Hormone therapy can reach cancer cells almost anywhere in the body and not just in the breast. It’s recommended for women with tumors that are hormone receptor-positive. It does not help women whose tumors don’t have hormone receptors (these tumors are called hormone receptor-negative).
Hormone therapy is often used after surgery (as adjuvant therapy) to help reduce the risk of the cancer coming back. Sometimes it is started before surgery (as neoadjuvant therapy).
It is usually taken for at least 5 years. Treatment longer than 5 years might be offered to women whose cancers have a higher chance of coming back. A test called the Breast Cancer Index might be used to help decide if a woman will benefit from more than 5 years of hormone therapy.
Hormone therapy can also be used to treat cancer that has come back after treatment or that has spread to other parts of the body.
How does hormone therapy work?
About 2 out of 3 breast cancers are hormone receptor-positive. Their cells have receptors (proteins) for estrogen (ER-positive cancers) and/or progesterone (PR-positive cancers) which help the cancer cells grow and spread.
There are several types of hormone therapy for breast cancer. Most types of hormone therapy either lower estrogen levels in the body or stop estrogen from helping breast cancer cells grow.
Why it’s done
Hormone therapy for breast cancer is only used to treat cancers that are hormone sensitive (hormone receptor positive breast cancers).
Doctors refer to these cancers as estrogen receptor positive (ER positive) or progesterone receptor positive (PR positive). This means that these breast cancers are fueled by the natural hormones estrogen or progesterone.
A doctor who specializes in analyzing blood and body tissue (pathologist) determines if your cancer is ER positive or PR positive by analyzing a sample of your cancer cells to see if they have receptors for estrogen or progesterone.
Hormone therapy for breast cancer can help to:
- Prevent cancer from coming back
- Decrease the risk of cancer developing in other breast tissue
- Slow or stop the growth of cancer that has spread
- Reduce the size of a tumor prior to surgery
