Does hormone therapy work for all breast cancers?

No. Hormone therapy only works for breast cancers that are hormone receptor positive.

To know whether hormone therapy could help, doctors test tumor tissue for proteins called hormone receptors — estrogen receptors (ERs) and progesterone receptors (PRs). If the cancer cells contain these receptors, the cancer is called hormone receptor positive (HR positive). Tumors that lack them (HR negative) do not respond to hormone therapy.

About 80% of people diagnosed with breast cancer have HR-positive cancers, so hormone therapy is an option for many people, but not everyone.

Hormone therapy works by blocking the body's ability to make hormones or by blocking the effects of hormones on breast cancer cells. If your cancer is HR negative, your care team will recommend other treatments that fit your situation.