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Understanding Cancer Research Terms

The Glossary for Nonscientists 

Get more out of American Cancer Society studies on epidemiology, statistics, genetics, and other complex topics with this glossary of terms used in cancer research, explained in plain language for nonscientists. 

5-year cancer survival rate: The percentage of people with the same type and stage of cancer who are alive at least 5 years after diagnosis. A 5-year survival rate does not mean that people can’t live more than 5 years, nor does it mean that those who live at least 5 years are cured. A high percentage for a 5-year survival rate may mean treatment works well for most people. A low percentage for a 5-year survival rate may mean treatments aren’t very effective.

138% of Federal poverty line: The maximum yearly income the Affordable Care Act (ACA) supports for people to qualify for Medicaid. In 2022 for example, the federal poverty line (FPL) for a family of 3 was $23,030. The ACA provides financial incentives that allow parents in a family of 3 to have a yearly income up to 138% of the FPL, which was $31,781 [$23,030 + (38% of $23,030)], and still qualify for Medicaid.

In 2022, 37 states had 138% FPL as their Medicaid income eligibility limit. But states can set their own income limits for Medicaid eligibility, and they can be below, at, or above the FPL. In 2022, Washington, DC had the most generous Medicaid income eligibility limit—221% of the FPL—for a family of 3. Texas had the least generous—16% of the FPL. 

Abstinence: The practice of choosing not to do a certain behavior or give into a desire or addiction, such as using tobacco or alcohol.

Advanced cancer: A general term describing the late stages of cancer, when the disease has spread from where it started (the primary site) to other parts of the body. When the cancer has spread only to the nearby areas, it is called locally advanced cancer. If it has spread to distant parts of the body, it is called metastatic cancer. See also metastasis, metastasize.

African American/Black: People in the United States who can trace their lineage to Africa. Some Black people do not identify as African American. The Black lineage contains many histories, cultures, and experiences, including Afro-Caribbean and Afro-Latino populations.

Age-adjusted cancer death rates: A cancer death rate that has been adjusted with a math calculation to allow for differences in age so that 2 populations can be more directly compared. See also Understanding the Cancer Death Rate. 

American Indian and Alaska Native (AIAN): A person with origins in any of the First Peoples in North, Central, and South America who maintains tribal affiliation or community attachment. These include Navajo, Blackfeet, Inupiat, Yup’ik, and Central and South American Indian groups. The AIAN is a federally recognized tribal entity with certain rights of self-government and are entitled to receive US federal benefits, services, and protections.

Aneuploid/Aneuploidy: Cells that have either more, or less, than the normal 23 pairs of chromosomes. Most cancer cells are aneuploid. It’s rare for a normal cell to have aneuploidy. See also chromosome, diploid, and ploidy. 

Apoptosis: Programmed cell death. Apoptosis is controlled by genes that cause cells to die at certain times, for example, when DNA is damaged. This type of cell death is different from the process of cell death by decay. Some drugs used to treat cancer cause apoptosis.

Asian American: A broad term that refers to a person having origins in the Far East, Southeast Asia, or the Indian subcontinent. This group includes, but is not limited to, Asian Indians, Cambodians, Chinese, Filipinos, Hmong, Japanese, Koreans, Pakistanis, Thai, and Vietnamese.

Behavioral research: Research into what motivates people to act the way they do. The results of such research can be used to help encourage people to adopt healthy lifestyles and follow life-saving screening and treatment guidelines.

Bioinformatics: Bioinformatics has been called a marriage of biology and information technology. This scientific, interdisciplinary field uses computer technology, mathematics and statistical methods, physics, engineering, and biology to make super large sets of complex life-sciences data more understandable and useful.

Scientists with specialization in bioinformatics use tools of computation and analysis to retrieve, analyze, manipulate, and interpret the massive, unprecedented amounts of diverse, and complex data (described as "big data") that are now available due to advances in systems and techniques like next-generation sequencing. 

Bioinformatics comprises 3 components:

  • Creation of databases
  • Development of algorithms and statistics
  • Analysis of data and interpretation

Bioinformatics is part of computational biology.

Biologic age/biological aging (also known as epigenetic age/epigenetic aging): Biological aging is a gradual and progressive process of aging to the body’s cells driven by epigenetic changes to the DNA. Those changes to the DNA result from such things as:

  • The accumulation of damage to your body’s cells caused by the natural wear of your body, as well as your lifestyle (like how you eat, sleep, and exercise)

  • Your life experiences (like where you live and what kind of work you do) 

  • Your exposure to harmful environments (like cigarette smoke and air pollution)

Increased biological age increases the risk for developing cancer and other age-related diseases. Your biological age can be younger or older than your chronological age, which increases with each birthday.

Biomarker (also called molecular marker or signature molecule): A measurable molecular (such as a protein), genetic, chemical, or physical characteristic in the blood or other bodily fluids, such as sweat and tears, that is a sign of a normal or abnormal process or of a health condition or disease. Biomarkers can help in early diagnosis, disease prevention, drug target identification, and drug response. The US Food and Drug Administration (FDA) classifies 7 categories of biomarkers: susceptibility biomarkers, diagnostic biomarkers, response biomarkers, safety biomarkers, prognostic biomarkers, monitoring biomarkers, and predictive biomarkers.

Biorepository: A facility that collects, catalogs, and stores samples of biological materials. The ACS Cancer Prevention Studies biorepository includes blood, urine, buccal cells (from the inside of the cheek), cancer tissue, and stool.

Biospecimen: A sample of a biological material, such as blood, urine, tissue, cells, or stool collected from participants for research.

BRCA1: A gene which, when damaged (mutated), puts a person at higher risk of developing breast, ovarian, prostate, and other types of cancer, compared to people who do not have the genetic mutation. See also gene, mutation.

BRCA2: A gene which, when damaged (mutated), puts a person at higher risk of developing breast, ovarian, prostate, and other types of cancer, compared to people who do not have the genetic mutation. See also gene, mutation.

Breast cancer genes: The genes most commonly mutated in hereditary breast cancer are the breast cancer 1 (BRCA1) and breast cancer 2 (BRCA2) genes.

C-reactive protein (CRP): The liver releases CRP into the bloodstream in response to inflammation. Blood levels of CRP increase with inflammatory conditions like severe tissue damage from injury, rheumatoid arthritis, some heart diseases, infection, and progressive cancer. 

Cancer burden: How the number of cancer cases and results of cancer affect a country, community, family, or one person. For example, the cancer burden for a specific person depends on their risk factors for cancer, how well they manage their modifiable risk factors, how closely they follow the recommended cancer screening schedule, if they develop cancer, and their access to high-quality cancer treatment. See What Is Cancer Control?

The national or a state's cancer burden is measured by:

  • Screening rates
  • Stage at diagnosis
  • Incidence (new cases)
  • Prevalence (all existing cases)
  • Financial costs of cancer care or because of having cancer
  • Mortality (deaths from cancer)
  • Survival (how long people survive after diagnosis)
  • Morbidity (cancer-related health complications)
  • Survivorship (including quality of life after cancer treatment)

Cancer care continuum: The full scope and progression of cancer care, from promoting good health (wellness) to preventing cancer, detecting it early, diagnosing it, treating it, and surviving it.

Cancer control: Organized programs that focus on reducing the number of people who develop cancer, have complications from it, and die from it. It uses approaches that have been tested through research to control the number of cancer cases as well as the effects of cancer. Programs may include cancer prevention and early detection, treatment, palliative care, patient and family services, professional education and training, and cancer survivorship care. A cancer control program is successful when it assures that people are as healthy as possible, regardless of race, age, gender, location, social level, or economic status. See What Is Cancer Control?

Cancer deaths (see cancer mortality)

Cancer death rate (see cancer mortality rate)

Cancer disparities/Cancer health care disparities: Harmful, unfair differences in cancer prevention services, screening, detection, treatment, and follow-up care between population groups that affect how well people do after a diagnosis of cancer (their outcomes). These differences may be in the number of people receiving care, having nearby access to care, having sufficient health care insurance, and the quality of care available or received.

Cancer disparities result from economic, environmental, and social disadvantages. Populations most likely to experience cancer disparities are the same as those that experience health disparities

These differences between population groups can lead to certain groups bearing a disproportionate cancer burden. 

See Cancer Disparities ACS Research Highlights. See also health disparity.

Cancer epidemiology research: Studying the distribution and determinants of cancer—who gets it, where they live, and the risk factors that contribute to its development.

Cancer incidence (also called cancer occurrence): The number of new diagnoses of cancer, or new cases, in a group. Incidence counts can give information about a specific group but can’t be used to compare groups because the numbers alone don’t account for the size of the group or age ranges of the people in it. Comparing groups requires cancer incidence rates. Compare to prevalence.

Cancer incidence rate: The number of people who have a new diagnosis of cancer within a defined population (such as people aged 65 and older) and during a specified period of time (like 2019-2021). Incidence rates are usually given as the count per 100,000 population and are adjusted to account for differences in age.

Cancer mortality (also called cancer deaths): The number of people who die from cancer. Death counts can give information about a single group but can’t be used to compare groups because the counts don’t account for the size of the group or age ranges of the people in it. Comparing groups requires cancer death rates. See Understanding Cancer Death Rates.

Cancer mortality rate (also called cancer death rate): The number of people who die from cancer within a defined population such as Black women (but not limited to Black women with cancer) during a specific time period. The cancer death rate is not confined to people with cancer, it includes all people in the population. Cancer death rates are given as the number of deaths per 100,000 of the population. Researchers account (adjust) for age when they calculate death rates so they can track trends over time, and so they can compare groups. Cancer death rates are the best measures researchers use to track progress against cancer. See Understanding Cancer Death Rates.

Cancer occurrence (see cancer incidence)

Cancer-predisposition genes: Genes that are vulnerable to cancer-causing changes (mutations), which are sometimes inherited from a parent. Several dozen cancer-predisposition genes have been identified, and about 5% to 10% of all cancers result directly from those inherited. For example, BRCA1 and BRCA2 are inherited cancer predisposition genes, and mutations on them increase the risk of developing certain cancers, including breast, ovarian, and prostate.

Cancer prevalence: The number of people in a population with a history of a cancer diagnosis.

Cancer-related outcomes: The results of a cancer diagnosis—how it affects health, quality of life, and length of survival. These outcomes are influenced by: a patient’s overall health, access to quality health care, cancer type and stage, response to provided treatments, complications, and follow-up care.

Cancer relative 5-year survival rate: An estimate of the percentage of people who will be alive 5 years after a diagnosis of cancer compared with people who haven’t been diagnosed with cancer. The relative survival rate shows whether a disease shortens life and is used as a way to approximate the expected lifetime. For example, a relative 5-year cancer survival rate of 80% means that compared to the number of people without cancer who are alive, 80% of people with cancer will be living 5 years after their diagnosis.

Cancer surveillance research: Ongoing and systematic collection, analysis, interpretation, and reporting of cancer data about the new cancer cases, extent of disease, screening tests, treatment, survival, and death. Its goal is to use data to guide public health policy and action, such as the distribution of health care resources.

Cancer survival rate: The percentage of people who survive a certain type of cancer for a specific amount of time (often 5 years). For example, if a 5-year survival rate is 77%, it means that of all the people who have that type of cancer, 77 out of every 100 will be living at least 5 years after their diagnosis.

Cancer survivor: The American Cancer Society describes anyone who has been diagnosed with cancer as a cancer survivor, regardless of whether they are actively receiving treatment. 

Cancer treatment outcomes: How well a person is doing after being treated for cancer, which can depend on how well they respond to treatment, the treatment's side effects, their other health issues, and follow-up care, as well as on the facility where they received care and its geographic location.

Carcinogen: A substance known to cause cancer in living tissue, such as certain substances in cigarette smoke, alcohol, ultraviolet rays, processed meats (including bacon, ham, hot dogs, and lunch meat), radon, and asbestos. Most carcinogens start the process of carcinogenesis by interacting with a cell's DNA to produce mutations that damage the cell.

Carcinogenesis (also known as oncogenesis and tumorigenesis): The development of cancer. The process that changes healthy, normal cells to cancer cells. Carcinogenesis has three phases: initiation caused by cell damage, promotion led by uncontrolled replication of cells, and progression, which may involve the development of blood vessels around a tumor, migration of cancerous cells through the bloodstream or lymphatic system, and invasion of cancerous cells into normal tissue of nearby organs or those further from the tumor, causing new tumors (metastases) to develop.

Cell therapy: The prevention or treatment of certain diseases using specifically selected cells rather than chemical compounds like those used in chemotherapy and some targeted therapies. The cells can come from a donor or the patient, multiplied, genetically or pharmacologically altered in a lab, and returned to a patient, often by IV infusion. 

Bone marrow and stem cell transplants are the most frequently used cell therapy. They’re used to treat cancers in the blood. Another more recently discovered cell therapy is CAR (chimeric antigen receptor) T-cell therapy, which is being used to treat certain blood cancers. Scientists are studying how to use cell therapy in solid tumors. See Stem Cell or Bone Marrow Transplant and CAR T-cell Therapy and Its Side Effects.

Chromosome: Long thread-like strands of DNA in the nucleus of each cell. Each chromosome is made up of DNA tightly coiled many times around proteins (called histones) that support its structure. Each chromosome contains hundreds or thousands of individual genes. Most human cells have 23 pairs of chromosomes. In normal cells, one of each pair comes from the mother, and the other from the father. The exception is that males only have 1 copy of sex chromosomes. See also DNA, gene.

Cohort: A group of people, including groups of people who are in a study. See prospective cohort study.

Complete response: When tests after treatment show no signs of disease. A period when a disease is under control. A complete response may not be a cure.

Computational biology: This scientific, interdisciplinary field addresses theoretical and experimental questions in biology, behavior, and social systems by analyzing exceptionally large sets of data.

Computational biologists use data-analytical and -theoretical approaches, mathematical modeling (like algorithms), and computer simulations to understand and model the structures and processes of life.

Correlation/Correlational research: The process of establishing a relationship or connection between 2 or more measures.

Correlational research design investigates the relationship between 2 or more variables without interfering with or manipulating them. Results of a correlational study may find a positive or negative relationship, a linear or non-linear relationship, or a partial or multiple relationship. An example of a positive correlation is height and weight—taller people tend to be heavier, and vice versa. In some cases, positive correlation exists because one variable influences the other—such as ice cream sales and temperature. In other cases, the 2 variables are independent from one another and are influenced by a 3rd variable which may or may not be identified. Scientists can calculate the strength of a relationship between variables, but they cannot assume cause and effect.

CRISPR (stands for Clustered Regularly Interspaced Short Palindromic Repeats, also called CRISPR-Cas9, which stands for CRISPR-associated protein 9): One type of gene editing tool that gives scientists the ability to change DNA by adding, removing, or changing genetic material at particular spots in the genome. When the genome is edited, the characteristics of a cell or an organism may be changed.

CRISPR is faster, cheaper, easier to use, and more accurate than previous techniques of editing DNA. The method has profoundly changed biomedical research.

CRISPR-Cas9 is the most common, cheap, and efficient system used for genome editing.

Deep learning: Deep learning is a subset of machine learning. It's a family of machine-learning models based on layers of artificial neural networks, which can be a combination of hardware and software. Deep learning uses machine-learning techniques to solve real-world problems. It requires massive data sets to train machines to do what the brain does naturally. Deep-learning systems permit a machine to train itself and create new content—like images, text, or audio. In medicine, deep learning is used to classify skin cancer and identify diabetic retinopathy. See also machine learning.

Diagnostic biomarkers: A biomarker used to help identify and diagnose conditions. High glucose levels are a diagnostic biomarker for diabetes.

Diploid/Diploidy: Ploidy refers to the number of chromosome pairs in a cell. Normal cells have 23 pairs, known as diploidy. See also ploidy and aneuploidy.

DNA (deoxyribonucleic acid): The hereditary material, sometimes referred to as the genetic blueprint, in humans and almost all other organisms. DNA holds genetic information on cell growth, division, and function and is passed from one generation to the next. Nearly every cell in a person’s body has the same DNA.

Most DNA is located in the cell nucleus, but a small amount of DNA can also be found in the cell’s mitochondria. When cells divide, each new cell needs to have an exact copy of the DNA that was in the old cell.

DNA chains coil into 46 chromosomes, 23 from each parent. See also RNA.

Discovery research: Experiments with genes, cells, animals, or people to find a new or improved understanding of an action, health behavior, process, technique, technology, or model to improve care.

Disparity (See cancer disparity and health disparity)

Epidemiology: The study of the occurrence, distribution, and possible causes of diseases (like cancer) in a group of people.  

Epigenetic age/epigenetic aging (see biologic age)

Epigenetic changes (see epigenetics)

Epigenetic mark (see epigenetics)

Epigenetic signature (see epigenetics)

Epigenetics/epigenetic changes (also known as epigenetic marks or signatures): The study or process of how a person’s behaviors (like diet and exercise) and environment (like toxins, healthy or unhealthy stress management, and draining or inspiring school/work environments) can cause changes that add or remove special marks on a gene’s DNA that affect the way your genes work and how active they are. 

Epigenetic changes affect how your body reads a DNA sequence but doesn’t change the sequence as genetic changes do. Specifically, epigenetic changes, turn genes “on” and “off.” Different genes are more active in some cells than in others. Even within a certain cell, some genes are active at some times and inactive at others. Epigenetics has a strong influence on how a person develops and can alter individual traits.

Behaviors that may change epigenetic patterns/marks:

  • Alcohol consumption
  • Environmental pollutants
  • Nutrition/diet
  • Obesity
  • Physical activity
  • Psychological Stress
  • Smoking
  • Working habits (like working night shifts)

Some epigenetic changes increase your risk of developing cancer and other health conditions. It may be easier for scientists to find and remove bad epigenetic marks, though, compared to fixing a hardcopy genetic mutation. For example, reversing epigenetic changes may reveal a potential target for new treatments. 

Other helpful things to know about epigenetics: 

  • Epigenetic modifications are heritable and can be passed between generations.
  • Epigenetic changes may be reversible (unlike genetic changes). 
  • Your epigenetics change throughout your life. 
  • Epigenetics explains how early experiences can have lifelong impacts.
  • Young brains are particularly sensitive to epigenetic changes.
  • Epigenetics explains how people with identical DNA can have dramatically different looks and behaviors (phenotypic differences).

Epigenome: A collection of chemical marks that accumulate on a gene’s DNA as the body develops (also known as epigenetic marks or epigenetic signatures). Known as the epigenome, this collection of marks “tells” the gene what to do, where to do it, and when to do it.

Etiology: The study of the causes of a disease. There are many possible causes of cancer. Research is showing that both genetics (genes passed on from your parents) and lifestyle (including exposures to carcinogens) are major factors involved in the development of many cancers. See also carcinogen, gene.

Experimental study: When researchers introduce an intervention and study the effects. Randomized controlled trials are a type of experimental study. Unlike correlational research where a scientist looks for associations among naturally occurring variables, in experimental studies, the researcher may introduce a change and then monitor its effects. 

Federal Poverty Line (FPL): The income level that’s used to set eligibility limits for several programs and benefits in the United States. It’s published each year by the US Department of Health and Human Services. These programs include Medicaid, Children’s Health Insurance Program (CHIP), Supplemental Nutrition Assistance Program (SNAP), Supplemental Nutrition Program for Women, Infants, and Children (WIC), and other “welfare” programs.

FPL (see Federal poverty line) 

Functional precision medicine: pre-clinical research platform where scientists use live tumor cells taken from patients to identify new drugs, including the identification of biomarkers to personalize the use of these drugs.

A piece of DNA. Genes have information on inherited traits such as hair color, eye color, and height, as well as susceptibility to certain diseases. Every person has more than 20,000 genes.

Most genes are the same in all people and they vary in size based on how many DNA bases they include. Less than 1% of genes are slightly different between people.

Some genes carry instructions to make proteins, which are required for the structure, function, and regulation of the body’s tissues and organs.

All the genes in a cell aren’t needed all the time. So the body has ways to turn them “on” (gene expression) and turn them “off.” For instance, actions such as coiling and uncoiling the DNA can turn a gene on or off based on how close it is to other genes. The mechanisms that turn the genes on and off can be influenced by lifestyle, environment, and age.

Gene editing (see CRISPR)

Gene expression: The process of the body turning encoded information in a gene into a function. For instance, a gene may have the code for making a certain protein. When the gene is “expressed,” a protein is made. Proteins dictate a cell’s function. 

The term gene expression communicates how many, how often, and when proteins are created from the instructions within the genes. Some researchers describe gene expression as volume control. Epigenetic changes affect gene expression to turn genes “on” and “off” (compared genetic changes can alter which protein is made, but not how much or when). 

Genetic changes (see genetic mutation)

Genetic mutations (also known as genetic variants and genetic changes): Permanent changes in the DNA sequence of a gene are called gene mutations. Some scientists think that “gene variant” is a more accurate term because changes in DNA do not always lead to disease. Sometimes the terms are used as synonyms.

Genetic predisposition or genetic susceptibility: People who inherit certain changed genes that make them more likely (more disposed or more susceptible) to develop cancer are said to have a genetic predisposition to a cancer or certain types of cancer. Sometimes this is referred to as having a family cancer syndrome. But having a genetic predisposition doesn’t mean that person will develop cancer. And if they do develop cancer, it may not be caused by the inherited genetic mutation.

Genetic susceptibility (see genetic predisposition)

Genetic variants (see genetic mutations)

Genome: A complete set of DNA. Almost all of our cells contain two copies of a person’s genome.

Genome editing (see CRISPR)

Genomics: (see human genomics)

Germline pathogenic variations: A type of mutated gene that gets passed down from a parent to child and that causes disease, such as cancer. The BRCA1 and BRCA2 mutations are examples because they are passed down by parents and increase the risk of developing several types of cancer.

Germline variations: The type of mutated gene that are passed from a parent to a child. Germline variations that cause disease are germline pathogenic variations.

Global cancer burden: An assessment of the number of cancer cases and the effects of cancer across the world. The global cancer burden may be lowered by improving cancer prevention programs, broadening cancer screening programs, expanding high-quality treatment and patient support, and prioritizing public health awareness and education campaigns in every country. See ACS Global Cancer Control Work.

Gut microbiome: A collection of microorganisms like bacteria, viruses, and fungi that mostly live in the digestive tract. Every person's gut microbiome is uniquely shaped by their diet, lifestyle, genetics, and environment. Gut bacteria help with day-to-day functions like synthesizing vitamins, digesting food, and metabolizing drugs. They also help regulate the immune system and protect the body from potentially harmful bacteria. Recent findings have shown that the gut microbiome can help cancer grow and also help keep it from growing.

Health care barriers: Factors that prevent a person from getting to (accessing) quality health care and services, which may include lack of adequate health insurance, location of health centers, available transportation, and time off from work.

Health disparity: Health disparities are usually noticeable and significant differences between population groups in regard to their health, health care, or both, in ways that are not fair or equal. Health disparities contribute to health inequalities. Differences can be in the number of people receiving care, access to nearby care, sufficient health insurance, quality of care, and more.

Such differences are preventable, as they're closely linked with economic, political, social, and/or environmental disadvantages. Health disparities may occur because of:

  • Age
  • Discrimination or exclusion, or both
  • Disability
  • Education
  • Gender (or gender identity)
  • Geographic location
  • Income
  • Literacy
  • Mental health
  • National origin
  • Race or ethnicity
  • Religion
  • Sexual orientation or gender identity
  • Socioeconomic status

Cancer disparities are one type of health disparity.

Health equality: Providing everyone with the same tools and resources for health care. Compare with health equity.

Health equity: The state in which everyone is able to reach their full health potential, and no one is at a disadvantage for attaining this potential on the basis of race/ethnicity, gender, health insurance coverage, disability, place of residence, or other social circumstances, such as lack of access to good jobs with fair pay, quality education and housing, safe environments, and health care.

Equity is the fair treatment, access, opportunity, and advancement for everyone while addressing needs and eliminating barriers that prevent the full participation and success of all people.

Achieving health equity requires removing obstacles to health such as poverty and discrimination, as well as their consequences, including powerlessness and lack of access to good jobs with fair pay, quality education and housing, safe environments, and health care.

Health equity is not the same as health equality. Equity acknowledges that people have different circumstances or barriers they need to overcome, often through no fault of their own. These barriers are often because of deeply rooted, longstanding inequities at all levels of society that will take an intentional effort to address in order to have equal cancer outcomes. Because of this, the tools and resources needed for health care need to be different from one person to the next.

High-thoughput sequencing (see next-generation sequencing)

Hispanic: A broad term that refers to people descended from Spanish-speaking countries or with Latin American (South America, Mexico, Central America, and certain Caribbean islands, including Cuba, Jamaica, and others.) ancestry. The term Hispanic is more commonly used in the Eastern US and is generally preferred by those of Caribbean and South American ancestry or origin. Hispanic is considered an ethnicity, as Hispanic people can be of any race. See also Latino.

Human genomics: The study of a person’s genome—a complete set of DNA, including all of its genes.

Incidence (See cancer incidence)

Interleukins: Proteins required for controlling acute inflammatory responses in the body. Interleukins are the body’s defense against “invaders,” like wounds, viruses, or diseases. 

Interleukin-6 (IL-6): A protein produced by various cells in the body to help regulate immune responses. The production of c-reactive protein (CRP) is thought to be linked with the production of IL-6. Testing the levels of interleukin-6 is a potentially useful mark of how well the immune system is functioning. Too much IL-6 has been linked with diabetes, rheumatoid arthritis, and cancer. Both physical and psychological stress can cause temporary increases in IL-6.

Internet of Everything (IoE): A 21st century digital system is an intelligent network of people, process, data, and things (objects, devices, appliances, and so forth that use implanted sensors to communicate across the network). This interconnectedness allows data from all devices to be analyzed and processed together. IoE works in sync with technologies such as artificial intelligence, machine learning, and the cloud. These processes ensure the correct information is relayed to the right destination across the network and to leverage data faster.

Internet of Things (IoT): A subset of the Internet of Everything, which includes those devices with sensors or other technology that are connected by a network and that can exchange data over the internet without human intervention. Examples of IoT devices include pacemakers, smart thermostats, home security systems, and self-driving cars.

Intervention: A program or set of activities designed to help people or populations change a particular behavior (like sitting too much or forgetting to put on sunscreen) that increases their risk for a particular disease.

In vitro: A Latin term that means grown and studied in a dish, or in the lab, compared to being grown in a living being—in vivo.

In vivo: A Latin term that means grown and studied in a living being, such as a lab mouse or human

Latino: A broad term that refers to people in the US with Latin American ancestry. Unlike Hispanic, Latino includes people from Brazil, who speak Portuguese. Latino has replaced the terms Chicano and Mexican American and is used primarily west of the Mississippi River. Like the word Hispanic, the word Latino identifies an ethnicity, as Latino people can be of any race. Latino is used for males, Latina for females, and Latinx to be gender neutral. See also Hispanic.

Longitudinal study: A research design that involves repeated observations or measurements of the same variables—such as weight, existence of a disease, like cancer, and foods eaten (diet)—over a short or long period of time—sometimes lasting decades. Researchers don't interfere with the participants' day-to-day activities but only collect qualitative and quantitative responses through surveys, interviews, or other tools. Longitudinal studies are a method of correlational research, meaning it helps scientists discover the relationship between variables in a specific population.

Machine learning: Machine learning is a subfield of artificial intelligence. It’s a technology that uses current and historical data along with algorithms and statistics formulas to train computers to recognize patterns to perform tasks without having a specific set of instructions (like software or code) to follow. It can analyze and make decisions about large amounts of complex data exponentially faster than people can, and it can improve with experience. Machine learning is used for such things as fraud detection and recommending products based on previously bought items. See also deep learning.

Medicaid expansion: The part of the Affordable Care Act that called for increasing the number of low-income people in the United States who qualify for the health insurance coverage provided by Medicaid, a government program run by each state.

Metabolites: Small molecules that are made and stored when the body breaks down food, drugs, or its own tissue and that are affected by the environment and diseases like cancer.

Metabolomics: The study of small molecules, called metabolites, that are made and stored when the body breaks down food, drugs, or its own tissue and that are affected by the environment and diseases like cancer.

Microenvironment (see tumor microenvironment)

Mitochondria: Structures in normal and tumor cells that generate most of the energy needed to power the cells’ (or tumors’) biochemical reactions required to function and grow. Mitochondria act like a digestive system that takes in nutrients, breaks them down, and creates energy for the cell.

Molecular marker (see biomarker):

Monitoring biomarkers: Biomarkers that help recognize the status of disease or side effects of treatment. Tumor DNA (ctDNA) is a monitoring biomarker for certain metastatic cancers.

Mutation (see genetic mutation)

Native Hawaiian and Other Pacific Islander (NHPI): A broad term that refers to a person having origins in Hawaii (Hawaiʻi), Guam (Guåhan), Samoa (Sāmoa), Fiji or other Pacific Islands throughout Polynesia, Micronesia, and Melanesia.

Natural killer cells (NK cells): These immune cells typically patrol the bloodstream, seeking out cells infected with viruses and tumor cells that they destroy in their early stages before viruses or cancer cells spread. They’re called “natural” killers because they can recognize potentially harmful cells and kill them without ever having seen them before.

NK cells work by scanning cells for markers that indicate whether the cells are healthy or diseased. When they detect harmful cells, NK cells release deadly chemicals and kill them.

NK cells are highly efficient at killing tumor cells within the circulating blood and can help block metastasis, but they are less efficient at killing tumor cells in the microenvironment.

Another class of NK cells communicate rather than kill. They release cytokines, which “alert” other immune cells to attack harmful cells. 

Next-generation sequencing (also known as NGS and High-throughput sequencing): Technology that allows for simultaneous sequencing of DNA and RNA in multiple people at the same time. Compared to traditional sequencing, which determines the sequence one section at a time, next-generation sequencing in much faster, less expensive, and delivers a much larger magnitude of information. Making sense of these huge datasets requires bioinformatics and computational biology. NGS has revolutionized the field of personalized medicine (precision medicine).

NGS (see next-generation sequencing)

Observational study: When researchers observe the effect of a risk factor, diagnostic test, treatment, or other intervention without trying to change who is or isn't exposed to it.

Oncogenes: A group of genetic mutations that have the potential to cause cancer and that give cancer cells an advantage to grow and survive.

Oncogene addiction: The dependency of certain tumor cells on a specific, individual oncogene to grow and survive.

Oncogenesis (See carcinogenesis)

Oncogenic fusion gene: A hybrid gene formed from 2 or more previously independent genes that plays a leading role in the development and progression of cancer. These hybrid, fused genes are read (transcribed) and translated as a single unit, which may lead to the production of defective proteins that cause cancer to grow and spread.

The prevalence of fusion genes varies widely across different cancers, and many fusion genes are specific to certain cancer sub-types. Rapidly and accurately identifying fusion genes can be an important part of diagnosis because specific gene fusions characterize cancer subtypes. A stratified diagnosis can predict a patient's prognosis, response to treatment, and survival.

Fusion genes are potentially excellent sites for new treatments to target. Several drugs have been successfully developed to inhibit fusion genes.

Pathogenic mutations (see pathogenic variants)

Pathogenic variants (PVs, also known as pathogenic mutations): Genetic variants or mutations that lead to disease.

Pharmacokinetics: The study of how the body interacts with medicines from the time a person takes a drug throughout its journey in the body. 

Ploidy: The number of sets of chromosomes contained in a cell, whether it’s a normal cell or cancer cell. See also aneuploid, diploid.

Precision medicine (also called personalized medicine): A clinical approach for medical prevention and treatment that's tailored based on a person's lifestyle, environment, and the specific genes, proteins, and other substances in their body. Precision medicine is the opposite of the one-size-fits-all approach to prevention and treatment, where an average strategy applied to everyone. A personalized approach  helps doctors and researchers more accurately predict which prevention and treatment methods will work for a specific disease in a particular person.

The 2 types of treatment most often used in precision medicine are:

  • Targeted therapy, which uses medicines designed to attack a specific target on cancer cells
  • Immunotherapy, which uses medicines that help the body’s immune system attack the cancer

Preclinical studies: Research that takes place before any testing in humans is done—before clinical trials. Preclinical studies may study if a drug, procedure, or treatment is likely to be useful. In the commonly used description about the research continuum, “bench to bedside,” preclinical studies are the bench—meaning they occur in a lab setting. Preclinical studies may be conducted in a test tube or cell culture (in vitro) or in animals, such as mice (in vivo).

Predictive biomarkers: Biomarkers that signal the likelihood a person has to develop a reaction after exposure to a disease, treatment, or substance in the environment. For instance, presence of the hormone ER (ER+) in a breast tumor is a predictive biomarker that tamoxifen may be an effective treatment.

Predisposition genes (see cancer-predisposition genes and genetic predisposition)

Prevalence (see cancer prevalence)

Prognostic biomarkers: Biomarkers that indicate the chances of a disease progressing or recurring. For instance, the protein HER2 is a prognostic biomarker for breast cancer.

Promoter (also known as DNA promotor): A region of DNA where transcription (copying the information in DNA to mRNA) of a gene is initiated. Promotor regions describe the direction of transcription and point out which DNA strand will be transcribed.

Promoters work with DNA regions known as enhancers to ensure a good copy of that gene. DNA bends to put the enhancer section close to the promotor section. Mutations can occur in the coding (enhancer region) or in the promotor region. Many studies suggest that DNA promotors may be the main cause of many human diseases, especially diabetes.

Prospective Cohort Study: A long, on-going (longitudinal) research study that captures and compares years of data from a group of people (cohort) to learn how specific characteristics or risk factors affect the rate of developing diseases such as cancer.  Prospective means data is collected before anyone has developed cancer. Cohort studies are a type of observational study.

Research continuum: The full scope of research—often referred to as bench to bedside. Research may start in a research lab (pre-clinical research or research at the bench), occur as part of clinical trials, be done by health care providers or within health care systems (at the bedside), and be conducted within communities.

Response biomarkers: Biomarkers that help confirm whether a prevention method or treatment worked. For instance, after vaccination, antibodies are the response biomarkers.

Ribonucleic acid: See RNA.

RNA (ribonucleic acid): RNA is found in all living cells of the body. Its most notable role is to act as a messenger (mRNA) by contains instructions from DNA that are translated by the cell to make proteins. When RNA does not carry a code for a protein, it’s called non-coding RNA (ncRNA). There are many additional types of RNA with various functions within the cell.

RNA, like DNA, is made of nucleotides (chains of nucleic acids). See also DNA.

RNAseq: See RNA sequencing.

RNA sequencing (RNAseq): A technique used to learn the exact order of the nucleotides that make up RNA molecules in healthy or diseased tissue or cell. It provides a picture of how the blueprint (DNA) is being read.

RNAseq is a powerful tool for understanding cancer at the molecular level (how individual cells employ their mRNA and proteins) and for developing new strategies to prevent or treat cancer. For instance, RNAseq allows scientists to compare how genetic instructions change before and after drug treatment.

RNAseq can reveal gene fusions, splicing variants, mutations, and differences in gene expression between cell samples.

Scientists can use RNA sequencing for analysis of:

  • Cell collections
  • Tissue sections, called bulk RNA sequencing
  • Liquid biopsies (See Biopsy Types and Liquid Biopsy: Past, Present, Future.)
  • Single cells, called single-cell RNA sequencing or scRNA-seq, which can distinguish single-cell RNA biology up to 20,000 individual cells simultaneously, and show how cells change over time.

Single nucleus RNA (snRNA seq): A technique to isolate RNA from the nucleus of a cell.

Single-cell resolution/Single-cell analysis (scRNA-seq, also known as single-cell imaging): The use of new methods and technologies that show more details than a microscope, allowing researchers to see a different view of single cells in tissue. This technique reveals the specific population of cells in a selected area of tissue. With these tools, scientists can analyze each cell individually and learn how the position of each cell has a role in the tissue’s architecture. This detailed information is critical to better understanding the biological function of both normal and diseased tissues.

Spatial RNA sequencing, spRNAseq, also called spatial transcriptomics): This method allows scientists to view a specific region within a cell, then sequence all RNA transcripts (copy of DNA instructions) found in that region. Using this, scientists can map the variation of gene expression (which proteins are made by the cells) across the region of interest.

Organisms function based on the spatial organization and spatial of cells. If spatial orientation is disrupted, there could be a loss of biological function.

A better understanding of spatial information will help scientists better understand how tumor cells communicate with each other, escape tracking by the immune system, become resistant to drugs, and metastasize.

For spatial sequencing, scientists use immunofluorescence microscopy and next-generation sequencing to determine the transcripts in the region. 

Safety biomarkers: Biomarkers that help identify possible toxic responses to treatment or harmful environmental exposures. For instance, creatinine is a safety biomarker for drugs that can potentially affect the kidney.

Screening prevalence: The number of people in a population who receive cancer screening.

Sedentary: Sitting, reclining, or lying down while awake and expending very little energy. 

Signature marker (see biomarker)

Social determinants of health: Social determinants of health are non-medical factors that influence health, the ability to function, risk for health problems, and quality of life. These include conditions in the environments where people are born, live, work, play, learn, worship, and age, as well as the social, economic, and political systems that shape those conditions of daily life. 

The occurrence of cancer can be positively or negatively affected by social determinants of health based on how they affect educational and job opportunities, income, housing, transportation, public safety, food security, social inclusion and non-discrimination, and access to affordable health services of high quality. 

Social determinants of health are closely linked with health disparities.

Stroma: The cells and tissues that support and give structure to organs, glands, or other tissues in the body. It’s made mostly of connective tissue (made mostly of fibroblasts), blood vessels (lined by endothelial cells), lymphatic vessels, immune cells, and nerves.

The stroma provides nutrients to other tissues and organs, removes waste and extra fluid, and may be involved in the body's immune response, modulating inflammation levels. When stromal cells secrete growth factors, they promote tumor growth, invasion, and metastasis.

Structural racism/Systemic racism: Normalized historical, cultural, political, and institutional practices that govern society and benefit White people and disadvantage people of color. These can include housing policies, educational systems, and employment practices that reinforce and perpetuate inequities among racial groups.

Survival rate: The percentage of people who are alive at a certain time after diagnosis of a life-threatening disease, like cancer. The survival rate doesn’t determine how long a person will live after a diagnosis of cancer, but it may help people better understand how likely it is that treatment will be successful.

For cancer, it’s common to see a 5-year period after diagnosis as the marker, referred to as a 5-year survival rate. 

Survivorship: The time in a person's life from the diagnosis of cancer until death. The study of survivorship evaluates a person's quality of life, physically, mentally, and spiritually.

Susceptibility biomarker: A biomarker that signals the potential, or risk, a person has to develop a disease before they have symptoms. For instance, low-density lipoprotein (LDL) cholesterol is a susceptibility biomarker for heart disease.

Targeted therapy: A type of cancer treatment that uses drugs or other substances designed to “target” a specific aspect of cancer cells, like a mutated gene, and kill them without harming normal cells. Targets may also be in the tumor’s microenvironment, such as a protein that sends messages to tell the cancer cell to grow and copy itself.

Different targeted therapies work differently. For example, a targeted therapy can block or turn off signals that make cancer cells grow, or it can signal the cancer cells to destroy themselves.

Targeted therapy is an important type of cancer treatment, and researchers will develop more targeted drugs as they learn more about specific changes in cancer cells. 

tbNGS (see next-generation sequencing)

TNBC (see triple-negative breast cancer)

Triple-negative breast cancer (TNBC): A subtype of breast cancer that grows faster and is more likely to spread and recur. It is more common in women younger than age 40, who are Black, or who have a BRCA1 genetic mutation. 

It’s called triple negative because the cancer cells in TNBC don’t have receptors for the hormones estrogen (ER) or progesterone (PR). Plus, TNBC cells make very little or none of the protein called HER2 (human epidermal growth factor). That means all 3 biopsy tests to check for these hormones and the HER2 protein come back "negative." 

Tumor-based next-generation-sequencing (see next-generation sequencing)

Tumor microenvironment: If a tumor is a castle, the tumor’s microenvironment is everything immediately around the castle—like the moat, high walls, courtyard, and soldiers—that affects how easy it is to get to the castle. The immediate area surrounding a tumor includes blood vessels that provide nutrients to the tumor, immune cells that may protect the tumor, structural matter called the extracellular matrix, and other cells that support the tumor (like stromal cells) or that make space for it to get larger.

A tumor and its microenvironment constantly interact, which influences if and how the tumor grows. Cells in the microenvironment can perform both pro- and anti-tumor functions, controlling how the cancer progresses and spreads.

This relationship between the microenvironment and tumor means successful cancer treatments often need to target more than just the cancer cells. They may need to target cells in the microenvironment to cut off the tumor’s nutrients or weaken its protection. 

Tumorigenesis (see carcinogenesis)

Underrepresented minorities (URM) in health-related science: Racial and ethnic groups that are particularly underrepresented across many career stages: African American/Black, Hispanic/Latino, American Indian and Alaska Native, Native Hawaiian and other Pacific Islander groups. The ACS Diversity in Cancer Research (DICR) program focus on racial and ethnic underrepresented minorities.

Wnt gene (see Wnt signaling pathway)

Wnt protein (see Wnt signaling pathway)

Wnt signaling pathway: A complex and diverse communication channel in cells that has many signaling branches. Wnt genes code for a large family of Wnt proteins that “carry messages” across the Wnt pathway. These messages regulate many critical cell functions, including the beginning and end of cells.

In the tumor microenvironment, Wnt signaling can turn immune cells “on and off,” regulating the cell’s anticancer immune response, meaning the signals can help tumors grow or stop them from growing.

Defective, or disrupted, Wnt signaling is part of the cause of cancers in the breast (including triple-negative breast cancer), cervix, colon, lung, and skin, as well as some blood cancers. Multiple players along the pathway have been identified as targets for anticancer drugs to disrupt signals that let cancer cells grow.