Could having an abortion increase a woman's risk of breast cancer?
The politically charged question, the subject of more than 30 peer-reviewed studies over recent decades, was supposed to have been put to rest five years ago when one of the largest and most respected studies on the topic found no correlation. Largely based on this research, most epidemiologists now agree there is no link, as does the American Cancer Society, the World Health Organization and the National Breast Cancer Coalition.
But 30 years after Roe vs. Wade, the issue is gaining new currency, as evidenced by a closed-door session two weeks ago at the National Cancer Institute, a respected cancer information resource. Two states, Montana and Mississippi, now include information about a possible link between abortion and breast cancer in materials women receive at abortion clinics. Ten more states are considering similar legislation, according to the Center for Reproductive Rights, a New York-based legal advocacy group. And ad campaigns promoting the theory, sponsored by anti-abortion organizations such as Christ's Bride Ministries, are increasingly popping up on highway billboards, in baseball stadiums and on cable television.
Last year, anti-abortion groups sued abortion clinics in San Diego and North Dakota for telling patients there was no link. A judge dismissed the California lawsuit before trial, while the clinic in North Dakota won its case after a three-day trial. Anti-abortion groups say they plan to file more lawsuits soon.
That the National Cancer Institute, a government agency under the auspices of the Department of Health and Human Services, held a conference at all demonstrates the persistence of advocates on both sides of the debate. Last summer, 22 members of Congress wrote Health and Human Services Secretary Tommy Thompson to criticize the agency's long-held position that there is no link between abortion and a heightened risk of developing breast cancer. With little new research to support the move, the agency modified its position and posted on its Internet site that research on the issue was "inconsistent."
Last week, the institute posted its conclusions from the recent conference on its Web page, saying: "Induced abortion is not associated with an increase in breast cancer risk." An institute spokeswoman said the agency intends to change its Internet fact sheet on the issue.
Even so, some abortion opponents, and at least two scientists who have studied the relationship between abortion and breast cancer, insist there is a link and that the debate has only just begun. Many anti-abortion groups say they will continue their efforts in state capitols, and are confident that a few more states may soon mandate that abortion clinics disclose a warning of a possible link. Others are focusing directly on doctors, from family physicians to gynecologists, hoping to persuade them to raise the issue with their patients directly.
The public relations push is heating up too: One anti-abortion group, the Palos Heights, Ill.-based Coalition on Abortion/Breast Cancer, says it is sending 200,000 pamphlets to churches and others groups nationwide this year highlighting research showing a link.
"We should continue to look at this until everyone is convinced," says Joel Brind, a professor of biochemistry at Baruch College in New York, who has researched the subject and is an outspoken proponent of the theory linking abortion and breast cancer.
Science behind theory
Researchers don't know exactly what causes breast cancer, but reproductive factors have been associated with the disease since the 17th century, when the rate of breast cancer was found to be higher among nuns. Today, scientists believe that childbearing lowers women's breast-cancer risk.
The abortion-breast cancer theory is based on biology, specifically around the interruption of the hormonal flow that occurs in women's breast cells after an abortion. During pregnancy, a surge of estrogen, progesterone and prolactin in the breasts helps differentiate the breast cells and prepare them for lactation. During the second and third trimester, the differentiation permanently changes the breast cells.
Although many scientists dispute the rationale, abortion-breast cancer link proponents argue that when a woman artificially interrupts her pregnancy, she leaves a countless number of undifferentiated breast cells in limbo that increase her odds of developing cancer later in life. Miscarriages are thought to be less worrisome because many are associated with low levels of hormones and thus produce a lower number of vulnerable cells.
Within a decade of Roe vs. Wade, the Supreme Court opinion that legalized abortion in 1973, animal research showed a correlation between abortion and breast cancer. Then, in 1981, a much-publicized study of 163 Los Angeles women, appearing in the British Journal of Cancer, found that women who had an abortion were more than twice as likely to develop breast cancer. But later research wasn't consistent with the British journal's findings, and many scientists began to suspect flaws in the methodology of the British study.
One problem: Almost all of the studies done on the topic were observational "case-controlled" studies, meaning the medical histories of women who were diagnosed with breast cancer were retrospectively tracked and compared with a similar group of women who did not have breast cancer. The drawback to observational studies is that they are based on patients' self-reported recollections of their medical histories -- not medical records or exams. Researchers say that this approach can lead to problems in getting accurate information, especially if the study involves a medical situation that may have some social stigma, such as abortion in the United States.
Scientists suspect that some of the women who had abortions, especially before the Supreme Court made them legal in 1973, might not accurately disclose that history -- a phenomenon in medical research known as "reporting bias." Some of the studies also failed to account for separate breast-cancer factors, such as family history and diet.
Because of reporting and other biases involved in abortion-breast cancer research, "most of the conclusions from [these] case-controlled studies aren't worthwhile," says David Grimes, a clinical professor of obstetrics and gynecology at the University of North Carolina at Chapel Hill, who studied the abortion-breast cancer issue while working as an epidemiologist at the U.S. Centers for Disease Control and Prevention.
In 1996, Brind, of Baruch College, and researchers at Pennsylvania State University revisited the abortion-breast cancer theory by conducting a comprehensive review of all 23 known studies on the issue. Together, the research suggested a 30% increase in breast cancer risk for women who have had at least one abortion. Anti-abortion groups touted the analysis, appearing in the British Medical Assn.'s Journal of Epidemiology and Community Health, as conclusive proof of a link.
Some scientists, however, questioned Brind's research method, arguing that an examination of a lot of small, poorly designed studies might only lead to a larger, flawed conclusion. Others pointed out that Brind is not an epidemiologist, which is more common in research of this kind, and noted his association with some anti-abortion groups. Brind says any implication his political views influenced his research is "ridiculous."
Overall, the U.S. abortion rate is at its lowest level since 1974, according to the Alan Guttmacher Institute, down to 1.3 million from a peak of 1.6 million in 1991. Breast cancer, though, is a different story. Rates of breast cancer in the U.S. have been climbing steadily for more than two decades. Many scientists say better detection and the increase in other known risk factors, such as obesity and environmental causes, may explain part, but not all, of the rise in breast cancer rates.
One woman's story
Charnette Messe, a mother of two from Groton, Conn., was diagnosed with breast cancer last spring. At first, her doctors weren't optimistic about her prognosis, but after she recently underwent chemotherapy and radiation, her doctors believe she may be in remission.
Messe is convinced that an abortion she had 11 years ago is to blame for her cancer. After all, she points out, she doesn't fit into any of the major risk categories: She eats well, exercises often and has no family history of cancer. Messe adds that politics is not playing a role here either. Although she and her husband now oppose abortion, she says she used to support abortion rights until having her children just a few years ago.
"I'm not saying [breast cancer] is my punishment," says Messe. "I just feel in my heart that this illness is because of my regrettable decision."
To escape the epidemiological bias of the previous studies on the topic, from self-reporting or other sources, researchers finally turned toward another study method, known as a cohort study. In this kind of research, women are tracked prospectively, meaning from the time they have an abortion onward to see if they contract breast cancer. But this kind of study takes time, usually decades. Considering the stigma around abortion, there was a second problem: Where could they find a population of women to follow? The answer came from Scandinavia.
In 1997, researchers in Denmark tracked the medical histories of 1.5 million women from 1935 to 1978, based on government data. Denmark has a publicly funded health-care system, and abortion has been legal in the country since 1973. Everyone there is given a numeric identifier, much like a Social Security number, and medical histories can be tracked easily through these registries. The Melbye study (as the Danish research is known), published in the January 1997 New England Journal of Medicine, concluded that there was no increased breast-cancer risk for woman who had an abortion. Because of its size and methodology, many scientists consider the study the best and most definitive research on the subject. Subsequent cohort studies have agreed with the Melbye study, or even shown that abortion may have a protective effect for breast cancer.
But there are plenty of people who remain unconvinced, some of whom attack the methodology of the Melbye study. One problem: The abortion date only went back to 1973, and considering how long it can take for breast cancer to appear, the study may have missed women who hadn't yet developed breast cancer but might later on.
Meanwhile, Messe says the National Cancer Institute's latest statement hasn't changed her belief about the connection between abortion and breast cancer. In January, she traveled to Washington, D.C., and rallied in front of Congress with others opposed to abortion. During the rally, she held up a placard that read: "I regret my abortion."
During the last two decades, more than 30 peer-reviewed studies have come to varying conclusions about the possibility of a link between abortion and breast-cancer risk. Here are descriptions of some of the best-known research efforts and summaries of how scientists and people on both sides of the debate regard them.
Researchers: Pike, et al; published in British Journal of Cancer
Methodology: Retrospectively tracked 163 women, all younger than 32, who were diagnosed with breast cancer from 1973 to 1978. The study relied on participants to self-report their medical histories, including abortion.
Results: Women who reported they had an abortion, or miscarriage, had as much as a 240% increased risk of breast cancer.
Comment: Abortion-rights groups regard the study as too small to be conclusive; they say the study method makes findings subject to reporting bias, especially if the study participants failed to disclose a prior abortion. Abortion opponents praise the research.
Researchers: Daling, et al; Journal of the National Cancer Institute.
Methodology: Compared the abortion histories of 1,700 women, 800 of whom were diagnosed with breast cancer. The study also relied on self-reporting of medical histories.
Results: Risk for breast cancer in women who said they had had an abortion was 50% higher for women older than 18; risk was 150% higher for those younger than 18.
Comment: The study's size and results make it one of the main studies referred to in advertising campaigns promoting the abortion-breast cancer theory. Abortion-rights groups discount the results, calling the study flawed because of reporting bias.
Researchers: Melbye, et al; New England Journal of Medicine
Methodology: Tracked 1.5 million women in Denmark over 43 years by linking data from the country's national abortion and breast cancer registries.
Results: Women who underwent abortion had no higher risk of breast cancer than others.
Comment: Many epidemiologists say that the study's size and reliance on government data instead of in-person interviews make it the best-designed study ever done on the topic. Some scientists and abortion opponents, however, contend that the underlying data were incomplete.
Researchers: Goldacre et al.; Journal of Epidemiology and Community Health.
Method: Tracked 55,000 women from 1968 to 1998 using British public health records.
Result: Having an abortion could have a protective effect against breast cancer.
Comment: Researchers acknowledged that many women in the study weren't classified as having an abortion or a miscarriage. Some scientists say the data are still useful. Other scientists and antiabortion groups say there were likely too many misclassifications for the data to be relevant.