- Estrogen is to breast cancer what carbon dioxide is to global warming--with a twist.
- CO2 is a "greenhouse gas" that traps heat, so anthropogenic global-warming ("AGW") theorists argue that the rise in temperatures around the world is the result of humans burning fossil fuels.
- Steroidal estrogen is a recognized carcinogen. Pregnancy loads a woman's body with estrogen, but abortion interrupts the process before other hormones can mature breast tissues. Abortion/breast cancer ("ABC") theorists argue that this can explain the global epidemic of breast cancer since oral contraceptives and abortions became common.
- The twist: people who question the AGW hypothesis are called "deniers" and are told "the science is settled." People who articulate the ABC hypothesis are called "fanatics" and are also told "the science is settled."
Research on Rats
- Pro: Rat breast tissue is more susceptible to mutations in early pregnancy, which raises the risk of cancer. Fortunately, breast tissue becomes specialized in later pregnancy, which reduces the lifetime risk of cancer. Rats that give birth have a lower incidence of cancer, but research shows that interrupted pregnancies confer no protective effect. Although the A/BC link was first hypothesized in 1957, nobody has done a study on rats that is specifically designed to find out whether induced abortions raises the risk of cancer.
- Con: Rats aren't people. The science is settled. We don't need more research.
Research on Pregnancy
- Pro: The age at first live birth is a well-known risk factor for breast cancer. Earlier is better--the sooner a woman has a baby, the lower is her lifetime risk of breast cancer. This is true despite the fact that child-birth itself
raises a woman's risk of breast cancer in the 15 years after birth. This transient risk is due to the impact of estrogen on breast tissue. Abortion leaves a woman with the worst of both worlds--all the elevated risks of pregnancy without the protective effects of birth.
- Con: Women don't care about raising their risk of cancer when
they're considering terminating their pregnancy, and doctors shouldn't
tell them about it. It would only confuse and distress them.
Research on Estrogen
- Pro: The suspected link between abortion and breast cancer is based on the high levels of estrogen during pregnancy. Estrogen has been tied to breast cancer time after time. Hormone replacement therapy is a recognized breast cancer risk. Steroidal estrogen is a recognized carcinogen. Injectable contraceptives appear to raise breast cancer risk. Studies on oral contraceptives have been more controversial, but the World Health Organization identifies estrogen-containing oral contraceptives as a "Class 1 carcinogen."
- Con: Only Catholics object to oral contraceptives. This is just another case of religion hiding behind the mask of "science."
Research on Populations
- Pro: Breast cancer is rising around the world, especially in
populations that have begun to use oral contraceptives or induced
abortion. Breast cancer incidence is elevated in every group that tends
to choose abortion: (i.e., young black women, more educated women,
higher status women, etc) and lower in most groups that tend to avoid
abortion (older black women, more religious women, Hispanic women in
Hispanic neighborhoods, etc.).
- Con: Claims of a "global epidemic" of breast cancer have been
overblown. Most of the alleged increase in breast cancer in the United
States is simply the result of better publicity and longer lifespans.
Breast Cancer Studies:
Case-Control Studies: Matching women with breast cancer to otherwise-identical women
- Pro: Study after study finds a modest increase in breast cancer risk. The studies that distinguish women who had abortions from women who took the Pill are consistent with an increase in risk of 3% per week of terminated pregnancy. Studies designed to correct for the possibility of "recall bias" fail to find any.
- Con: Any apparent increase can be explained by "recall bias," which holds that women who get sick tell the truth while women who are healthy tend to maintain their privacy.
Cohort Studies: Following large groups of previously-identified women over time
- Pro: Cohort studies, which track large groups of women over
time, necessarily fail to address the multiple variables that affect
breast cancer risk. Studies funded by big drug companies should be
scrutinized as carefully as studies by tobacco companies.
- Con: Cohort studies are the most reliable because they are the largest and are not subject to recall bias.
Recall Bias: Do Healthy Women Conceal Abortions?
- Pro: Janet Daling, of Seattle's Fred Hutchinson Cancer Research Institute, is personally pro-choice but is even more anti-cancer. Her research on the abortion/breast cancer link was elegantly designed to detect any evidence of recall bias. She included three groups of women in her study: some with breast cancer, some with cervical cancer, and some who were healthy. The recall bias theory suggests that women with cancer (whether breast cancer or cervical cancer) would tell the truth, while healthy women might be shy. She found no evidence of an increase in risk among women with cervical cancer, but a statistically significant increase among women who chose abortion.
- Con: Recall bias explains all the apparent increase in risk.
Hypothesis Or Theory?
- Pro: Before the National Institute of Health convened its panel to discuss this issue in 2003, almost every paper on the topic concluded with "more research is needed." The research done since then is consistent with a modest, transient increase in breast cancer risk after induced abortion as long as one recognizes the confounding effect of oral contraceptives. With the latest meta-analysis from China, it's time to stop calling this the "abortion/breast cancer hypothesis" and recognize it as a valid scientific theory.
- Con: The hypothesis has been disproved. The science is settled. The continuing obsession about this is just more right-wing, anti-choice obfuscation.
The link between abortion and breast cancer has been so vigorously and officially denied that many people have decided it simply must be false. Talking about abortion and breast cancer these days is like insisting that Obamacare will create "death panels" or denying global warming.
That's why the new Chinese research matters. It's time for open-minded people to review the arguments and make up their own minds. This page is a place to begin the discussion.