Hormone-Resistant Breast Cancer

Hormone-resistant breast cancer is breast cancer that has stopped responding to hormonal treatment. Roughly 70% of breast cancers are hormone receptor–positive (HR+), either estrogen receptor–positive (ER+) or progesterone receptor–positive (PR+), meaning that their growth is fueled by estrogen or progesterone, respectively. Treatment for these HR+ breast cancers work by lowering the levels of estrogen or progesterone in the body, blocking the hormones from attaching to the breast cancer cells.

About 50% to 60% of early-stage HR+ breast cancers become resistant to hormonal therapy, that is, they stop responding to the therapy. Most all advanced-stage HR+ breast cancers become hormone-resistant at some point.

Treatment options for hormone-resistant breast cancer include:

  • If premenopausal: with progression on tamoxifen:
    • Ovarian ablation or suppression + a nonsteroidal aromatase inhibitor
    • Ovarian ablation or suppression + a steroidal aromatase inactivator
    • Ovarian suppression + any of the options for postmenopausal women
  • If postmenopausal:
    • Ovarian ablation or suppression + a nonsteroidal aromatase inhibitor
    • Ovarian ablation or suppression + a steroidal aromatase inactivator
    • Fulvestrant
    • Everolimus + fulvestrant
    • Palbociclib + an aromatase inhibitor
    • Palbociclib + fulvestrant
    • Ribociclib + aromatase inhibitor
    • Abemaciclib + fulvestrant
    • Megestrol
    • Fluoxymesterone
    • Abemiciclib