What Does That Mean? — Glossary

The ABC’s of breast cancer — A glossary of the breast cancer terms you have questions about. We’re always updating this list with more decoded terms, so be sure to check back!

If there’s something you want to see on here, reach out to jasmine@rethinkbreastcancer.com


Adjuvant therapy is a secondary method of treatment that is performed after the primary treatment method to lower the risk of the cancer returning. Examples include: chemotherapy and radiation therapy. 

Advanced Breast Cancer

Advanced breast cancer is another term used to describe metastatic breast cancer (see definition). It is not a different type of breast cancer. Rather, it is the most advanced stage (stage IV) of breast cancer.

Advanced Care Planning

Advanced care planning is the process of deciding ahead of time the kind of health and personal care you want in the future if you were to reach the point where you can no longer speak for yourself.

Adverse Events

Adverse events are also known as side effects, an adverse event is an unexpected or dangerous reaction to a treatment or medication. They are captured in the clinical trial and should be reported as part of the safety profile of the treatment.

Axillary Lymph Node Dissection

Lymph nodes are small glands located in the underarm area. When someone’s lymph nodes are removed it’s called an axillary lymph node dissection. This surgery is usually combined with a mastectomy (see “mastectomy” definition). 


Benign is an adjective used to describe a tumour that is non-cancerous.    


Also known as a molecular marker, a biomarker can be proteins, gene mutations, gene rearrangements, extra copies of genes, missing genes or other molecules that can affect how cancer cells grow, multiply, die and respond to other compounds in the body. Biomarkers can be found in the blood, tissue and other body fluids and can be used to help identify to which treatment the cancer may respond. 


A biopsy is the removal of tissues and/or cells to be examined by a pathologist (see “pathology” definition). This is usually the only way to tell for certain if a lump in your breast is benign or cancerous.

Blinded Study

A blinded study is a type of study in which it is not known what type of treatment the participant is given. In a single-blinded study, the patients do not know. In a double-blinded study, both patients and physicians do not know.  (An open-label study is the opposite of a blinded study)

BRCA Genes

There are two BRCA genes: BRCA 1 and BRCA 2. Everyone has them and they protect us from getting breast and ovarian cancers. However, BRCA gene mutations can be inherited, which actually increase a person’s risk of developing these cancers, as well as prostate cancer. Women and those assigned female at birth with BRCA gene mutations have a 40%-85% chance of developing breast cancer.

Breast Cancer

Breast cancer is cancer (the overproduction of cells) produced in the breast tissue. The majority of people diagnosed with breast cancer have random mutations arising during DNA replication in normal, noncancerous stem cells.


A “breastie” is a term used in the breast cancer community to describe your breast cancer best friend, combining breast cancer + best friend = breastie!


A carcinoma is a type of cancer that begins in skin cells or in the tissue lining organs like the liver or kidneys.     

CDK Inhibitors

A CDK (cyclin-dependent kinase) inhibitor is any chemical that inhibits the function of CDKs. They are used to treat cancers by preventing the over proliferation of cancer cells. They are also called AT7519M. Right now there are many breakthrough breast cancer CDK inhibitors coming to market.


Chemotherapy (or chemo for short) is a type of cancer treatment that that stops cancer cells from dividing or kills them altogether. Chemo has many forms, like: an injection, a pill, or infusion.

Clinical Trial

Clinical trials are a way to test new medical advancements (treatment, prevention, screening, diagnosis, etc.) in humans before making them readily available to all. They are an experiment or research study to test a new idea.  It could evaluate the safety of a new treatment or how well it works. Also, cancer screening, prevention and diagnosis are all studied in clinical trials. 

Complete Response

Complete response refers to the disappearance of all signs of cancer in response to treatment.  It may not mean the cancer has been cured.  Also knows as complete remission.


DCIS (ductal carcinoma in situ), occurs when abnormal cells are found in the lining of the breast duct, but have not spread to other parts of the breast tissue (non-invasive).   

De Novo

De Novo is a term, often associated with metastatic breast cancer (see definition), to describe a person’s first occurrence of cancer.  

EBC (Early Breast Cancer)

EBC is breast cancer that is contained in the breast. It has been detected before it’s spread to the lymph nodes or the armpit. 

Event Free Survival (EFS)

Event-free survival (EFS) is a potential “surrogate” endpoint in clinical trials. It refers to the time from randomization in a clinical trial to any occurrence that would end the patient’s participation in the study.


An endpoint is an event or outcome that can be objectively measured in a clinical trial.  Examples include survival, improvement in quality of life, relief of symptoms and disappearance of the tumour.

End of Life Care

End of life care is treatment that focuses on improving a patient’s quality life after their illness has become terminal and/or incurable.   

Estrogen Receptor Positive

Estrogen Receptor Positive (ER+) is used to describe breast cancer cells that may receive signals from the hormone estrogen to promote their growth.   


FEC is a chemotherapy treatment that combines three chemotherapy drugs: 5 fluorouracil, epirubicin, and cyclophosphamide – which help stop cancer cells from growing or kill them altogether.   


Genes hold a person’s DNA and are the basic function of hereditary.     

Genetic Counselling

Genetic counselling is a series of conversations between a trained health professional and a person who is concerned about their risk of inheriting a disease.  

Germline testing

Germline testing (also known as genetic testing), usually occurs after genetic counseling to determine a persons familial risk of cancer.   

Genetic testing 

Genetic testing examines cells or tissue for inherited changes in the genes, chromosomes or proteins that may have harmful, beneficial, neutral or no effect on a person’s health. Genetic tests are designed to detects a single gene mutation (such as BRCA1), while genomic testing looks at all of the genes and how they interact with each other. 


Genomics is when a person’s (or organism’s) complete set of DNA, including all of its genes, is studied. This helps to understand how the genes interact with each other and how diseases, including cancer, form and can lead to new ways to diagnose, treat and prevent disease. 

Genomic testing 

Genomic testing examines the complete set of DNA, including all of its genes, how they interact with each other and how it affects a person’s health. Genomic testing can sometimes identify treatments that target the specific type of cancer and prevent normal cells from being harmed. 

Germline mutation 

A germline mutation is a gene change or variant in the body’s cells – egg cells in those assigned female at birth and sperm cells in those assigned male at birth – that are incorporated into all the DNA cells when they are passed from parents to their children at the time of conception. Cancers caused by germline mutations are called inherited or hereditary cancers.  


If you’re HER2-positive, your cancer cells make an excess amount of the HER2 protein. Originally made to control a breast cell’s growth, when the HER2 protein doesn’t work properly, breast cells can overproduce. This breast cancer tends to be aggressive, but there have been important breakthroughs in treatment.

High Risk

High risk refers to the certain factors that increase a person’s risk of developing breast cancer – more so than just the average person. They include: genetic, familial, and personal factors. 

Hormonal Therapy

Hormone Therapy (HT) uses drugs to block the production of estrogen and other female hormones that promote the growth of certain kinds of cancer cells after surgery.  


A program that gives special care to people who are near the end of life and have stopped treatment to cure or control their disease. Hospice offers physical, emotional, social, and spiritual support for patients and their families. The main goal of hospice care is to control pain and other symptoms of illness so patients can be as comfortable and alert as possible. It is usually given at home, but may also be given in a hospice center, hospital, or nursing home.

IDC (Invasive Ductal Carcinoma)

IDC (or invasive ductal carcinoma) is a type of breast cancer that starts in the milk ducts of the breast and has spread to surrounding breast tissues. It is the most common type of breast cancer.  

ILC (Invasive Lobular Carcinoma)

ILC (or invasive lobular carcinoma) is a type of breast cancer that starts in the milk-producing lobules of the breast and has spread to surrounding breast tissue. It is the second most common type of breast cancer, next to IDC (invasive ductal carcinoma).


Immunotherapy is a form of cancer treatment the body’s immune system to fight cancer by boosting it with treatments and substances that improve the body’s natural response to illness. 

Invasive Breast Cancer

Breast cancer becomes invasive when it has moved from where it originally started to now affect surrounding normal tissues. The most common form is invasive ductal carcinoma (see definition).


Investigational refers to a drug or procedure which has been approved to be studied in human subjects in a clinical trial.  It can include a new drug, dose, combination or a way to administer.

Locally Advanced

Locally advanced is a term to describe cancer that has spread from its original location to surrounding tissue or lymph nodes.   


A lumpectomy is a breast cancer surgery that removes the cancer and part of the abnormal surrounding tissue, but not the entire breast.   


Lymphedema is a common side effect of cancer treatment condition where the lymph nodes produce excess fluid, causing them to swell.   


Malignant is an adjective used to describe a tumour that is cancerous. They can destroy and spread to surrounding tissues.   


A mammogram is a form of breast cancer screening where an x-ray is taken of the breast.    


A mastectomy is a surgery done to remove part or all of the breast that has cancer.     


Menopause occurs when a menstruating person stops having menstrual periods because their ovaries no longer produce hormones. Natural menopause usually occurs around the age of 50. Sometimes, a side effect of cancer treatment for young people is early menopause.


When cancer cells metastasize, they spread to other parts of the body.    

Metastatic Breast Cancer

Metastatic breast cancer (MBC) is cancer that’s spread to other parts of the body. When breast cancer is found outside the breast, it is still made up of breast cancer cells and still considered breast cancer.

NED (“No Evidence of Disease”)

NED (or “no evidence of disease”) is a term used when tests show no presence of cancer cells in someone who was previously being treated for cancer. NED has replaced the term remission because it is more accurate.

Neo-adjuvant Therapy

Neo-adjuvant therapy usually occurs before the primary cancer treatment (ie/ surgery). It includes chemotherapy, radiation therapy, and hormone therapy used to shrink the cancerous tumour. 


Chemotherapy treatment can often kill non-cancerous cells in the body in addition to the cancerous ones. Neutropenia is often a side effect that occurs when the body’s white blood cell count is too low because of this. 

Observational Study

An observational study is a type of study in which researchers observe certain outcomes in individuals. There is no effort to shape the results (e.g. no treatment is given).


An oncologist is a doctor who specializes in diagnosing and treating cancer with chemotherapy or in some cases immunotherapy.  


An oophorectomy is surgery to remove one or both of a woman’s ovaries.     

Overall Survival

Overall survival (OS) represents the length of time from either the date of diagnosis or the start of treatment for a disease, such as breast cancer, that patients are still alive.  In clinical trial data, OS is reported as the participants’ average length of time.

Palliative Care

Palliative care given specifically to people suffering from a life-long or life-threatening illness. This kind of care focuses on improving patients’ quality of life (see definition), focusing on all aspects of having an illness: physical, psychological, spiritual, etc.

Partial Response

Partial response refers to a decrease in the tumour size or the extent of cancer in the body. Also known as partial remission.


Pathology is the study of diseases by examining tissues under a microscope.    

Peer Support

Peer support connects people living with cancer or people with other illnesses to others who have gone through it. Peer support is not based on psychiatric models and diagnostic criteria.


Phase refers to the stage of the clinical trial. Pre-clinical phase trials test potential treatments before it is tested in humans. Phase 1 trials study the potential and how safe the new treatment is in a small group of people. Phase 2 trials test the treatment in larger groups of people to show the benefit and optimal dose.  Phase 3 trials test the new treatment against the current standard of care. Phase 4, also known as real-word evidence, is the data collected once the treatment is approved and patients are using it.


Placebo is a “pretend” treatment that does not contain any active medication. It is given as a control to evaluate a new treatment in a clinical trial. It is often in the form of a tablet, injection or infusion that contains harmless ingredients.


Progesterone is a hormone that plays a role in the menstrual cycle and pregnancy. If the breast cancer is Progesterone receptor-positive (PR+), that means its cells may receive signals from progesterone that promote their growth. 


A prognosis is typically given by a doctor. It indicates the likely course that a disease or illness will take, including the chances of it recurring.  

Progression-free survival

Progression-free survival (PFS) represents the length of time during and after the treatment of a disease such as breast cancer that patients live with the disease, but it does not get worse or progress. In clinical trial data, PFS is reported as the participants’ average length of time.

Quality of Life (QOL)

Cancer treatments and clinical trials are often concerned with improving patients’ quality of life (QOL). This refers to their overall enjoyment of life and their wellbeing.   

Radiation Therapy

Radiation Therapy uses high-energy X-rays to destroy any cancer cells that may remain in the breast after surgery. This reduces the chance of recurrence.  

Randomized Clinical Trial

Randomized clinical trial is a way to fairly compare the effects of different treatments by dividing clinical trial participants by chance. At the time of the trial, it is not known which treatment is best. 

Real-world Evidence

Real-world evidence (RWE) is the clinical evidence related to the real-world data collected once the drug or treatment is approved, marketed and used by patients outside of a controlled clinical trial setting. It can assess the potential benefits and risks of a treatment.  Real-world data can come from a variety of sources, including electronic medical record, disease or product registries and patient-reported data.

Response Rate

Response rate refers to the percentage of people in a clinical trial whose cancer shrinks or disappears in response to the treatment.

Rethink Young Women’s Network (RYWN)

Rethink Young Women’s Network (RYWN) is a safe, private community of young women that have personal experience with breast cancer at any stage. It is a place to get support, have your questions answered, connect with other breasties and engage in meaningful conversations with others who get what you’re going through.


Situ is used to describe a tumour, cancer, etc. which is confined to where it first started. In other words, it hasn’t spread. For example, ductal carcinoma in situ, is a breast cancer found in the milk ducts which has not spread to other tissues or parts of the body.

Somatic mutation 

A somatic mutation is a change in a person’s DNA, most often caused by tobacco use, exposure to ultraviolet light or radiation, viruses, chemicals exposure and aging. They are the most common cause of cancer (but don’t always cause cancer). The mutation can occur in any of the body’s cells excepts the germ cells (egg cells in those assigned female at birth and sperm cells in those assigned male at birth) and therefore are not passed onto children.  


Stage is a term used to diagnose how advanced breast cancer is. It’s determined by tumour size, the number of lymph nodes affected, and whether it has spread to other tissues and/or parts of the body.

Statistically Significant

Statistically significant is a mathematical term that signifies when a difference is greater than what would be expected to happen by chance alone.


The state of being a survivor. Survivorship refers to a community of individuals who are living their best lives post-cancer and the resources and tools they can use to do so.   


Tamoxifen is a cancer drug used to treat and/or prevent certain types of breast cancer. It’s often used to treat ductal carcinoma in situ (see definition) or to prevent breast cancer in those who are high risk (see definition) for developing the disease.


The term “thriver” is used in the metastatic breast cancer (MBC) community to differentiate from Survivor. Survivor can imply that cancer is cured and they are no longer living with the disease. Those with MBC live with their cancer but can be thriving.


A tumour is a group of abnormal cells that forms when cells divide and multiply too quickly or don’t die when they should. Tumours can be benign (non-cancerous) or malignant (cancerous).


An ultrasound is a breast cancer screening method that uses sound waves to examine the tissues. It tends to be a better screening method for young women or those assigned female at birth under 40, who’s breast density prevents tissues from showing up properly on a mammogram.

Values (patient values)

Patient values refers to what patients value when it comes to cancer treatment and how they measure quality of life (see definition).  

Washout Period

Washout period is a term used to describe the process where a patient in a clinical trial (see definition) is taken off a drug in order to give it time to leave their system.  


Xeloda is a cancer treatment often used for stage III colon cancer patients. However, it’s also often used to treat metastatic breast cancer (see definition) in those whose situation hasn’t improved with the use of any other anti-cancer drugs. 

Young People with Breast Cancer 

The Rethink definition of young refers to people at a specific stage of life when there are demands on family, friends, careers, education and fertility. Most of these people are pre-menopausal. Rethink believes that the advocacy work we do with young people helps to improve access and create change for all.


Zoladex is a hormone therapy drug used to treat estrogen receptor-positive breast cancer (see definition) by halting the production of estrogen in the ovaries.   

Have a term you want us to explain and add to this list? Please email jasmine@rethinkbreastcancer.com
For more terms and definitions, check out this online glossary.

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