An AI is a type of drug that prevents an enzyme called aromatase from making estrogen. Blocking aromatase lowers the amount of estrogen in the body, which may stop the growth of cancer cells that need estrogen to grow. AIs are a type of hormone therapy used to treat HR+, HER2- breast cancer.

Cancer-free is a term used to describe a time when cancer isn’t detected anywhere in your body.

eBC is cancer that has not spread beyond the breast or beyond lymph nodes in the armpit. The stages of early breast cancer are stage 0, stage 1, stage 2A, stage 2B, and stage 3A.

There are many risk factors used to determine whether or not someone has HR+, HER2- eBC with a high risk of returning. These factors include the grade (or aggressiveness) of the cancer, a person’s genes, whether or not the cancer has spread to the lymph nodes, and the size of the tumor.

HR+ breast cancer is cancer with cells that have hormone receptors. HR+ breast cancers are more likely to respond to hormone therapy than HR-negative (HR-) breast cancers.

Hormone therapy is treatment that is used for certain types of breast cancer to add, block, or remove hormones. Hormone therapy is also referred to as endocrine therapy.

HER2 is a protein found in both healthy cells and cancer cells. HER2 plays a role in normal cell growth. In cancer, HER2 amounts are altered, which can cause the growth of cancer cells.

HER2 status means the amount of HER2 proteins found on breast cancer cells. If a lot of HER2 proteins are found, the cancer is called HER2 positive (HER2+). If no or very few HER2 proteins are found, the cancer is called HER2 negative (HER2-).

HER2- breast cancer is a type of cancer in which cancer cells have no or very low levels of the HER2 protein. HER2 can cause cancer cells to grow quickly.

Metastatic breast cancer is cancer that has spread throughout the body through blood vessels or lymph nodes to a distant location, like the bones, lungs, liver, and brain. Metastatic breast cancer is also referred to as stage 4 breast cancer. 

An initial diagnosis of stage 4 breast cancer is called de novo metastatic breast cancer.

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Referenced with permission from the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines^®) for Breast Cancer V.4.2025. © National Comprehensive Cancer Network, Inc. 2025. All rights reserved. Accessed April 17, 2025. To view the most recent and complete version of the guideline, go online to NCCN.org.

NCCN makes no warranties of any kind whatsoever regarding their content, use, or application and disclaims any responsibility for their application or use in any way.

Postmenopausal describes someone who has gone through menopause. This means that you haven’t had a menstrual period for more than 12 months in a row.

Premenopausal describes someone who has not gone through menopause and still has menstrual periods.