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Yes, There's a New Paper on Hormonal Contraception and Breast Cancer
No, there's no reason to panic
The oral contraceptive pill is associated with a small increase in the risk of breast cancer. This is not new. So, it wasn’t that surprising to see a new paper about hormonal contraception, this time looking in greater detail at progestin-only methods, finding a small increase in the risk of breast cancer. However, to those dedicated to promoting pill panic, this was yet another opportunity to stoke fear. Sigh. Their playbook is so predictable. But there isn’t any reason to be scared if you look at this paper in context of what we already know.
Before we go any further…pregnancy is associated with an increased risk of breast cancer, but the pill panic people always conveniently ignore that fact. It has also been shown that the use of hormonal contraception is associated with a lower risk of death overall when compared with people who have never used these methods. And hormonal contraception significantly reduces the risk of ovarian and endometrial cancer. These facts are also conveniently (insert Church Lady voice) ignored. I’ve said it before, with these “pill panic” champions, think various naturopaths, functional nutritionists, period coaches, and the likes of Ricki Lake, as long as your body is in servitude to the patriarchy, meaning breeding, all risks are acceptable.
Most of the data to date on breast cancer and hormonal contraception has been about the estrogen-containing pill, which has long been the most common method. First of all, you should know that the absolute risk of getting cancer while on the pill is quite low. The overall risk that has been calculated is one in 7,690 for women of all ages per year, meaning if 7,690 women take the pill for one year, an additional one will get invasive breast cancer. If we look at women younger than 35 years of age it is 1 additional case of invasive breast cancer for 50,000 women for each year on the pill. The reason the risk is lower if we just look at women under the age of 35 is because breast cancer is so rare in this group.
This translates to an increased risk of 8 - 38% depending on the study, the age of the person, and the number of years on the pill (the 38% is 10 years or more of use). Statistics are funny though, because a 20% increased risk sounds much scarier than the other way of expressing that number, 1 in 7,690. Remember, increasing a tiny number by 20% is still a tiny number. Something the pill panic people always ignore. (I need a better name for them, although pill panic people is sounding pretty good. Asshats works, but it isn’t specific enough).
Until recently, we haven’t had good data on the progestin-only methods, meaning the progestin-only pill, the implant, the Depo-Provera injection, and the hormonal IUD, because until recently they have made up a pretty small percentage of the hormonal contraception market. However, that has been changing over the past 10 or so years, and so a group of researchers in the United Kingdom combed through the UK primary care database and also combined these results with some other data to try to get as many numbers as possible. To control for the possibility that going to the doctor might detect more cancers, they also looked at whether other non hormonal prescriptions, such as antihistamines, had the same risk as hormonal contraceptives.
What they found was a 20% to 30% increased risk of breast cancer risk associated with current use of any hormonal contraceptive, whether it had estrogen or not, and the rate dropped when the medication was stopped. By 1-4 years after stopping, the risk over the baseline was down to 16% and 5-9 years after stopping it was down to 8%, and by 10 years after stopping the risk was back down to baseline. This kind of pattern suggests the hormones are basically kick-starting a cell to become cancerous (and it may take a few years for that effect to be fully realized), but once removed the effect stops. This is in contrast to a carcinogen that causes issues that can be triggered decades after stopping, like smoking. The average time from stopping the method of contraception and developing breast cancer was three years.
Looking at oral contraceptives, both estrogen-containing or without estrogen, the researchers calculated the increased risk of breast cancer for women who took the hormones for 5 years and then in the 10 years after stopping them:
Taking hormonal contraception ages 16-20, an increase of 8 per 100,000 users (from 0.084% to 0.093%)
Taking hormonal contraception ages 25-39, an increase of 265 per 100,000 users (from 2.0% to 2.2%)
This graph from the study helps to put the increased risk of breast cancer in perspective
What is interesting in this study is the risk was the same for the progestin-only IUD. This is something that is puzzling, because hormone levels are significantly lower, and they decrease over time, unlike with the pill. Another database study like this one has also shown an increased risk with the hormonal IUD. It’s always possible that people who are otherwise at higher risk for breast cancer are more likely to choose hormonal IUDs, meaning it’s correlation and not causation, but in truth we don’t know. It seems that we now have enough data with this study to say that the hormonal IUD is likely also associated with the same, small increased risk of breast cancer. And that all methods of hormonal contraception have this low risk that resolves within a few years after stopping.
What Does This Mean for Me?
Nothing in the here and now, because this risk is in line with previous work. Before we has less data on progestin-only methods and now we have more. Research-wise it’s interesting because we need to understand if it is true that a hormonal IUD has the same risk as a pill and, if so, why? This may help us learn more about contraception safety and/or breast cancer. It also seems that the risk of breast cancer with hormonal contraception may not be driven by the estrogen, if it were, the risk for a pill with estrogen and a progestin should be higher than a pill with just a progestin. Understanding this connection can again help us with contraception research as we continually improve the safety, but may also help us understand cancer risks with menopausal hormone therapy, where it seems the progestin plays a big role.
Right now anyone taking hormonal contraception of any kind should assume it carries a very small increased risk of breast cancer that drops back down to baseline within 10 years, although most of the risk is gone after stopping for four years. Contrast that with taking the pill for 20 years and there is a 40% reduced risk of ovarian cancer and a 60% reduced risk of endometrial cancer. And this protection continues for 30–35 years after stopping the birth control pill.
It’s always possible there are biases in these studies, because people aren’t randomized to one type of contraception or another. But as a few of these studies are showing the same level of small risk, it lends credence to their validity. Given how many people are needed to determine breast cancer risk, it’s not possible to collect the data prospectively, meaning enrolling people, letting them choose their contraceptive, and then observing them for years to see what happens. Remember, for people under the age of 35, the increase in breast cancer is 1 in 50,000, so a study would need hundreds of thousands of people on hormonal contraception, but also hundreds of thousands of people not taking any hormones.
In summary, all hormonal contraceptives likely carry the same small absolute increased risk of breast cancer that quickly drops after stopping. This new study confirms, to the best of our ability, that progestin-only methods carry that same risk. And you are likely to live longer taking hormonal contraception.
D Fitzpatrick, K Pirie, G Reeves, J Green, V Beral. Combined and progestagen-only hormonal contraceptives and breast cancer risk: A UK nested case–control study and meta-analysis. PLOS One March 21, 2023.
PC Hannaford, L Iversen L, TV Macfarlane, et. al. Mortality among contraceptive pill users: cohort evidence from Royal College of General Practitioners’ Oral Contraception Study. BMJ 2010;340:c927.
BM Charlton, JW Rich-Edwards JW, Colditz GA, et al. Oral contraceptive use and mortality after 36 years of follow-up in the Nurses’ Health Study: prospective cohort study. BMJ 2014;349: g6356.
LS Mørch, CW Skovlund, PC. Hannaford, et. al. Contemporary Hormonal Contraception and the Risk of Breast Cancer. N Engl J Med 2017; 377:2228-2239
L Iversen, S Sivasubramaniam, AJ Lee AJ, S Fielding, PC Hannaford PC. Lifetime cancer risk and combined oral contraceptives: the Royal College of General Practitioners’ Oral Contraception Study. Am J Obstet Gynecol 2017;216(6):580.e1-580.e9. 3.
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