Glossary

A type of study that combines the results from multiple individual studies. This can give more reliable results than a single study, and can also highlight interesting differences between the individual studies.

The original cancer. Cells from the primary cancer may break away and be carried to other parts of the body, where secondary cancers form.

A type of study that combines the results from multiple individual studies. This can give more reliable results than a single study. It can only be used if the individual studies used the same design and similar populations.

Occurs when abnormal cells in the ovary, fallopian tube or peritoneum grow in an uncontrolled way.

A type of breast cancer that is not oestrogen-receptor-positive.

A type of breast cancer in which the breast cancer cells have proteins on their surface (oestrogen receptors) that allow them to use the hormone oestrogen to grow. About 80% of all breast cancers are ER+.

The main female sex hormone, produced mostly by the ovaries. Oestrogen regulates the menstrual cycle and prepares the breasts for milk production.

The likelihood that breast cancer will develop in the presence of a particular risk factor compared with the likelihood in the absence of that risk factor. For example, an odds ratio of 2 for a risk factor means that women with that risk factor have twice the chance of developing breast cancer as other women.

The likelihood that something will occur – for example, that a woman will develop breast cancer.

A change in the DNA sequence of a gene. Mutations can occur in a person’s DNA during their lifetime, or can be inherited from their parents.

The factor is likely to be associated with increased or decreased risk of breast cancer, but the evidence is not as strong as for convincing.

A process that takes a picture of the breast using low-energy X-rays to detect breast cancer.

A type of breast cancer, based on particular proteins that occur on the surface of the breast cells.

Cancer that develops in the milk-producing glands of the breast.

The chance of developing cancer during your lifetime. For example, a woman with no known risk factors for breast cancer has a lifetime risk of developing breast cancer of about 12%.

Risk factors relating to a person’s lifestyle – for example, diet, alcohol consumption, smoking, weight gain and weight loss, obesity, and level of physical activity.

The evidence is too limited to determine the likelihood of an association with increased or decreased risk of breast cancer.

International Agency for Research on Cancer – the cancer agency of the World Health Organization.

Therapy that supplies the body with hormones that it is no longer able to produce; it is used to relieve menopausal symptoms.

Aunts, uncles, grandparents, grandchildren, nieces, nephews and half-siblings.

A not-for profit organisation that unites a network of cancer prevention charities, including the American Institute for Cancer Research in the United States.

Genes (and proteins) that occur in our bodies that stop cells growing in an uncontrolled way and developing into cancer. They often work by repairing mistakes that occur in our DNA.

An abnormal growth of tissue. It may be localised (benign) or invade adjacent tissues (malignant) or distant tissues (metastatic).

A type of breast cancer in which the breast cancer cells do not have oestrogen receptors or progesterone receptors, and do not produce too much of the HER2 protein. Many breast cancers associated with the BRCA1 gene are triple negative.

A collection of cells that make up each piece (or organ) of the body.

A type of review of the literature that uses systematic methods to critically assess the relevant research on a topic. The aim is to thoroughly summarise the current evidence on that topic.

The evidence is indicative of an association between the factor and increased or decreased risk of breast cancer, but there is not sufficiently strong evidence to be more certain.

A change in the genetic material (DNA) at a single location in the DNA.

A substance made in the body that affects how your body works. Some hormones control growth; others control reproduction. Hormones travel around the body in the bloodstream.

A malignant tumour (a cancer) that starts in connective tissue.

A substance or condition that increases a person’s chances of getting a particular type of cancer.

A measure of risk that compares the absolute risk of developing a disease (such as cancer) in a group of people who have a particular risk factor with the absolute risk in a group of people who do not have that risk factor. For example, a certain gene mutation might double the risk of breast cancer – the relative risk is 2 for that risk factor.

In studies of cancer risk, recall bias occurs when people in the study cannot completely or accurately remember events or experiences in the past. This can lead to misleading results.

In studies of cancer risk, recall bias occurs when people in the study cannot completely or accurately remember events or experiences in the past. This can lead to misleading results.

The use of radiation, usually X-rays or gamma-rays, to kill tumour cells, or injure them so that they cannot grow or multiply.

A type of breast cancer in which the breast cancer cells have proteins on their surface (progesterone receptors) that allow them to use the hormone progesterone to grow.

A sex hormone, produced by the ovaries, that plays an important role in the menstrual cycle and in maintaining the early stage of pregnancy.

A term for diseases in which abnormal cells divide without control. Cancer cells can invade nearby tissues, and can spread through the bloodstream and lymphatic system to other parts of the body.

A range of values surrounding the true value. Confidence intervals are used in statistical studies that look at a sample of people to draw conclusions about the whole population. A 95% confidence interval means that we can be 95% confident that the true value falls within this range.

A type of study design to find out whether a particular factor is associated with the risk of cancer. A group (cohort) of people with a particular risk factor for cancer is followed over a period and compared with a matched group without that risk factor.

There is compelling and consistent evidence that the factor increases or decreases the risk of breast cancer.

A threadlike structure found in the nucleus of all body cells (except red blood cells) made up of genes.

The use of medicines that kill or slow cell growth to treat cancer.

The building blocks of the body. A human body is made of millions of cells, which are adapted for different functions. Cells can reproduce themselves exactly, unless they are abnormal or damaged, as are cancer cells.

A type of study design to find out whether a particular factor is associated with the risk of cancer. A group of people with cancer (the ‘cases’) is compared with a matched group without cancer (the ‘controls’) to look at the differences between the 2 groups (eg level of alcohol consumption).

A person who has a single copy of a particular variation of a gene in their genetic makeup (rather than 2 copies of that variation). For many genes, this means that the gene does not cause any symptoms. However, the carrier of the gene can pass it on to their children.

A substance known to cause and/or promote cancer. Carcinogens can be created by humans (eg cigarette smoke) or can be present naturally in the environment (eg ultraviolet radiation from the sun).

In studies of risk factors that are associated with cancer, a confounder is a different factor that is also associated with risk of cancer. Confounders can lead to the wrong conclusions about the cause of cancer if they are not taken into account. For example, if the risk factor being studied is consumption of sugar, women who eat a lot of sugar might also have more body fat than average – body fat is a confounder in this case.

Breast Cancer susceptibility 2 gene. Women who have a mutation in the BRCA2 gene have an increased risk of breast cancer. The BRCA2 gene produces a protein that helps to repair DNA when it is damaged. When the gene is mutated, the protein stops working.

Breast Cancer susceptibility 1 gene. Women who have a mutation in the BRCA1 gene have an increased risk of breast cancer. The BRCA1 gene produces a protein that helps to repair DNA when it is damaged. When the gene is mutated, the protein stops working.

A measure of body fatness. BMI is calculated by dividing your weight (in kilograms) by the square of your height (in metres squared). For example, a person who weighs 65 kg and is 170 cm tall has a BMI of 22.5 (= 65/1.7²).

Removal of a small amount of tissue from the body for examination under a microscope, to help diagnose a disease.

Not cancerous. Benign cells are not able to spread like cancer cells.

The chance of developing a disease (such as cancer) during a given time. For example, the absolute risk of a woman developing breast cancer by the age of 85 years is 1 in 8.

Cancer of the breast. Breast cancer is most common in women, but also affects a small number of men. A term for diseases in which abnormal cells divide without control. Cancer cells can invade nearby tissues, and can spread through the bloodstream and lymphatic system to other parts of the body.

The evidence is too limited to determine the likelihood of an association with increased or decreased risk of breast cancer.

Indicates that a condition can be inherited through the generations of a family through one or more genes.

For a particular gene, homozygous means that each cell in the body contains two identical versions of the gene – inherited from the mother and the father.

For a particular gene, heterozygous means that each cell in the body contains two different versions of the gene – one inherited from the mother and one from the father. This is usually one copy of the normal gene and one copy of a mutated form of the gene.

A type of breast cancer in which a protein on the surface of breast cells (human epidermal growth factor receptor 2) is made in larger amounts than usual. This can make the cells grow in an uncontrolled way and lead to breast cancer.

Cells in the body that will become sperm cells or egg cells. The genetic material in these cells can be passed on to the next generation.

The elements of a cell that carry instructions on how the cell should grow and function. Each person has a set of many thousands of genes inherited from both parents. This set is found in every cell of the body.

A disease that is caused by defects in genes and is passed from one generation to the next.

Parents, brothers, sisters and children.

Occurrence of cancer within the same family. This might be because of inheritance of genes. However, members of a family often also have similar lifestyles (eg diet, exercise), meaning that they can share lifestyle risk factors for breast cancer.

A measure of how likely a person is to develop a disease or a side effect.

There is consistent evidence from good quality studies to show that this factor neither increases nor decreases the risk of breast cancer.

The observations and experimental results that support a hypothesis.

The cells that make up the internal and external surfaces of the body (eg skin, inside of lungs, surface of ovaries).

The study of the patterns and causes of health and disease in populations, and the application of this study to improve health.

Cancer that develops in the milk ducts of the breast.

A situation where an increasing dose of something, or exposure to something, has a greater effect. For example, there is a dose–response relationship between alcohol consumption and the risk of breast cancer. The more a woman drinks, the higher her risk of breast cancer.

Deoxyribonucleic acid, the genetic material found in human cells that makes up the genes.

The identification and naming of a person’s disease.