Hormones are substances produced naturally in the body. They act as chemical messengers and help control the activity of cells and organs. Hormonal therapies are drugs that interfere with the way hormones are made or how they work in the body.
Many breast cancers rely on the hormone oestrogen to grow. This is called oestrogen-receptor positive (ER positive) breast cancer. Toremifene blocks oestrogen from reaching the cancer cells. This means the cancer may grow more slowly or stop growing altogether.