By Courtney Snavely
I recently re-started the pill after a 5 year affair with my IUD. As a result, I’ve been having a lot of conversations with the women in my life about hormones in the pill and what they're really doing to my body in the long term.
Does it really increase my chances of developing breast or ovarian cancer?
I finally put my academic research background to good use and started to uncover some nuggets of truth in the pill vs. cancer debate. What you’re about to read may shock you!
Okay, so I'm being dramatic. But during my research I came across a lot of news articles that summarized research with a sensationalized headline, i.e. "Oral contraception linked to increased cases of breast cancer." While not a boldface lie, there are a few things to keep in mind when reviewing scientific studies.
1. Correlation is not causation
Speaking statistically, correlation describes a relationship between two variables. For example there is a correlation between lemon imports to the U.S. and highway fatality rates, but this does not mean that more lemons prevented highway deaths. Correlation is different than causation, where one event is the direct result of the other.
When we’re talking about large scale, observational studies (data collected after the diagnosis), it is important to keep in mind we are only looking at correlation and NOT causation. We could see a correlation between cancer and oral contraception (OC), but it is impossible to know that OC was the cause of the cancer.
Cancer has a long latency period. It often takes a long time to develop in the body, leaving an open window for many different factors to affect its manifestation. Cancer is a multifaceted disease and there is rarely one single cause.
2. Research bias
Observational studies have a risk for bias. If a researcher is looking to prove a certain hypothesis, this might influence what data points they think are relevant or how they select certain subgroups to analyze. All of this can influence the quality of the study, the observed correlations, and most importantly the conclusions that are drawn.
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Let's talk about boobs
The New York Times recently published an article titled, Birth Control Pills Still Linked to Breast Cancer, Study Finds.
If we dig into the aforementioned study, the authors state in the first paragraph, “absolute increases in risk [of breast cancer] were small."
"The estimated number of additional breast cancers among premenopausal women that were attributable to hormonal contraception is likely to be low. This risk should be weighed against important benefits of hormonal contraceptives such as good contraceptive efficacy and reduced risks of ovarian, endometrial, and perhaps colorectal cancer (at least for combined oral contraceptives that were commonly used in the 1970s and 1980s).”
Looking at a compiled analysis of breast cancer research, researchers only saw a .89% increase in risk of breast cancer between no use and ever use (using at least one time). They did not see a significant correlation between duration of use (how long you’re taking the pill) and risk of breast cancer and there was a slight decrease in risk the longer the time since women stopped taking OC.
Studies that analyzed risk increase in women already predisposed for breast cancer, carriers of BRCA1 and BRCA2 genes, were inconclusive and showed increased risk in only a subset of BRCA1 carriers.
There is a very teeny tiny increase in breast cancer risk with OC use that differs depending on the hormone mixture of the OC. If you’ve decided the pill is right for you but are still concerned about the (very small) risk, make sure to do breast self-exams and talk with a doctor if anything seems off.
Lets talk about cervixes.
If you thought determining correlation of OC and breast cancer was difficult, it gets even trickier with cervical cancer.
The majority of cervical cancer cases are caused by a persistent HPV infection (usually strain 16 or 18). However, the majority of OC and cervical cancer studies do not select for women who were also HPV positive. In the same meta-analysis, results showed the increased odds of cervical cancer for women who had never used vs. used OC were not statistically significant.
The strength of evidence is insufficient due to lack of studies done with HPV-positive women and poor quality of studies done with HPV-positive women.
*Side note: get your HPV vaccines and make sure you’re getting pap smears according to American Cancer Society guidelines.
What about endometrial cancer?
Finally some data that isn't so damn inconclusive! There is a significant protective effect with OC and endometrial cancer.
Similarly, OC is also associated with a decreased incidence of ovarian cancer. Not to mention, the longer you use the pill, the greater the protective effect.
Everything causes cancer.
The pill (oral contraception) correlated with (NOT CAUSED) a very very very small increase in risk for developing breast cancer. HOWEVER, it is impossible to pinpoint the exact cause of these diagnoses because cancer is multifaceted (other factors may also contribute to this risk) and many of the studies did not account for other risk factors including smoking, BMI, etc.
The pill is not all bad! There are some evidence supported protective benefits linked with oral contraception and endometrial/ovarian cancer.
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It’s important to decide what’s right for you. If you have a family history of or are genetically predisposed to breast cancer, please make sure you are getting regular checkups and examining yourself for any changes in your breasts.
Women are unique and the pill is not for everyone. Hormones can affect people differently; while I don’t mind the daily dose, it might not be right for some women. Figure out what works for you and don't take every headline at face value.
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