HRT for Women on Tamoxifen Doesn't Help Hot Flashes

Reviewed study: "HRT for Women on Tamoxifen Doesn't Help Hot Flashes" by I. Sestak and others, San Antonio Breast Cancer Symposium, December 10, 2005, Abstract #19

Is this for me? If you're taking tamoxifen and are having hot flashes, you may want to read this article.

Background and importance of the study: Many women use hormone replacement therapy (HRT) to help lessen symptoms of menopause such as hot flashes. But doctors generally warn women who have had breast cancer not to use HRT. The estrogen in HRT is associated with an increased risk of breast cancer.

Menopause isn't the only thing that often brings on hot flashes. Tamoxifen, a hormonal therapy used to treat breast cancer, also can produce hot flashes and other menopausal symptoms. This happens because tamoxifen blocks the effects of estrogen in many areas of your body. The hot flashes can make you feel miserable and reduce your quality of life. Most women find hot flashes to be the worst side effect of tamoxifen. About half of the women who take tamoxifen are affected by them.

HRT is only occasionally given to women who are taking tamoxifen because of the concerns that HRT might increase the risk of breast cancer. Also, HRT has some of the same serious side effects as tamoxifen: an increased risk of blood clots and stroke. And if you take the two medications together, these side effects can add up.

Many women taking tamoxifen who are having severe hot flashes are desperate for relief. Some of these women would be willing to take on the possible risks of HRT if it meant a better quality of life.

The main purpose of the study reported here was to see if tamoxifen could reduce the risk of breast cancer in women at high risk for the disease. Women taking tamoxifen were compared to women who took a placebo—a sugar pill that looked just like tamoxifen. During the study, the researchers also wanted to find out if HRT would help control the severe hot flashes experienced by some women on tamoxifen.

Study design: The International Breast Cancer Intervention Study (IBIS-I) included 7,154 women age 35 to 70 who were at high risk for breast cancer (but had never been diagnosed with the disease). Women were randomly assigned to take either tamoxifen or a placebo every day for five years. At the beginning of the study, the doctors asked the women about their use of HRT. Each woman was classified as:

• a current user of HRT,
• a former user of HRT (had used it in the past and stopped), or
• a woman who had never used HRT.

The women visited their doctors every six months during the seven years of follow-up. At each follow-up visit, the women gave detailed information about any hot flashes they were having. Some women in each group (tamoxifen and placebo) who had severe hot flashes chose to take HRT in hopes of finding some relief. The researchers then compared users and non-users of HRT to see if HRT works for women taking tamoxifen.

Results: Taking HRT along with tamoxifen did not have a significant effect on hot flashes within the first six months of follow-up. In fact, taking HRT was associated with more hot flashes:

• About 61% of the women taking both tamoxifen and HRT had hot flashes.
• About 49% of the women taking tamoxifen alone had hot flashes.

But women taking the placebo (and not tamoxifen) who also took HRT did have fewer hot flashes in the first six months:

• About 23% of the women taking the placebo and HRT had hot flashes.
• About 34% of the women taking the placebo alone had hot flashes.

After 12 months of follow-up, taking HRT had no effect on the hot flashes of women taking tamoxifen. However, HRT significantly reduced the hot flashes of the women taking the placebo:

• About 20% of the women taking the placebo and HRT had hot flashes.
• About 39% of the women taking only the placebo had hot flashes.

After 7 years of follow-up:

• About 71% of the women taking tamoxifen had hot flashes.
• About 57% of the women taking the placebo had hot flashes.

Most of these hot flashes were reported in the first two months of follow-up. In other words, the hot flashes didn't get worse over time.

HRT was able to significantly decrease hot flashes in women taking the placebo. But in women with hot flashes taking tamoxifen, HRT was unable to make a significant difference.

The comparison between the two groups isn't perfect because the women were not randomly assigned to receive HRT or no HRT — they chose to take it if they wanted to. Still, the results are interesting to many women taking hormonal therapy and dealing with hot flashes who are searching for a solution that works.

Conclusions: The researchers concluded that women taking tamoxifen had no improvement of hot flashes with HRT. Women taking a placebo had a significant reduction in hot flashes when they used HRT.

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