Hormone positive breast cancer, also known as hormone receptor-positive (HR+) breast cancer, is a type of cancer that grows in response to certain hormones, such as estrogen and progesterone. When diagnosed with hormone receptor-positive breast cancer, one of the treatment options your doctor might discuss with you is endocrine therapy. Endocrine therapy, also known as hormone therapy, is a common and effective treatment for HR+ breast cancer. It works by blocking the hormone receptors or reducing the amount of hormones in the body. In this blog post, we’ll explore the different endocrine therapy options, their side effects, and the research data supporting their use.

Selective Estrogen Receptor Modulators (SERMs)

SERMs are a class of drugs that block estrogen from binding to its receptors, thereby inhibiting the growth of HR+ breast cancer cells. The most commonly used SERM is tamoxifen (Nolvadex).

Side effects: Hot flashes, vaginal dryness or discharge, mood swings, and an increased risk of blood clots and uterine cancer.

Research data: Multiple studies have shown that tamoxifen can reduce the risk of breast cancer recurrence by up to 40% in premenopausal and postmenopausal women. It’s often prescribed for 5-10 years following surgery.

Aromatase Inhibitors (AIs)

AIs work by reducing the amount of estrogen produced in the body, specifically in postmenopausal women. Women may be offered an AI if they’re in natural menopause or an induced medical menopause. There are three main types of AIs: anastrozole (Arimidex), letrozole (Femara), and exemestane (Aromasin).

Side effects: Joint pain, hot flashes, bone loss, and an increased risk of heart problems.

Research data: Studies have shown that AIs are more effective than tamoxifen in reducing the risk of breast cancer recurrence in premenopausal and postmenopausal women. AIs are usually taken for 5-10 years after surgery.

Ovarian Suppression

Ovarian suppression is a treatment that lowers the amount of estrogen produced by the ovaries in premenopausal women. It can be achieved through medications like goserelin (Zoladex) or leuprolide (Lupron), or through surgical removal of the ovaries (oophorectomy).

Side effects: Menopause-like symptoms, such as hot flashes, vaginal dryness, and mood swings, as well as bone loss.

Research data: The SOFT and TEXT trials demonstrated that adding ovarian suppression to tamoxifen or an AI significantly reduced the risk of breast cancer recurrence in premenopausal women with HR+ breast cancer.

Selective Estrogen Receptor Downregulators (SERDs)

SERDs, like fulvestrant (Faslodex) and elacestrant(Orserdu) work by blocking and degrading estrogen receptors, preventing estrogen from promoting cancer growth.

Side effects: Injection site pain, hot flashes, nausea, and fatigue.

Research data: Studies have shown that SERDs can be effective in treating HR+ metastatic breast cancer in postmenopausal (natural or induced) women, particularly when other endocrine therapies have failed.

The choice of endocrine therapy for HR+ breast cancer depends on various factors, such as menopausal status, tumor characteristics, and patient preferences. It’s essential to discuss these options with your healthcare team to determine the most suitable treatment plan. While endocrine therapies can have side effects, they’re generally well-tolerated and play a crucial role in reducing the risk of breast cancer recurrence and improving survival rates.

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