Hormone Replacement With Estrogen/Progestogen Combo Increases Breast Cancer Risk More Than Once Thought

September 6, 2017 · Posted in Risk Factors 

breast exam

A 2016 article in the British Journal of Cancer suggests that previous studies underestimated breast cancer risk in women who received hormone replacement therapy with the combination of estrogen and progestogen. The article by researcher Michael E. Jones and colleagues reported that combined hormone replacement therapy could increase the risk of breast cancer by more than three times, depending on how long a woman is exposed to the therapy. The longer the duration of use, the greater the risk of breast cancer. In the study, women who used other types of hormone replacement therapy, such as estrogen only or tibolone, did not have drastically higher rates of breast cancer than had been reported before.

Jones and colleagues suggest that previous studies did not use long enough follow-up periods to track whether women developed breast cancer while using hormone replacement. Their own study is based on a United Kingdom dataset known as the Breakthrough Generations Study. Study participants completed questionnaires at 2.5 years after recruitment, again at around 6 years, and again around 9.5 years. At the time of recruitment, women using combination hormone replacement therapy had been doing so for a median of 5.5 years.

Women who used combination hormone replacement therapy for 5.4 years were 2.74 times likelier to have breast cancer than those who didn’t receive hormone replacement. Using the combined therapy for more than 15 years increased risk 3.27 times compared to non-users.

The study also reported that as body mass index increased, breast cancer risk increased, regardless of hormone use.

While the study by Jones and colleagues was large (39,183 participants), the number of women who took combined hormone replacement and developed breast cancer was still fairly small (52). Seven of the 52 had taken the combined pill for more than 15 years. One limitation of this study is that these seven women may have skewed the risk assessments somewhat.

Experts suggest that women balance the possible risks and benefits of hormone replacement therapy. The therapy can be helpful in reducing symptoms of menopause, particularly hot flashes.

Using the lowest effective dose for the shortest time possible may be the best option. The increased risk of breast cancer drops after a woman stops using hormone replacement.


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