Breast Cancer Drugs

These drugs are used to inhibit certain cancers which are characterized by the presence of oestrogen receptors on target cells. For breast cancer, they will only be given if the cancer is estrogen receptor positive.

  • SERMS (selective estrogen receptor modulators) – Tamoxifen + Toremifene + Raloxifene

This are drugs that act to modulate activity of the oestrogen receptor.
– These drugs can have both oestrogenic and anti-oestrogen effects depending on the tissue on which they are acting:
– Breast –> SERMs inhibit oestrogen receptors, so inhibit proliferation of oestrogen-dependent cancers. Used in pre-menopausal women with metastatic breast cancer or those who are high risk
– Uterus, bone and liver –> SERMs activate oestrogen receptors and so have oestrogenic effects

Side effects:
– Menopausal symptoms (fatigue, hot flushes, night sweats, mood swings)
– Abnormal vaginal bleeding or discharge
– Increased risk of VTE
– Increased risk of endometrial cancer (due to oestrogenic effects on endometrium)


  • Fulvestrant
    – This is an oestrogen receptor antagonist used to treat ER+ breast cancer
    – It is given once the breast cancer has spread to lymph nodes and breastbone
  • Aromatase inhibitors – Anastrozole + Letrozole

These inhibit the aromatase enzyme which converts testosterone to oestrogen – It is used in postmenopausal women with ER-positive breast cancer

Side effects:
Hot flushes + Osteoporosis

  • GnRH analogs – Leuprolide + Goserelin

These are analogs that bind the GnRH receptor but over time inhibit LH and FSH secretion
– This has downstream effects to decrease levels of testosterone and oestrogen
– Useful for treating prostate cancer (in men) and breast/ovarian cancer (women)
– Only given in pre-menopausal women who have ER+ or PR+ breast cancer

Side effects:

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