The abortion-breast cancer connection.

• Author: Brind, Joel

ABSTRACT: This article examines the abortion breast cancer link in some historical scientific detail, offering a perspective on an issue that is at the center of a long-running public policy debate that plays out in legislatures, courtrooms, and newspaper editorials, as well as in scientific and medical journals. Even as politically correct studies have been promulgated to neutralize the data proving the abortion breast cancer link, even stronger data have emerged in recent years that firmly link abortion to premature births in subsequent pregnancies, which in turn raise the risk of breast cancer in mothers and cerebral palsy in prematurely born children.

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The reputation of abortion as safe for women--which claim is explicitly part of the Roe v. Wade decision--has rightfully come under serious question for many reasons over the years since Roe. One of the reasons that "safe abortion" has come under question is the evidence linking abortion to an increased risk of breast cancer (ABC link). The ABC link has been an issue that has been in and out of the limelight in recent years. It is an issue which has stubbornly refused to go away despite recurrent pronouncements from high places of its nonexistence.

A recent example is a 2004 article in the prestigious British medical journal The Lancet. (1) The paper was promoted by the mainstream media as "a full analysis of the current data." (2) According to the byline on the paper, the results of all these studies were compiled into a "collaborative reanalysis," by the "Collaborative Group on Hormonal Factors in Breast Cancer," a group of authors too numerous to list. However, a small print footnote reveals that the study was actually put together by a group of five scientists at Oxford University, headed by prominent British epidemiologist Valerie Beral. The Beral study's conclusion is unequivocal: "Pregnancies that end as a spontaneous or induced abortion do not increase a woman's risk of developing breast cancer." (3) This conclusion is remarkably reminiscent of the National Cancer Institute's (NCI) statement given on its "Cancer Facts" web page on "Abortion, Miscarriage, and Breast Cancer Risk," carried on the NCI website since the spring of 2003. (4) On this "fact sheet," the NCI concludes that "having an abortion or miscarriage does not increase a woman's subsequent risk of developing breast cancer."

The trouble is, to accept this conclusion, one needs to dismiss almost half a century's worth of data which do show a significant link between abortion and an increased risk of breast cancer. Beral et al. suggest that those previous studies "yielded misleading results," (5) and that one should trust the largest, most recent studies (i.e., those which show no ABC link). Such apparently knowledgeable pronouncements seem just a bit too self-assured in an age when concerns about women's health reign supreme.

If one can be certain of anything about the ABC link, it is surely that the question of its very existence is important enough for a careful evaluation, given the millions who choose abortion and the tens of thousands who die of breast cancer each year. The present work will therefore examine the ABC link in some historical and scientific detail, offering a perspective on an issue that is at the center of a longrunning public policy debate that, having been sucked into the maelstrom of the "abortion wars," plays out in legislatures and courtrooms and newspaper editorials, as well as in scientific and medical journals.

Early History of the ABC Link

Neither the ABC link nor the efforts to suppress it are new; the first published study to document it occurred almost half a century ago. Over the years, denial of the ABC link has become the party line of all major governmental agencies (including the World Health Organization (6) [WHO]), mainstream medical associations (including the American College of Obstetricians and Gynecologists (7) and Royal College of Obstetricians and Gynaecologists (8), and the most prestigious medical journals (including the New England Journal of Medicine (9)).

A 1957 nationwide study in Japan (published in the English language Japanese Journal of Cancer Research) reported that women who had breast cancer had a three-fold higher frequency of pregnancies that had ended in induced abortion. (10) As abortion was neither legal nor common in many places, however, such studies were few and far between. But in 1970, a very high profile, multinational WHO study, based at Harvard, and published in the WHO's own Bulletin, reported a disturbing trend "in the direction which suggested increased risk associated with abortion--contrary to the reduction in risk associated with full-term births." (11) The WHO study findings were not based specifically on induced abortion, including both induced abortions and miscarriages, but it is interesting that they came out just about the time when, in the United States and elsewhere, the question of legalization of induced abortion was being widely considered. The fact that the WHO findings never entered the debate reveals a disturbing--and continuing--disconnect between the so-called women's health advocates pushing for legalized abortion, and any genuine concern for women's health.

The first epidemiological study on American women to consider the ABC link specifically was published in the British Journal of Cancer (BJC) by Malcolm Pike and colleagues (12) at the University of Southern California in 1981. Since abortion had only been legal in the United States for scarcely a decade by then, the only appropriate candidates for the study were women diagnosed with breast cancer by their early thirties. In other words, the subjects needed to have been young enough to have been exposed to legal abortion. The results of the Pike study made headlines: women who had an abortion before they had any children were at a 2.4-fold (i.e., 140 percent) increased risk for breast cancer.

The response of the scientific community to the Pike study was dichotomous: reflective of responsible concern from some quarters, and of active denial from others. Exemplifying the former was a 1982 review in the prestigious journal Science by Willard Cates, Jr. of the Centers for Disease Control and Prevention (CDC). (13) Writing on the overall, roughly decade-long history of the safety of legal abortion in the United States, Cares expressed his concern: "There is some concern about ... possibly higher risks of breast cancer in certain women." Exemplifying the effort to deny the ABC link, however, was a 1982 study published in the BJC by a group from Oxford University (interestingly, with overlapping authorship with the 2004 Oxford [Beral] "collaborative reanalysis"). (14) The 1982 Oxford study targeted Pike's study specifically, and claimed greater credibility for its much larger number of patients (1,176 compared with 163 in the Pike study) and much greater age range (up to age 50, compared with a maximum age of 32 in the Pike study). The Oxford group's conclusion was as noteworthy for its emotional tone as for its contrary result: "The results are entirely reassuring, being, in fact, more compatible with protective effects than the reverse." Scientifically, it is a simple matter to explain the Oxford group's negative result: It was based almost entirely on miscarriages, as so few of the women in the study had been young enough to be exposed to legal induced abortion. The biological differences between these two events are clear, and will be discussed in some detail a bit later on in the present paper. It was also particularly telling that, in a paper based entirely on quantitative data, the only quasiquantitative expression in the entire text (or tables) for the number of women in the study who had actually undergone an induced abortion was "only a handful of women." Clearly, this Oxford "study" was little more than a fabrication of apparently negative data, designed to "reassure" the public about the safety of abortion.

The Biology Behind the Statistics

One would think, especially given the overwhelmingly elective nature of induced abortion, that the precautionary principle would prevail, if not in terms of legal regulation, then at least in terms of recommendations by medical societies and public health agencies. That is to say, even one or two studies showing a significant association between induced abortion and future breast cancer risk would surely raise some red flags about the procedure's safety. Not only was a statistical connection showing up in the vast majority of studies that had examined the issue, but by the early 1980s, a clear picture of the physiological events explaining that connection was beginning to emerge.

One important line of evidence providing biological support for the ABC link came from the field of reproductive endocrinology (the study of the hormones of reproduction). Only during the 1970s did laboratory methods for measuring such hormones as estradiol (the main active form of estrogen) and progesterone easily and cheaply become widely available. In 1976, a landmark study by two Swiss obstetricians, Kunz and Keller, was published in the British Journal of Obstetrics and Gynaecology. (15) The Kunz and Keller study documented a clear difference between the enormous rise of estrogen and progesterone in the first trimester of viable pregnancies, and the stunted and short-lived rise of these hormones during pregnancies destined to abort spontaneously (miscarry). These findings dovetailed perfectly with the patterns of differences in breast cancer risk following different pregnancy outcomes that were now clearly emerging from the epidemiological data.

During the same period of the late 1970s, key experimental research on laboratory rats was providing another avenue of verification of the ABC Link. Jose and Irma Russo, a prominent husband-and-wife research team at the Michigan Cancer Foundation in...