Tuesday, September 2, 2014

Hormonal IUDs and Breast Cancer: Is There a Link?


by Sarah Cortez

It certainly goes without saying that birth control has been a major news story the past couple of months. Much of this coverage, of course, has revolved around the recent Supreme Court ruling and reactions to it. Outside of that media storm, there have been some other health-related birth control stories as well, a number of which have focused on the potential of a specific type of IUD - the levonorgestrel IUD - to increase breast cancer risk. 

Photo: Flickr/Theilr
So what do the data actually say about this link? Let’s take a look.

In case you are unfamiliar with the levonorgestrel IUD (brand name Mirena or Skyla), it is a small, plastic, T-shaped device that is inserted into your uterus by a healthcare provider, usually your gynecologist. It prevents pregnancy by releasing a hormone called levonorgestrel and can be left in your uterus for up to five years.

Much of this recent interest in levonorgestrel-releasing IUDs was sparked by a study published in Obstetrics & Gynecology that looked at the records of all 30-49 year old women in Finland who used a levonorgestrel IUD to treat menorrhagia (heavy periods).

The study reports finding that the Finnish women who used the levonorgestrel IUD for 5 years had a 19% increased rate of breast cancer compared to the general Finnish population. That’s bad, right? Well, hold on.

The study also reports that, for these women, ovarian cancer was decreased by 40% and endometrial (uterine) cancer was decreased by 54%. Seeing if the IUD could decrease the risk for, or prevent, endometrial (uterine) cancer was the actual goal of the study.

Remember, these women were receiving a levonogrestrel IUD to treat very heavy periods. Periods, which if caused by endometrial hyperplasia (overgrowth of the uterine lining), put them at increased risk for endometrial cancer. So the study showed that it helped prevent endometrial (uterine) cancer in women who used it to treat very heavy periods.

But, what about the increase in breast cancer?

The authors of the study advised not being too quick to assume that this increase in breast cancer is real. Prior studies have never found an association between levonogrestrel IUD use and breast cancer. So, the finding could just be an outlier or something else could be going on. We don’t know, for example, whether a group of women with very heavy periods has the same breast cancer risk as the general population.

Exactly how this finding translates from Finnish women to American women is also unclear, since the IUDs available in Finland are not exactly the same as those available in the United States

So before you decide to get rid of your IUD because of concerns about breast cancer risk, have an in-depth talk to your doctor. Discuss your family-planning goals, your family history, and your personal risk for breast, endometrial, and ovarian cancer. If your overall risk for breast cancer is low, the levonogrestrel IUD isn’t likely to put you in the high-risk category.

The three most important things women of child-bearing age can do to prevent breast cancer are: be physically active, stay at a healthy weight, and drink only moderate amounts of alcohol – if at all.


Reference

Soini T, Hurskainen R, Grenman S, Maenpaa J, Paavonen J, Pukkala E. Cancer Risk in Women Using the Levonorgestrel-Releasing Intrauterine System in Finland. Obstet Gynecol 2014;124:292-299.

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