "reanalysis."

The JPANDS review by Dr. Brind systematically analyzes the methodology and conclusions of all 10 of the new prospective data-based studies. This includes the largest such study, the 1997 study by Mads Melbye of 1.5 million Danish women, which has been extensively discussed in NRL News. (See, for example, www.nrlc.org/news/2003/NRL03/brind.html.) Suffice it to say that the Melbye study embodied some truly outrageous flaws.

According to the new Brind review, the nine studies succeeding the Melbye study have not fared any better. For example, in another study from Scandinavia--a 2003 study of Swedish women by Erlandsson et al.--most of the women who had abortions were misclassified as not having had any abortions.

An even worse case of massive misclassification due to missing data is a 2001 study from Oxford, England. In that study, Goldacre et al. used both abortion and breast cancer records from the National Health Service.

Unfortunately, the reporting of abortions is particularly poor in England. More than 90% of women with abortions were misclassified as not having had an abortion.

A few of the prospective data-based studies published in the last decade were of American women, but they, too, were inadequate.

And so it goes. The NCI and others use all the negative results of the prospective data-based studies to shore up their conclusion that there is no ABC link. Brind shows how exactly none of them can support such a claim, so serious are their weaknesses and flaws, which he lays out in explicit detail.

Brind concludes,  "Induced abortion is indeed a risk factor for breast cancer, despite the strong and pervasive bias in the recent literature in the direction of viewing abortion as safe for women."