Estrogen and progesterone are female hormones produced in the body. Some breast cancer cells need estrogen and/or progesterone to grow.

When these hormones attach to special proteins called hormone receptors, the cancer cells with these receptors grow.

Hormone therapies slow or stop the growth of hormone receptor-positive tumors by preventing the cancer cells from getting the hormones they need to grow.

All breast cancers are tested to see if they have hormone receptors. Breast cancers that have a lot of hormone receptors are hormone receptor-positive and can be treated with hormone therapies.

Hormone therapy drugs slow or stop the growth of hormone receptor-positive breast cancers.