Does a Brief Cessation of Hormone Therapy Lead to a Better Mammogram?

Since we know hormone replacement therapy (HRT) increases breast density, it seems logical that a short break from hormones prior to a mammogram might improve mammographic sensitivity. In fact, some doctors would recommend that women on HRT stop their hormones for as long as several weeks prior to a scheduled routine mammogram.

However, a recent study in Maturitas suggests that stopping HRT for as long as a month before having a mammogram makes no difference in mammographic breast density.

Researchers in the UK enrolled HRT users who were willing to have a mammogram, then stop their hormones for 4 weeks and repeat the mammogram. The mammograms were read by two experienced radiologists and scored for breast density using two different visual methods and two different computer methods.

All told, 44 women completed the study. The researchers found that stopping HRT for 4 weeks made no difference in mammographic density measured either visually or by the computer. In addition, there was no significant effect on breast tenderness during mammography.

The study’s findings stand in contrast to other studies that suggested stopping hormones might be helpful prior to mammography. But these studies were either confined to women with abnormal mammograms or compared groups of women to each other (case controls).

What makes this study especially compelling was that it used women as their own controls, included women who had used HRT for longer than one year, and was in the setting of routine mammograms. In addition, the researchers used several different techniques for measuring breast density, and found agreement among them in their results.

Weaknesses of the study are that it was relatively small, and that duration of HRT use varied within the population studied.

If supported by other studies, these findings are not so good news for women on hormone replacement hoping to mitigate some of the adverse breast effects of their hormones, at least as it relates to mammographic sensitivity and specificity. However, it is good news in that women should not be asked to suffer without their hormones without a proven benefit.

What is Mammographic Breast Density?

Mammographic density is a measure of permeability of x-ray, and an indirect measure of the density of breast tissue. Increased breast density is an independent risk factor for breast cancer, but is more likely a marker for underlying biologic differences in breast composition rather than a pathologic process in itself.

HRT can increase breast density, though not in all users. Intermittent progestin HRT regimens cause less of an increase in breast density than continuous regimens, and new low dose regimens may not increase breast density at all.

I tell my patients that reading a mammogram of a dense breast can be like looking through fog. If there’s an abnormality there, it may be harder to see. By contrast, a mammogram of a fatty breast is like a clear blue sky. Dense breasts are also harder to examine, and I am less confident in my ability to detect small masses in a woman with dense breast tissue on exam.

There’s a lot of active discussion these days as to how to improve breast cancer screening in women with dense breasts. Use of digital mammography, sonogram and MRI may improve detection of breast cancer in women with dense breasts, but the latter two come at a price of increase in false positives and biopsies.

What Should You Do?

Here comes the usual answer – Talk to your doctor. When data in the literature conflict, and there is not a clear recommendation as to which is the best way to go, then it’s really up to you to bat it around with your doctor before making any change in your hormone regimen before a routine mammogram. There is certainly no serious downside to stopping HRT for a short time, and if you’re willing to do so in order to have a better mammogram, then I say go for it.

To be honest, though, I do not routinely advise my patients to stop their hormones before having a routine mammogram. Stopping HRT for as little as a few days for some women can mean re-emergence of bothersome symptoms, including vaginal bleeding.

My experience is that a woman willing to stop her hormones for 4 weeks because she was worried about mammographic density would be a woman who would probably not ever take HRT in the first place. Most of my patients these days who choose to use HRT are truly miserable without it, and living the kind of high functioning lives that would be adversely impacted by a month off HRT. Without proven benefit, I see no reason to ask these women to stop hormones before a routine mammogram.

However, this reasoning on my part is very likely influenced by the fact that I don’t hesitate to order breast sonogram for women with dense breasts on mammography, especially if the radiologist hedges their reading by stating that the breast density “may lower the sensitivity of mammography in this patient.”

But that’s another controversial topic for another day, so stay tuned.
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– Weaver K et al. Does a short cessation of HRT decrease mammographic density? Maturitas. 2008 Apr 20;59(4):315-22.
–Mammogram information from the NCI.
–Improving Breast Cancer Screening– Info from the NCI