Cancer is one of the leading causes of death worldwide. In particular, breast cancer poses a serious threat to women's health and life. However, advances in medical research have led to the development of highly effective drugs to treat hormone receptor-positive breast cancer. One such class of drugs is known as endocrine therapy drugs (ETDs). In this article, we provide an overview of ETDs - what they are, how they work, common types, benefits and side effects.

WHAT ARE ETDS?

ETDs, also known as hormonal therapies or anti-estrogen therapies, are a class of drugs that work by blocking the effects of estrogen in the body or by decreasing estrogen levels. Estrogen is a hormone that fuels the growth of some breast cancers, known as estrogen receptor-positive or progesterone receptor-positive breast cancers. By blocking or lowering estrogen levels, ETDs slow or stop the growth and spread of these hormone-sensitive breast cancers. They are prescribed as adjuvant therapy (after primary treatment like surgery) or as treatment for advanced/metastatic disease.

COMMON TYPES OF ETDS

There are different types of ETDS that work through different mechanisms:

- Aromatase Inhibitors: They prevent the conversion of androgens (male hormones) to estrogens by blocking the aromatase enzyme. Examples include anastrozole (Arimidex), letrozole (Femara), and exemestane (Aromasin).

- Selective Estrogen Receptor Modulators (SERMs): They bind to estrogen receptors in breast tissue but block estrogen's effects. Tamoxifen is a widely used SERM. Other examples are raloxifene and toremifene.

- Progesterone Receptor Modulators: Drugs like ulipristal acetate work by blocking progesterone receptors.

- Gonadotropin-Releasing Hormone (GnRH) Analogues: Drugs like goserelin acetate and leuprolide acetate work by blocking the production of estrogen and progesterone from the ovaries. They are used pre-menopausally along with other ETDs.

BENEFITS OF ETDS

ETDs have proved highly beneficial for the treatment and management of hormone receptor-positive breast cancers:

- They reduce the risk of recurrence in the breast and occurrence of new cancers in women with early-stage disease who have completed primary treatment like surgery and chemotherapy.

- For metastatic disease, they help control tumor growth, slow progression, and improve survival outcomes and quality of life when used along with other anti-cancer drugs.

- When started after surgery, ETDs can reduce the risk of recurrence by as much as 50% over about 5 years of use for some drugs.

- Their adjuvant use has contributed greatly to improved survival rates in hormone receptor-positive breast cancers over the last few decades.

SIDE EFFECTS OF ETDs

While highly effective, ETDs can produce both short and long-term side effects like:

- Menopausal symptoms: hot flashes, night sweats, vaginal dryness in pre-menopausal women.

- Fatigue and weakness.

- Changes in sex drive and sexual problems.

- Joint/muscle pain, stiffness.

- Osteoporosis (thinning of bones) with long term use.

- Rare side effects: Blood clots, peripheral neuropathy, memory issues.

- Aromatase inhibitors can cause arthralgia (joint pain) more commonly than tamoxifen.

- Close monitoring and supportive care from doctors can help manage and minimize side effects.

PRECISION MEDICINE APPROACH

newer targeted therapies are being developed based on genomic profiling of cancers. Drugs like palbociclib and ribociclib, used with an aromatase inhibitor, have shown promising results for advanced ER+/HER2- breast cancers with certain mutations. Genomic tests can identify women who are most likely to benefit from these ‘targeted’ combinations upfront or after disease progression on standard ETDs. This represents a shift toward a more personalized, precision oncology approach.

CONCLUSION

In conclusion, ETDs have revolutionized the treatment of hormone receptor-positive breast cancers and significantly improved survival over the last few decades. Though not curative, they offer durable control when used appropriately. With continued research, newer and more effective endocrine drugs with improved tolerability and targeted options are being developed. Precision genomic profiling will enable oncologists to customize ETD treatment based on individual tumor characteristics. Overall, ETDs provide an important therapeutic option and have become the mainstay of both early and advanced breast cancer management.

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