Who qualifies? (High-Risk Women)
- Women with ≥1.7% 5-year risk (by Gail model) or strong family history.
- BRCA1/2 mutation carriers (though surgery is more effective for them).
- History of LCIS (lobular carcinoma in situ) or atypical hyperplasia.
- Women ≥35 years at increased lifetime risk.
Agents Used in Chemoprevention
1. SERMs (Selective Estrogen Receptor Modulators)
- Tamoxifen
- Only agent approved for both premenopausal and postmenopausal women.
- Reduces risk of ER+ breast cancer by ~50%.
- Dose: 20 mg orally daily × 5 years.
- Side effects: hot flashes, DVT/PE, endometrial cancer risk, cataracts.
- Raloxifene
- Approved for postmenopausal women only.
- Equally effective as tamoxifen in invasive breast cancer prevention, but less effective in DCIS.
- Lower risk of endometrial cancer and thromboembolic events vs tamoxifen.
- Often chosen in postmenopausal women with osteoporosis (dual benefit).
- Exemestane (25 mg daily)
- Anastrozole (1 mg daily)
- For postmenopausal high-risk women only.
- Both shown to reduce breast cancer incidence by ~50–65% in clinical trials (MAP.3, IBIS-II).
- Side effects: bone loss, arthralgias, hot flashes, cardiovascular risk.
- Need bone protection (calcium, vitamin D, bisphosphonates/denosumab if needed).
Not Used for Prevention
- Chemotherapy (anthracyclines, taxanes, etc.) → not preventive.
- Immunotherapy or HER2-targeted therapy → only for established disease.
Summary Table: Breast Cancer Chemoprevention
| Agent | Eligible Women | Risk Reduction | Key Toxicities |
|---|---|---|---|
| Tamoxifen | Pre- & postmenopausal | ↓ ER+ cancer ~50% | DVT/PE, endometrial cancer, hot flashes |
| Raloxifene | Postmenopausal | ↓ invasive cancer ~50% (less for DCIS) | Hot flashes, DVT (less than tamoxifen), no endometrial risk |
| Exemestane | Postmenopausal | ↓ cancer ~65% | Osteoporosis, arthralgia, hot flashes |
| Anastrozole | Postmenopausal | ↓ cancer ~50–60% | Bone loss, arthralgia, hypertension |
Key Clinical Note:
- SERMs are best for younger/premenopausal women (tamoxifen).
- AIs are best for postmenopausal high-risk women with no osteoporosis.
- Duration is usually 5 years.
Synonyms
Chemoprevention