Breast Cancer & HRT

This helpsheet explores the links between early menopause, HRT and breast cancer risks. The objective is to assess the risks from a younger woman’s perspective. Breast cancer, of course, is something that worries so many women, particularly those on hormone replacement therapy (HRT).

Several historical studies linked estrogen with an increased risk of breast cancer. Debates followed about the safety of HRT and whether the benefits outweigh the risks. This had led to continual coverage about a very real — and worrisome — topic.

These older studies examined the effects of long- and short-term HRT usage in postmenopausal women. That means the women participating in these trials are, on average, significantly older than those experiencing early menopause or POF.

What then is the bottom line for women experiencing menopause at a much younger age, many of whom will be on HRT for many years before the “normal” age of menopause?

What are the risks and how does one read between the lines of these studies to assess the situation?

A Brief Overview

The first — and most important thing — to keep in mind is that there are crucial differences in the effects and outcomes of HRT in women of different ages and circumstances. Historical and much publicized studies have focused on women in their 50s and older who are extending their exposure to estrogen.

In effect, they are supplementing their bodies with estrogen beyond the “normal” age of menopause. It’s this prolonged exposure that appears to increase the risk of breast cancer. In other words, women who use HRT at older ages have the greatest elevated risk of developing breast cancer as a result (1).

Younger women — women who have premature ovarian failure (POF), early menopause, or surgical menopause are not dealing with the same situation. They’re effectively replacing hormones that they might otherwise have expected to have until they reached the average age of menopause.

In fact, when administering HRT, the aim in early menopause is generally to mimic the “normal” daily ovarian production rate of estradiol — i.e to closely simulate what is the average level for women of the same age. That is, what women with normal ovarian function experience across their menstrual cycle (2).

It’s also important to remember that if you’re currently on HRT due to early menopause or POF, your cancer risks aren’t necessarily increased to the levels that appear in the studies because, as a younger woman, you start out with a much lower underlying risk of breast cancer to begin with than that of the older women involved in the studies.

To make a rough comparison of odds, the average 35-year-old woman has approximately a 1 in 200 chance of developing breast cancer within the next decade, while a 55-year-old woman has around a 1 in 33 risk in the same timespan — quite a large difference (3).

Remember, you should always talk to your doctor about your concerns — and carefully weigh your personal risks. Breast cancer risks are clearly not something to be overlooked. It’s the most common cancer affecting Western women.

By the age of 75, about one in every thirteen women will get breast cancer, and the chances for an individual are elevated when there’s a family history of the disease.

The official position of the American Cancer Society is that estrogen-only HRT is not linked with an increase in breast cancer risk. Meanwhile, the official position of Cancer Research UK is that HRT slightly increases the risk of breast cancer. However, they also state that “for most people, the benefits of taking HRT outweigh the risks.” These blanket advisories apply to menopausal women in general and therefore of all ages.

The Estrogen-Breast Cancer Connection

The concerns about estrogen replacement being linked to increased breast cancer risk began because certain cancerous tumors have estrogen-receptor proteins. Scientists have hypothesized that this type of tumor may grow more rapidly if you are taking estrogen (4, 5).

Thus, one theory about the link between estrogen and breast cancer is that it may cause cancer cells already in breast tissue to multiply at a heightened rate.

Nevertheless, there may be a link between lifetime estrogen exposure and breast cancer risk (6).

It’s important to remember, however, that the increased risk of breast cancer following HRT use appears to be greater in older women (7). In addition (if indeed a link exists), the increase in risk is small, according to the official position statements of both the American Cancer Society and Cancer Research UK.

A Closer Look at What the Risk Numbers Mean for a Woman in Early Menopause

So what does all this mean for you?

Of course, it’s one thing to see news headlines, but another thing to actually understand what the numbers really mean. And, on the whole, media reports have tended to sensationalize the threat posed by HRT.

Put simply, the headline figures used in many reports following the WHI study referred to relative risk. These numbers tend to illicit fear because they fail to reflect the actual “absolute” risk of a negative outcome occurring.

In summary, it’s important to understand that the studies that have been done mostly deal with women age 50 and over. In cases of early menopause, of course, what we really want to know is what these risks are for younger women.

The actual risk of breast cancer for a woman age 20 to 40 — that is, the usual age of someone coping with early menopause or premature ovarian failure (POF) — is much lower than in older women. At an individual level, this risk may be higher or lower depending on things like your health status, genetics and family history.

As a younger woman, on average you are at a much lower risk of developing breast cancer at baseline than the women who have been studied (for example, in the landmark WHI study).

Additionally, going through early menopause or premature ovarian failure (POF) may actually reduce the risk of breast cancer compared to the general population. Studies have shown that women who go through menopause before the age of 51 have a lower risk of breast cancer than their peers (8).

By the same token, women who keep having periods past the average age of menopause may face an increased risk of breast cancer compared to their postmenopausal peers (9).

The general rule of thumb, then, is that the pros and cons “equation” for taking HRT is different for women in early menopause than it is for women going through menopause at the “normal” age. Naturally, your doctor is the best person with whom to discuss these benefits and drawbacks, but authoritative sources maintain that short term estrogen HRT has a favorable risk vs benefits profile for younger women (10).

Furthermore, most specialists now advocate starting HRT upon diagnosis and continuing up to the “normal” age of menopause in women with POF (11, 2).

Since experiencing an early menopause reduces your lifetime estrogen exposure, HRT use brings your exposure back to levels similar to a woman who has normally functioning ovaries and regular estrogen levels.

Early menopause comes with certain elevated risks not faced by older menopausal women that we often must be proactive in tackling. Women going through early menopause or premature ovarian failure (POF) do have a much greater risk of bone loss and cardiovascular issues, risks that HRT may help to tackle (11).

Of course, once you do reach the age of “normal” menopause — around 50 — it’s a good time to reevaluate the situation and your HRT use. Up to that point, however, your best course of action is frank and forthright discussion with your doctor while you figure out a treatment plan that suits your needs.