GLOSSARY

Glossary

Advanced/metastatic breast cancer (a/mBC): Breast cancer that has spread to other parts of the body beyond the breast and nearby tissues.
Aromatase inhibitor (AI): An anti-cancer drug that lowers estrogen levels in the body by blocking aromatase, an enzyme involved in the production of estrogen.
Anti-hormonal therapy: term used in some countries as a synonym for endocrine therapy (see Endocrine therapy).
Biomarkers: Biological molecules (naturally occurring) found in tissues, blood or other body fluids that are a sign of a condition or disease, or describe its behavior. 
Blood test: A test where a sample of blood is taken to analyze its components, the results of which can help in the diagnosis of diseases.
Cancer: A disease where cells in the body grow uncontrollably to form tumors, often at the expense of healthy cells. Depending on how advanced the cancer is, cells can multiply in one place, nearby the original tumor, or they can spread to other parts of the body distant to the original tumor (see Metastasis).
CDK4/6: Proteins involved in cell division. In breast cancer they can be exploited by the cancer cell to contribute to uncontrolled multiplication of cancer cells.
CDK4/6 inhibitor: A type of breast cancer treatment that stops the function of the CDK4/6 proteins and helps control the growth and multiplication of cancer cells.
Circulating tumor DNA (ctDNA): DNA released from tumor cells into the blood stream. Using a liquid biopsy, this DNA can be used to test for genetic mutations, including ESR1 mutations, in the cancer.
Disease progression: The process whereby the cancer grows larger at or around the original tumor site, or spreads throughout the body (see Metastasis).
DNA: The molecule found in all cells containing the genetic code of living organisms that instructs cells to make proteins involved in living processes.
Endocrine therapy (ET): A treatment that adds, blocks the function of, or removes hormones. In breast cancer, it involves drugs that block the effects of, stop the production of, or lower the amount of estrogen in the body.
Estrogen: A hormone that plays a key role in the development and regulation of the female reproductive system and sex characteristics.
Estrogen receptor (ER): A protein inside a cell that binds the hormone estrogen.
ESR1 gene: A gene that provides instructions to the cell to produce estrogen receptors.
Gene: A part of DNA that contains the instructions for making a specific protein or set of proteins involved in living processes.
Genetic mutation: A change in the DNA sequence of a gene, which can sometimes lead to cancer.
Germline mutation: A genetic mutation that takes place in germ cells involved in the reproductive process (sperm or egg cells) (compare with Somatic mutation).
Hormone: A chemical substance produced in the body that controls and regulates the activity of certain cells or organs.
Hormone (or endocrine) receptor (HR): A protein inside a cell that binds to a specific hormone (see Estrogen receptor and Progesterone receptor).
Hormonal therapy (see Endocrine therapy).
Human Epidermal Growth Factor Receptor 2 (HER2): A protein that can promote the growth of cancer cells. In some cancers, high levels of HER2 are present and drive the progression of the disease.
Liquid biopsy: A test performed on a blood sample to look for cancer cells or pieces of DNA shed from cancer cells (see Circulating tumor DNA).
Metastasis: The process by which cancer cells spread from the place where they first formed to another part of the body distant to the original tumor site.
Progesterone: A hormone involved in the menstrual cycle, pregnancy, and embryogenesis.
Progesterone receptor (PR): a protein inside a cell that binds the hormone progesterone.
Selective Estrogen Receptor Degrader (SERD): A type of anti-cancer drug that targets and destroys estrogen receptors on cancer cells.
Selective Estrogen Receptor Modulator (SERM): A drug that acts like estrogen on some tissues but blocks the effect of estrogen on other tissues. Tamoxifen and raloxifene are SERMs. 
Somatic mutation: A genetic alteration to the DNA of a cell that can occur in any cell of the body except germ cells (sperm and egg) and can be passed to the progeny of the mutated cell during cell division (compare with Germline mutation).
Systemic therapy: a treatment that enters the bloodstream and reaches the entire body.
Tissue biopsy: A procedure in which a small sample of tissue is removed from the body for examination in a laboratory.
Treatment guidelines: Recommendations developed by experts on a local, regional, or global level to help doctors and patients make decisions about the best approaches to the treatment of diseases.
Treatment resistance: When cancer no longer responds to a treatment that was previously effective.
Tumor: An abnormal growth of cells that can be benign (non-cancerous) or malignant (cancerous).