“The USPSTF recommends that the selective estrogen receptor modulators tamoxifen and raloxifene be offered to women at high risk for breast cancer and low risk for adverse medication effects (B recommendation).
This reduces the incidence of invasive breast cancer by 7–9 events per 1000 women over 5 years.
Tamoxifen has been shown to be more beneficial than raloxifene.
Potential harms include an increase of 4–7 events of venous thromboembolism per 1000 women over 5 years. Tamoxifen increases the risk more than raloxifene. Tamoxifen also reduces bone fractures but increases the incidence of endometrial cancer, leg cramps, bladder control issues, vasomotor symptoms, and vaginal dryness, itching, and discharge.” ABFM
Mechanism of Action of Tamoxifen
“Selectively binds to estrogen receptors, producing estrogenic and anti-estrogenic effects (estrogen receptor modulator);
estrogen antagonist in breast cancer cells, preventing tumor growth;
estrogen agonist in the hypothalamus of premenopausal women, increasing gonadotropins and inducing ovulation;
exact mechanism of action in McCune-Albright syndrome unknown.” Epocrates.
Mechanism of Action of Raloxifene
Selectively binds to estrogen receptors, producing estrogenic and anti-estrogenic effects (estrogen receptor modulator);
estrogen antagonist in breast and uterine tissue, inhibiting breast epithelium proliferation and decreasing endometrial hyperplasia risk.
estrogen agonist in bone, decreases bone resorption and turnover;
” Epocrates.
Reference
USPSTF