Birth Control’s Breast Cancer Curveball

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Birth control breast cancer
Hormonal birth control is bad. It just is.

I know there are women who say they took it for decades and it didn’t do any harm to their bodies. It’s possible that’s true for a very small percentage of women. Maybe it didn’t cause any noticeable harm, but I can guarantee it didn’t do anything good for their bodies.

Some new studies have convinced me that you can simply never let hormonal birth control off the hook when it comes to assessing its side effects.

Basics of Breast Cancer

The link between hormonal birth control and breast cancer has been pretty well established over the past few decades. A quick look at the types of breast cancer and a pinch of common sense help us grasp a better understanding of their association.

When a patient is first diagnosed with breast cancer, doctors test for three primary receptors within the tumor to help them identify it. Two of the three receptors are closely related to hormonal contraceptives. The most prolific type of breast cancer contains estrogen receptors (ER-positive). Nearly 80% of breast cancers are ER-positive. The presence of these receptors in a tumor indicates that it will grow more quickly in the presence of estrogens.

The high percentage of ER-positive tumors provides a stark reminder of the warning issued by Dr. Roy Hertz at the Nelson Pill Hearings in 1970:

“[Estrogens] are to breast cancer what fertilizer is to the wheat crop.”

No Safer Birth Control

You might think the safer solution would be to switch to progestin-only birth control. Unfortunately, about 65% of breast cancers contain progesterone receptors (PR-positive). Tumors containing one or both of these two receptors are known as hormone-receptor positive.

Knowing the tumor contains hormone-receptors helps the doctors create a plan of attack. For example, after the initial treatment, doctors will frequently prescribe a drug like tamoxifen to block hormone-receptors and hopefully prevent future metastasis.

The third of the three principle receptors in breast cancer isn’t as easily connected to hormonal birth control. About 20% of breast cancers test positive for human epidermal growth factor receptor 2, commonly called HER2. This protein receptor normally helps control breast cell growth, but when too much of it is produced, it paves the way for an aggressive tumor type.

Triple Negative

Tumors that test negative for all three receptors are known as triple negative breast cancer. This type makes up only about 10-15% of breast cancer cases, but it can be particularly aggressive and prone to relapse. It is also much more likely to metastasize, usually to the lungs and/or brain, and especially in younger women.

Because triple negative tumors test negative for hormone-receptors, doctors have always assumed drugs like tamoxifen would offer no benefit to these patients. But, that’s where things start to get interesting.

Birth Control and Brain Metastasis

A recent study from the University of Colorado Cancer Center stepped outside the box (or in this case, outside the cell) to study the condition of the tissues that surround and support the cancer. Diana Cittelly, PhD, an investigator from the study, offered this explanation, “The cancer cells aren’t responsive to estrogen, but estrogen influences the microenvironment. We found that astrocytes – one of the main components of the microenvironment in the brain – are estrogen-responsive. When they are stimulated with estrogen, they produce chemokines, growth factors, and other things that promote brain metastasis.”

Specifically, they found that estrogen induced the astrocytes to produce two growth factors: brain-derived neurotrophic factor (BDNF) and Epidermal Growth Factor (EGF). These two factors ‘turn on genetic migration/invasion switches in cancer cells,’ making the environment more conducive to metastasis.

Cittelly speculated, “This may explain why breast cancers diagnosed in younger women are more likely to metastasize to the brain – pre-menopausal women have more estrogen, and it may be influencing the microenvironment of the brain in ways that aid cancer,”

While the team didn’t specifically study the effects of birth control hormones, it doesn’t require too much of a leap to carry the speculation a bit further and consider that the flood of estrogens from contraceptives could also contribute to the higher likelihood of metastasis to the brain for women in their reproductive years.

It’s also interesting to note that EGF, Epidermal Growth Factor, a protein that is believed to play a role in how cells normally grow is the same protein that binds with HER2 as one of its receptors.

Surprised, Not Surprised

While we can’t fully understand the interaction of hormonal birth control with EGF and HER2, it would be hard to deny something bad is happening. In fact, the more we learn the harder it is to deny that something bad is going on pretty much anytime it comes to birth control and breast cancer.

In 2015, Breast Cancer Research published a large cohort study, which analyzed pooled data from 54 studies in the African American Breast Cancer Epidemiology and Risk Consortium. Not surprisingly, they found that both recent use and a long duration of hormonal contraceptive (OC) use were associated with an increased risk of breast cancer. They observed increased risks for up to 15 years or more after the women stopped taking OCs.

They compared three types of tumors: ER-positive, ER-negative, and triple negative, and all three demonstrated increased risks. Now, here’s the surprising part. The highest odds were associated with triple negative (TN) tumors. They reported, “Women who had used OCs in the past 5 years were estimated to have a 78% increased risk of TN breast cancer and those who had used OCs for at least 15 years had a 62% increase.”

By comparison, the increased risks related to OC use within the previous 5 years were 46% for ER-positive, and 57% for ER-negative versus non-users. Put another way, the one type of breast cancer that has been most closely linked to birth control because of its obvious estrogen dependence could ultimately pale in comparison to the increases caused in cancer types for which birth control had previously been given a pass.

Continuing Side Effects

Studies like these are what make me uncomfortable when a woman tells me how long she took The Pill and never experienced any side effects. It disturbs me because I fear she is almost certainly singing victory too soon.

As Dr. Victor Wynn warned at the Nelson Pill Hearings, all human carcinogens are latent, and it could take 10 to 20 years of patient history to determine the cancer impact.

And now, with this new curveball, we can’t even rule out its effect on tumors that test negative for hormone receptors.

Read more about birth control’s vast problems in my new book, In the Name of The Pill.

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