What is the role of endocrine therapy in the treatment of breast cancer?

From the Guidelines

Endocrine therapy is a crucial treatment for hormone receptor-positive breast cancer, and its use should be tailored to the individual patient's needs, with a focus on minimizing morbidity, mortality, and improving quality of life. The standard medications for endocrine therapy include tamoxifen (typically 20mg daily) for pre- and postmenopausal women, and aromatase inhibitors such as anastrozole (1mg daily), letrozole (2.5mg daily), or exemestane (25mg daily) for postmenopausal women 1. Treatment duration is typically 5-10 years, with growing evidence supporting extended therapy for high-risk patients 1.

Key Considerations

• For premenopausal women with high-risk disease, ovarian suppression using goserelin (3.6mg monthly injection) or leuprolide (3.75mg monthly) combined with an aromatase inhibitor may be recommended 1.
• Side effects of endocrine therapy include hot flashes, joint pain, bone density loss (with aromatase inhibitors), and rare but serious risks like endometrial cancer (with tamoxifen) or thromboembolic events 1.
• Regular monitoring for side effects and adherence is crucial, as completing the full course of therapy significantly reduces recurrence risk by approximately 40-50% and improves overall survival 1.

Recent Guidelines

• The NCCN Guidelines Panel for Breast Cancer has added endocrine therapy to its recommendations for the neoadjuvant treatment of patients with ER-rich tumors 1.
• The American Society of Clinical Oncology (ASCO) clinical practice guideline focused update recommends adjuvant endocrine therapy for women with hormone receptor-positive breast cancer 1.

Treatment Implications

• The choice of endocrine therapy should be individualized based on the patient's menopausal status, tumor characteristics, and personal preferences.
• Patients with ER-rich tumors may be candidates for neoadjuvant endocrine therapy, which can help reduce tumor size and improve surgical outcomes 1.
• Ovarian suppression or ablation may be considered in premenopausal women with high-risk disease, in combination with an aromatase inhibitor 1.

From the FDA Drug Label

The growth of some cancers of the breast is stimulated or maintained by estrogens. Treatment of breast cancer thought to be hormonally responsive (i.e., estrogen and/or progesterone receptor positive or receptor unknown) has included a variety of efforts to decrease estrogen levels (ovariectomy, adrenalectomy, hypophysectomy) or inhibit estrogen effects (antiestrogens and progestational agents). In postmenopausal women, estrogens are mainly derived from the action of the aromatase enzyme, which converts adrenal androgens (primarily androstenedione and testosterone) to estrone and estradiol. The suppression of estrogen biosynthesis in peripheral tissues and in the cancer tissue itself can therefore be achieved by specifically inhibiting the aromatase enzyme.

The role of endocrine therapy in the treatment of breast cancer is to decrease estrogen levels or inhibit estrogen effects in hormonally responsive breast cancers, which can be achieved through various methods, including:

• Aromatase inhibition: using drugs such as exemestane or letrozole to inhibit the aromatase enzyme, which converts androgens to estrogens in postmenopausal women.
• Antiestrogens: using drugs such as tamoxifen to block the effects of estrogen on breast cancer cells.
• Ovarian ablation: surgical or medical removal of the ovaries to reduce estrogen production.
• Progestational agents: using progesterone-like drugs to inhibit estrogen effects.

These therapies can be used in the adjuvant treatment of postmenopausal women with estrogen-receptor positive early breast cancer, as well as in the treatment of advanced breast cancer in postmenopausal women whose disease has progressed following tamoxifen therapy 2, 3.

From the Research

Role of Endocrine Therapy in Breast Cancer Treatment

• Endocrine therapy plays a crucial role in the treatment of breast cancer, particularly in hormone receptor-positive cases 4, 5, 6.
• The goal of adjuvant hormonal therapy is to prevent recurrence by eradicating micrometastatic disease 7.
• Adjuvant endocrine therapy reduces the risk of recurrence and death from breast cancer in women with hormone receptor-positive early breast cancer 4.

Types of Endocrine Therapy

• Tamoxifen has been the standard therapy for decades, especially for pre-menopausal women 4.
• Aromatase inhibitors (AIs) such as letrozole, anastrozole, and exemestane are superior to tamoxifen in preventing recurrence in post-menopausal women 4.
• Ovarian suppression is also used in combination with AIs or tamoxifen, particularly in premenopausal women 7.

Duration and Benefits of Endocrine Therapy

• Traditionally, treatment has been given for around 5 years, but many women remain at risk of relapse for 10 years or more 4.
• Extended adjuvant endocrine therapy for up to 10 years has been shown to reduce the risk of late recurrence in women still in remission after 5 years of tamoxifen 5.
• The comparative benefits of different endocrine therapy options and the selection of patients most likely to benefit from long-term adjuvant endocrine therapy are important topics for further research 4, 5.

Emerging Trends and Research

• New targets in endocrine-resistant hormone receptor-positive breast cancer are being explored, including targeted therapies and agents under investigation 8.
• Nurses play a vital role in supporting patients in the decision-making process, managing side effects of treatment, and making observations to enhance understanding of the patient experience with new treatments 6.