Purpose of Hormone Treatment in Breast Cancer Patients
Hormone therapy is used in breast cancer patients with hormone receptor-positive tumors to improve progression-free survival and overall survival by blocking the stimulatory effects of estrogen on cancer cells. 1
Mechanism and Rationale
- Hormone therapy targets estrogen-dependent tumor growth in hormone receptor-positive breast cancers, which account for approximately 50% of all breast cancers 2
- Treatment works by either:
- Blocking estrogen receptors (using selective estrogen receptor modulators like tamoxifen)
- Suppressing ovarian function in premenopausal women (using LHRH analogs or surgery)
- Reducing estrogen production in postmenopausal women (using aromatase inhibitors) 1
Types of Hormone Therapy
For Premenopausal Women:
- Tamoxifen with ovarian ablation (LHRH analogs or surgery) is the standard approach for those with no prior adjuvant tamoxifen or discontinued >12 months 1
- Ovarian function suppression combined with aromatase inhibitors may be considered after or with ovarian ablation 1
- Tamoxifen alone is beneficial in delaying recurrence and increasing survival 3
For Postmenopausal Women:
- Aromatase inhibitors (anastrozole, letrozole, exemestane) are superior to tamoxifen in first-line therapy regarding response and time to progression 1
- Sequential therapy options include selective aromatase inhibitors, fulvestrant, megestrol acetate, and androgens 1
Clinical Applications
Adjuvant Setting:
- Reduces risk of recurrence by up to 40% in hormone receptor-positive breast cancers 4
- Standard adjuvant tamoxifen treatment is 5 years at 20 mg daily 1
- Third-generation aromatase inhibitors are used only in postmenopausal women 2
Metastatic Setting:
- Endocrine therapy should be the initial treatment for patients with hormone receptor-positive metastatic breast cancer, except in cases of immediately life-threatening disease or rapid visceral recurrence during adjuvant endocrine therapy 1
- Treatment should continue until there is unequivocal evidence of disease progression 1
- Newer combination approaches include adding targeted therapies like CDK4/6 inhibitors (palbociclib) to overcome hormone resistance 5, 2
Treatment Selection Factors
- Hormone receptor status of the tumor (estrogen and/or progesterone receptors) - hormone therapy should only be used in receptor-positive tumors 1
- Menopausal status of the patient 1
- Prior hormone therapy exposure and response 1
- Disease-free interval and extent of disease at recurrence 1
- Presence of life-threatening visceral disease (may require chemotherapy instead) 1
Important Considerations and Caveats
- Hormone therapy should not be prescribed to women with tumors that do not express estrogen receptors 1
- Combined chemo-endocrine therapy is not recommended in the metastatic setting 1
- Resistance to hormone therapy develops in approximately 50% of hormone receptor-positive breast cancers 2
- Regular gynecological examinations are recommended for patients on tamoxifen due to increased risk of endometrial cancer 1
- Treatment decisions should consider the efficacy/risk ratio, especially in terms of toxicity versus survival benefit 1