From the Research
No, patients with estrogen receptor (ER) positive breast cancer, even those considered low risk, should not take hormone replacement therapy (HRT) while on aromatase inhibitors. This combination is contraindicated because it would counteract the therapeutic effect of the aromatase inhibitors. Aromatase inhibitors like anastrozole (Arimidex), letrozole (Femara), and exemestane (Aromasin) work by blocking the enzyme aromatase, which converts androgens to estrogens, thereby reducing estrogen levels in postmenopausal women. The purpose of this treatment is to deprive ER-positive breast cancer cells of the estrogen they need to grow. Taking HRT, which contains estrogen or estrogen plus progestin, would directly oppose this mechanism by reintroducing the hormones that the aromatase inhibitors are trying to suppress. Even in low-risk ER-positive breast cancer, adding exogenous estrogen could potentially stimulate cancer cell growth and increase the risk of recurrence, as suggested by the most recent study on aromatase inhibitors versus tamoxifen in premenopausal women with oestrogen receptor-positive early-stage breast cancer treated with ovarian suppression 1.
Some key points to consider:
- Aromatase inhibitors have been shown to reduce the risk of breast cancer recurrence in postmenopausal women with hormone-sensitive early breast cancer 2.
- The use of aromatase inhibitors in premenopausal women with ER-positive breast cancer requires ovarian suppression, and this combination has been shown to reduce the risk of breast cancer recurrence compared to tamoxifen 1.
- Alternative approaches for managing menopausal symptoms that may occur with aromatase inhibitor therapy include non-hormonal medications like certain antidepressants (venlafaxine, gabapentin), lifestyle modifications, and complementary therapies.
- Other preventative therapies for healthy women at high risk of breast cancer, such as selective estrogen receptor modulators (SERMs) and aromatase inhibitors, have been shown to reduce the incidence of breast cancer, but their use is specific to certain populations and requires careful consideration of the risk-benefit profile 3.
In terms of managing menopausal symptoms, non-hormonal medications and lifestyle modifications are preferred over HRT in patients with ER-positive breast cancer on aromatase inhibitors, as they do not counteract the therapeutic effect of the aromatase inhibitors. The most recent and highest quality study on this topic supports the use of aromatase inhibitors in premenopausal women with ER-positive breast cancer treated with ovarian suppression, but does not address the use of HRT in this population 1. Therefore, based on the available evidence and the principle of prioritizing morbidity, mortality, and quality of life, the use of HRT in patients with ER-positive breast cancer on aromatase inhibitors is not recommended.