| Drug Class |
SERM |
SERM |
GnRH (LHRH) agonist |
Aromatase inhibitor |
| Mechanism of Action |
Estrogen receptor antagonist in breast; partial agonist in endometrium & bone |
Estrogen receptor antagonist in breast & endometrium; agonist in bone |
Suppresses LH/FSH → decreases estrogen/testosterone production |
Inhibits aromatase enzyme → lowers estrogen synthesis |
| Indications |
ER+ breast cancer (adjuvant, metastatic), breast cancer prevention (pre & postmenopausal) |
Breast cancer prevention (postmenopausal), osteoporosis |
Premenopausal ER+ breast cancer (ovarian suppression), prostate cancer |
Postmenopausal ER+ breast cancer (adjuvant, metastatic) |
| Patient Population |
Pre- and postmenopausal women |
Postmenopausal women only |
Premenopausal women (breast cancer), men (prostate cancer) |
Postmenopausal women only |
| Route & Dose |
Oral 20 mg daily |
Oral 60 mg daily |
Subcutaneous depot: 3.6 mg monthly or 10.8 mg every 12 weeks |
Oral 1 mg daily |
| Effect on Endometrium |
Partial agonist; ↑ risk endometrial hyperplasia/cancer |
Antagonist; no increased endometrial risk |
N/A (suppresses hormone production) |
N/A (low estrogen state) |
| Venous Thromboembolism Risk |
Increased (DVT, PE) |
Increased (DVT, PE) |
Low risk |
Low risk |
| Common Adverse Effects |
Hot flashes, vaginal discharge, menstrual irregularities |
Hot flashes, leg cramps, edema |
Hot flashes, mood changes, decreased libido |
Hot flashes, arthralgia, fatigue |
| Serious Risks |
Endometrial cancer, thromboembolism |
Thromboembolism |
Bone loss, metabolic changes |
Osteoporosis, fractures |
| Drug Interactions |
CYP2D6 metabolism; avoid strong CYP2D6 inhibitors |
Minimal CYP interactions |
Minimal known |
Minimal CYP interactions |
| Monitoring |
VTE signs, abnormal bleeding, adherence |
VTE signs, bone density |
Bone density, metabolic profile |
Bone density, lipid profile |
| Counseling Points |
Adherence, report VTE symptoms, bleeding |
Mobility to reduce VTE risk, bone health |
Explain flare, adherence, bone health |
Adherence, bone health, report joint pain |
| Use in LCIS |
Yes – chemoprevention |
Yes – chemoprevention (postmenopausal) |
Sometimes for ovarian suppression |
No |
