Timing of Hormone Therapy Impacts Breast Cancer Risk
Posted Feb 04 2011 11:17am
The fact that hormone therapy, particularly estrogen + progestin (E+P) hormone therapy, increases breast cancer risk is well known. However, the impact of when a women starts hormone therapy on her subsequent breast cancer risk is less certain, though previous research has suggested that starting hormone therapy within 5 years of starting menopause might increase breast cancer risk. A newly published breast cancer research study ( free to download ) examined this and other factors on breast cancer risk in more detail.
For this large study, breast cancer researchers analyzed the characteristics of hormone therapy use by over 1 million postmenopausal UK women on their subsequent breast cancer risk. Characteristics like time of initial hormone therapy use in relation to menopause, duration of hormone therapy use, form of hormone therapy, and more were included in this analysis. Some of the findings of this study are outlined below.
Overall Hormone Therapy Use: Compared to women who never used hormone therapy...
Past users of hormone therapy had a small increase (~8%) in breast cancer risk.
Current users overall had about a 68% increase in breast cancer risk.
Current users of estrogen-only (E-only) hormone therapy had a 38% increase in breast cancer risk.
Current users of E+P hormone therapy had a 96% increase in breast cancer risk.
The risk for breast cancer among past users decreased each year after stopping use such that their risk for breast cancer was similar to women who never used hormone therapy within 4 years of stopping hormone therapy.
Timing of First Hormone Therapy Use
For users of E-only hormone therapy, starting hormone therapy 5 years or more after menopause did not increase breast cancer risk. However, starting E-only hormone therapy less than 5 years after menopause increased breast cancer risk by 43%.
In contrast, postmenopausal women who started E+P hormone therapy less then 5 years after menopause doubled their breast cancer risk, while waiting more than 5 years after menopause was linked to a 53% increased breast cancer risk.
For both E-only and E+P hormone therapy, using them for longer than 5 years increased breast cancer risk substantially compared to using them for less than 5 years.
These are important research findings for postmenopausal women who use or are considering using hormone therapy for the relief of menopausal discomforts. It is clear from this study that users of E+P hormone therapy are at a much higher risk of breast cancer than user of E-only hormone therapy. Additionally, starting either hormone therapy less than 5 years after menopause increased breast cancer risk, though the risk remained greater for users on E+P hormone therapy. Waiting 5 years or more past the onset of menopause reduced the breast cancer risk associated with hormone therapy use, particularly for E-only users whose risk was reduced to little or none. Breast cancer risk, though elevated, was lower when hormone therapy was used for less than 5 years. Combined, the best approach, if one chooses to use hormone therapy at all, appears to be choosing E-only hormone therapy, starting 5 years after menopause, and using for less than 5 years. While this might reduce a postmenopausal woman's hormone therapy-linked breast cancer risk; it leaves her looking for alternative ways to ease her menopausal discomforts.