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Friday, July 20, 2012

The ABC Link


Disclaimer.

Even if all pro-lifers used secular reasoning, there is plenty of room for disagreement in the multi-faceted abortion debate.  Secular Pro-Life takes formal stances on a few issues, but where SPL members—especially SPL leadership—disagree, SPL declines to take an official position.  (See, for example, the rape exception.)

The alleged link between abortion and breast cancer (“ABC link”) is one of these topics.  SPL leadership includes those who believe the science behind the link is sound, those who believe the evidence is mixed, and those (me) who don’t find the evidence compelling.

Therefore, it should be noted that this post does not constitute an official SPL stance.  It is my own view, and I make it in the hopes of promoting an earnest discussion.

It’s easy to believe what you want to hear.

People are generally more accepting of information that supports their personal views.  For example, scientific consensus serves pro-lifers well when we talk about fetal development and the biological beginning of human life.  In my experience, pro-choicers tend to avoid/ignore this information.  On the other hand, scientific evidence seems better suited to the pro-choice perspective when they discuss relative maternal mortality rates between abortion and childbirth.  Again in my experience, pro-lifers tend to avoid or deny this aspect.  As much as I seek to be objective, I know that I also tend to turn a more skeptical eye toward information that undermines the pro-life view than information that supports it.  It’s a common tendency.

But intellectual honesty requires us to think critically about all evidence.  This doesn’t necessarily mean we will all come to the same conclusions.  Earnest people can look at the same evidence and see different patterns.  But our primary goal should be to seek truth, not to support a specific agenda.  If our beliefs are solid, seeking truth should simultaneously support our agenda anyway.  I don’t want to view evidence a certain way because I am pro-life.  I want to be pro-life because evidence leads me to that stance. 


So while it’s true that abortion causing breast cancer would be yet another reason to oppose abortion, intellectual honesty compels me to explain why I don’t find the claim convincing.  (Indeed, I don’t see sufficient evidence for the correlation between abortion and breast cancer, much less causation.  Read about the correlation/causation distinction here; see an amusing graphic about it here.)

Background: The ABC Link Theory.

It is true that women who have never had children or who have them only after age 30 have an increased risk for breast cancer.  This would imply that before age 30, abortion, miscarriage, and never conceiving to begin with all increase the risk of breast cancer. 

It’s important to understand that this is a distinct issue from the ABC link.  The ABC link is the idea that induced abortion increases a woman’s risk of breast cancer as an independent factor.  This would mean induced abortion causes a greater risk of breast cancer than miscarriage or than not ever getting pregnant in the first place. 

I recently wrote about a podcast in which pro-choice atheists greatly mischaracterized the pro-life perspective.  During part of the show the hosts expressed their ignorance as to why some people suggest there is a link between abortion and breast cancer: “Where did this even come from? Is it just completely made up out of nothing?” “I feel like it’s another scare tactic.” “The Big C is the big scary, so let’s bring that specter up.” (14:44)

The abortion/breast cancer connection is not “completely made up out of nothing.”  Proponents of the ABC link suggest a mechanism as follows: 

  • There are three types of lobules in the breast.  Type 1 and Type 2 are cancer-sensitive.  Type 3 lobules, the most mature type, are cancer-resistant, possibly because they replicate DNA more slowly, resulting in less replication error and more time for DNA repair.  When a woman carries a pregnancy to term, during the 3rd trimester her breast lobules mature to the cancer-resistant Type 3 lobules.  By comparison, women who don’t carry pregnancies to term (abortion, miscarriage, and never conceiving at all) have an increased risk of breast cancer.
  • Never conceiving: During the first two trimesters of pregnancy the breast merely enlarges, increasing the numbers of Type 1 and Type 2 lobules, which are cancer-sensitive. For women who never get pregnant to begin with, there’s no increase in cancer-sensitive lobules.  Less risk.
  • Miscarriage:  Most miscarriages occur in pregnancies with low hormonal levels, meaning that there is again little-to-no increase in the cancer-sensitive Type 1 and Type 2 lobules.  Less risk.
  • Abortion: In contrast, most abortions are performed on pregnancies with normal hormonal levels, meaning an increase in cancer-sensitive lobules has already happened, but the final maturation (in the 3rd trimester) to cancer-resistant Type 3 lobules doesn’t occur.  More cancer-sensitive cells.  More risk.

This is the ABC link theory.

Given that studies have shown premature birth can cause an increased risk of breast cancer, and that the risk is correlated to how premature the birth is, the ABC link theory seems perfectly plausible.  Indeed, if premature birth causes an increased risk of breast cancer, I have to wonder why abortion wouldn’t cause an increased risk.

Background: Recall Bias.

In order to determine a correlation, if any, between abortion and breast cancer, researchers must collect women’s reproductive histories (i.e. how many pregnancies, miscarriages, abortions, and live births women have had).  This can be done in multiple ways:

·         Prospective Interview: researchers interview women about their reproductive histories before any of the women have been diagnosed with breast cancer, then monitor who is diagnosed with breast cancer in the years following.
·         Retrospective Interview: researchers interview women about their reproductive histories after the women have been diagnosed with breast cancer, and interview comparable healthy women.
·         Medical Records: researchers collect reproductive histories from medical records instead of interviews.

If all women were accurate about their reproductive histories, we would expect to find the same correlation between abortion and breast cancer regardless of whether women were interviewed before or after diagnoses, or whether the information was taken from medical records.  However, this has not been the caseStudies have found that when information about abortion is collected before women are diagnosed with breast cancer, it appears abortion has no effect or possibly even decreases the risk of breast cancer.  When information about abortion is collected after women are diagnosed with breast cancer, it appears abortion increases the risk of breast cancer. 

Clearly abortion cannot both decrease and increase the risk of breast cancer, so what do these results mean?  In both cases, women had abortions before they were diagnosed with breast cancer; the only difference is whether women were asked about their abortions before or after they found out they had breast cancer. 

The different results may be the product of recall bias.  Some researchers theorize that, compared to breast cancer patients, healthy women are less likely to report their abortions.  The idea is that breast cancer patients will be more forthcoming about their abortions because they hope an increased understanding of their physical history can help them combat cancer.  In contrast, healthy women have little incentive to admit to something as highly stigmatized as abortion. 

If this is true, recall bias could not skew the results of prospective interviews, because the women interviewed don’t know whether they will have breast cancer.  Recall bias could, however, skew the results of retrospective interviews. 

Scientists at the Netherlands Cancer Institute decided to look further into potential recall bias by comparing the number of reported abortions between women from predominantly Catholic regions to women from other regions (the theory being that abortion is less accepted in predominantly Catholic regions).  They found that in the less Catholic regions, women reported similar numbers of past abortions whether they had breast cancer or not.  However, in the predominantly Catholic regions, healthy women reported significantly less past abortions than women with breast cancer.  This suggests that either abortion is more likely to cause breast cancer in some parts of the country than others, or divergent social attitudes toward abortion in different parts of the country affect whether women will report their abortions.  Given that the former makes no sense, the researchers concluded that recall bias is a real problem in retrospective studies of abortion and breast cancer.

So what does the research show?

There have been numerous studies conducted by numerous medical organizations that have found no ABC correlation.  In particular, because of the controversy surrounding the alleged correlation, NCI had this response:
In February 2003, the National Cancer Institute (NCI) convened a workshop of over 100 of the world’s leading experts who study pregnancy and breast cancer risk. Workshop participants reviewed existing population-based, clinical, and animal studies on the relationship between pregnancy and breast cancer risk, including studies of induced and spontaneous abortions. They concluded that having an abortion or miscarriage does not increase a woman’s subsequent risk of developing breast cancer.
(See a summary of the workshop’s findings here.)

However, there has also been research, particularly by Dr. Joel Brind, that has found a significant correlation between abortion and breast cancer.  Additionally, Dr. Brind has criticized some of the studies that have claimed no correlation between abortion and breast cancer. 

But then again, Dr. Brind’s own research has been critiqued, particularly with regards to recall bias:
One issue is how easily Brind et al. dismiss bias. They argue that any bias is unlikely to have been responsible for their finding because there is "consistency across the independent studies," as reflected in the overall result of the meta-analysis. This argument ignores the possibility that a systematic bias may affect all (or nearly all) studies. For Michels and Willett, recall bias remains a viable explanation for the finding of slightly increased risk. They cite survey data and a Swedish study using a registry-based gold standard to show that healthy women consistently and widely underreport their history of induced abortion. Brind et al. discount this same evidence. They also jump from the finding of an association to the conclusion of cause and effect—a leap beyond the bounds of inference.
These are by no means the only criticisms of or by Dr. Brind.  He and other researchers go back-and-forth over the veracity of various conclusions in regard to multiple ABC studies. 

So now what?

Meanwhile pro-choicers and pro-lifers alike emphasize the research refuting or supporting the link, respectively, while accusing the other side of ignoring contradicting evidence. 
Anti-choice zealots have drawn highly questionable conclusions to develop “public education” campaigns… Anti-choice claims linking abortion and breast cancer fly in the face of scientific evidence. - Planned Parenthood 
That truth, like the blood of the aborted children that drenches the ground of our nation, keeps rising up and crying out to be noticed—much to the disdain of Planned Parenthood and its pro-abortion-biased scientists who discredit and trash studies that do not show what they want them to show. – LifeNews.com
I think both of these claims go too far.  Linking abortion to breast cancer “flies in the face” of some scientific evidence, but appears to be a sound conclusion based on other studies.  Reasonable people who simply want to know the truth could review the myriad of ABC studies and critiques and be left feeling uncertain one way or another.  Indeed, when you take a step away from the more highly politicized sites and a bit closer to the original research, it’s readily acknowledged that studies have conflicted.  As the National Cancer Institute states: 
Until the mid-1990s, the evidence was inconsistent. Findings from some studies suggested there was no increase in risk of breast cancer among women who had had an abortion, while findings from other studies suggested there was an increased risk.
However, NCI goes on to explain: 
Most of these studies, however, were flawed in a number of ways that can lead to unreliable results. Only a small number of women were included in many of these studies, and for most, the data were collected only after breast cancer had been diagnosed, and women’s histories of miscarriage and abortion were based on their “self-report” rather than on their medical records. Since then, better-designed studies have been conducted. These newer studies examined large numbers of women, collected data before breast cancer was found, and gathered medical history information from medical records rather than simply from self-reports, thereby generating more reliable findings. The newer studies consistently showed no association between induced and spontaneous abortions and breast cancer risk.
So the evidence is mixed, right?

I can understand people coming to that conclusion.  When a topic is as highly politicized as abortion, it can be hard to tell the difference between truly mixed results and an attempt to hold on to pre-ordained narratives because of bias. 

However, if denial of the ABC link is the result of bias, that bias would have to be rampant.  And we aren’t just talking about the bias of organizations like Planned Parenthood or the National Abortion Federation.  In order to flatly overlook evidence that contradicts the ABC link theory, we’d have to believe that organizations whose main purpose is to combat cancer (National Cancer Institute, American Cancer Society) are overlooking risk factors for cancer in deference to a specific abortion narrative. 

There are conflicting studies, and each side has suggestions as to why the other side’s studies are inaccurate.  If I understand correctly, one side says that recall bias makes there appear to be an ABC link where there is none.  This seems plausible to me.  The other side suggests that pro-abortion bias causes people to emphasize some factors and studies and overlook others.  While also possible, this seems much less plausible to me.

In fact, that sounds suspiciously like a conspiracy theory.  Conspiracy theories are non-falsifiable, immune to contradictory evidence—in short, the very opposite of science.  I think we should avoid that.

Dr. House, however, is fine with conspiracy theories.
While there are conflicting studies, it seems to me that the majority of the more reliably conducted studies have not found a correlation between abortion and breast cancer.  Additionally, it seems the majority of the scientific community is in consensus on this point.

So you’re saying abortion does not cause breast cancer.

Not quite. 

Scientific inquiry often provides more nuanced answers than strong personal beliefs or politics can abide. (Scienc-y cartoon here!) 

Am I absolutely sure abortion has no effect on breast cancer risk?  No.  Am I convinced that the current scientific consensus is that no correlation between abortion and breast cancer has been found?  Yes. 

Many studies have failed to find a significant correlation between abortion and breast cancer.  We don’t know what studies with improved design, sample sets, and follow up will find in the future.  Given the correlation between pre-term birth and breast cancer, and the inverse correlation between full-term birth and breast cancer, I think it’s reasonable for people to wonder, and continue researching the topic.  However, based on my understanding of the studies thus far and of the declarations of most of the scientific community, I am not inclined to believe abortion significantly increases the risk of breast cancer. 

I can understand feeling uncertain about the ABC link.  I don’t understand, though, feeling certain or insisting that abortion increases the risk of breast cancer.

Implications.

If abortion, as an independent factor, does not cause breast cancer, what does that mean for the pro-life movement?

It does mean we need to take care to be accurate in what we say to women in crisis pregnancies.  It’s true that carrying a child to term decreases the risk of breast cancer.  It’s true that there have been many studies on the ABC link, and some have found a correlation and many have found no correlation.  We should not, however, flatly assert that a woman who gets an abortion is greatly increasing her risk of breast cancer, or that she will certainly get breast cancer.  From what I understand of the research, such statements are at best misleading, at worst outright false.

It does not mean, however, that abortion is therefore acceptable.  How abortion relates to breast cancer has no bearing on the fact that abortion destroys a human being in the most vulnerable and dependent stage of development.  The ABC link may inspire a lot of debate within the pro-life movement, but it shouldn’t cause division, because it doesn’t change the bottom line anyway.

17 comments:

Anonymous said...

As I was scrolling down to see who wrote this and saw the pic of House, I knew. :P ~~Jan

Jameson said...

Excellent article.

Elizabeth Erazo said...

I am so glad you posted this. It will be a good resource for future use in discussing the ABC link!

franky said...

brilliant. keep up the good work :D

Creativepowerhouse said...

I agree with your assessment for the most part. But throughout time, we have seen so much corruption uncovered -- from big banks to Wall Street and beyond -- that I would not be terribly surprised to discover that there has been suppression of evidence involved here. I'm saying this after watching the Komen Foundation withdraw its support from Planned Parenthood and then resume it. Where there is such power politically, there is likely to also be corruption. Not conspiracy, but corruption. That being the case, I am still somewhat leary. The abortion lobby is well-financed. I once viewed and compared Planned Parenthood's tax returns to those of the National Right to Life Committee after someone had criticized NRTL for being a huge, wealthy PAC. I was shocked at the difference. PP is a financial giant in comparison. We need to keep that in mind when we analyze the literature that is coming out in these various studies. I'm interested in who funded the studies and whose clout was used to push them through -- that goes for both sides.

JoAnna Wahlund said...

Even the American Cancer Society admits that bcp appears to "slightly increase" the risk of breast cancer, especially in young women. Slate.com explores the connection as well. Dr. Angela Lanfranchi, a breast surgical oncologist and co-founder of the Breast Cancer Prevention Institute, says that the Pill is a "molotov cocktail" for breast cancer.

JoAnna Wahlund said...

Sorry, that's the National Cancer Institute, above, not the American Cancer Society. Haven't had my coffee yet. :)

Anonymous said...

M, great job on clarifying your position on the "ABC link". I particularly liked your emphasis of the importance of intellectual honesty, especially outlined in the second paragraph under "Implications". What a breath of fresh air! Also, I was hoping you would make the point of the very last paragraph--that either way, abortion is still unacceptable in terms of the loss of life--as I kept thinking about that while reading all your excellently thought out and communicated points.

Just yesterday I was thinking about how vulnerable Baby Z is, and how wonderfully patient and loving her parents are with her, especially when she is fussy. (For everyone else, Baby Z is 2 months old.) And I was thinking about how she was really safer when she was in her mother's womb, and how the womb is designed to be a very protected place for the most vulnerable little humans. And about how we have sadly made it a most dangerous place for the most vulnerable little humans. So, so sad to me...

On a lighter note, I got a nice little chuckle on your link for the "The Science News Cycle." :)

JSS

Kara said...

Excellent article. Thank you for detailing the various arguments. I've not looking into it much myself but it is good to have that information. As you say though, the increase or lack there of in risk of breast cancer ultimately does not change the fact that you are killing a person.

M said...

"I'm interested in who funded the studies and whose clout was used to push them through -- that goes for both sides."

I think that would be worth knowing. If nothing else, how studies get funded is just factual information, not speculation.

M said...

How did you embed links in your comment? I didn't know that was possible.

Also, I'm not sure I'm clear on your point. Are you talking about the pill as an aside or are you saying if the pill increases breast cancer than abortion may also increase breast cancer?

M said...

Thank you. Glad you liked it! I think this is the longest post I've yet written. It certainly took the longest to write, and I learned a lot in the process, which is always nice.

Anus Oleary said...

Abortion causes breast cancer because we want to scare women into not having them. We shall represent any data that supports our conclusion while completely ignoring anything that does not. Why? Because we are allied with the christian conservative movement in this country and we support thier goals and political candidates. Our goal is to snag a few supporters by appealing to a group that does not traditionally identify with the christian political agenda, by claiming that our arguments are "secular".

Anonymous said...

The other issue is not just when the pregnancy or abortion occurs (affecting breast cells), but how. As increased hormone levels have been linked to cancer, and chemical abortions are simply high hormone doses, the link between the two becomes common sense. Even hormone replacement therapy is known to be a risk factor for cancer, so obviously chemical abortions are also.

Anonymous said...

I think the best evidence is the Russo animal study. Rats don't lie about previous abortions. Rats that were given abortions were more likely to develop cancer than rats that had babies or virgin rats. Thus, abortion can be linked to cancer.

Julie Wolk said...

Excellent, informative post, as per usual, but I particularly like the bits of humor scattered here and there. Makes me feel like I'm not just reading a science brief. Nicely done!

Anonymous said...

Great job on the article! I love misanthropic drug addicts, so the inclusion of the House reference in this post really appealed to me.