later turn into cancer. These changes can be detected by
the Papanicolaou (Pap) test and treated to prevent the
development of cancer.
Chemotherapy The use of different drugs to kill or slow the
growth of cancer cells.
Chromosome Structure within the nucleus of a cell that
contains genetic information (DNA) and its associated
proteins (see Deoxyribonucleic acid and Epigenetics).
Except for sperm and eggs, nearly all nondiseased human
cells contain 46 chromosomes.
Chronic lymphocytic leukemia (CLL) The most common
type of leukemia (blood cancer) diagnosed among adults
in the United States. CLL arises in lymphocytes, most
commonly B lymphocytes, in the bone marrow, which then
enter the blood. It is usually slow-growing, but in some
people it can be fast-growing.
Chronic myelogenous leukemia (CML) A slowly progressing
type of leukemia (blood cancer) in which too many white
blood cells (not lymphocytes) are made in the bone marrow.
Also called chronic granulocytic leukemia and chronic
Clinical trial A type of research study that tests how well
new medical approaches work in people. These studies test
new methods for screening, preventing, diagnosing, or
treating a disease. Also called clinical study.
Colonoscopy Examination of the inside of the colon using a
colonoscope that is inserted into the rectum. A colonoscope
is a thin, tube-like instrument with a light and a lens for
viewing. It may also have a tool to remove tissue to be
checked under a microscope for signs of disease.
Colorectal cancer A group of cancers that start in the colon
or the rectum. More than 95 percent of colorectal cancers
are adenocarcinomas that arise in cells forming glands that
make mucus to lubricate the inside of the colon and rectum.
Before a colorectal cancer develops, a growth of tissue or
tumor usually begins as a noncancerous polyp on the inner
lining of the colon or rectum. Most polyps can be found—
for example, through colonoscopy—and removed before
they turn into cancer.
Computational biology The development of data-analytical
and theoretical methods, mathematical modeling, and
computational simulation techniques and their application
to the study of biological, behavioral, and social systems.
Computed tomography (CT) A series of detailed pictures
of areas inside the body taken from different angles. The
pictures are created by a computer linked to an X-ray
machine. Also called CAT scan, computerized axial
tomography scan, and computerized tomography.
Cyclin-dependent kinases (CDK) A family of proteins that
have important roles in controlling a number of cell processes,
including cell multiplication. To function effectively, CDKs
must attach to a small protein called a cyclin.
Death rate/mortality rate The number of deaths in a certain
group of people in a certain period of time. Death rates may
be reported for people who have a certain disease; who live
in one area of the country; or who are of a certain gender,
age, or ethnic group.
Deoxyribonucleic acid (DNA) The molecules inside cells that
carry genetic information and pass it from one generation
to the next.
Drug resistance The failure of cancer cells, viruses, or
bacteria to respond to a drug used to kill or weaken them.
The cells, viruses, or bacteria may be resistant to the drug
at the beginning of treatment or may become resistant after
being exposed to the drug.
Electronic cigarette (e-cigarette) A battery-powered device
that delivers nicotine by vaporizing a nicotine solution,
rather than by combusting tobacco as do traditional
cigarettes and cigars.
Endpoint In clinical trials, an event or outcome that can be
measured objectively to determine whether the intervention
being studied is beneficial. The endpoints of a clinical trial
are usually included in the study objectives. Some examples
of endpoints are survival, improvements in quality of life,
relief of symptoms, and disappearance of the tumor.
Epigenetics The study of heritable changes in gene
expression or cellular phenotype caused by mechanisms
other than changes in DNA sequence. Examples of such
changes might be DNA methylation or histone deacetylation,
both of which serve to suppress gene expression without
altering the sequence of the silenced genes.
Erdheim-Chester disease A rare multisystem disorder
characterized by histiocytosis, a condition in which
the immune system produces excess numbers of white
blood cells called histiocytes. The histiocytosis leads
to inflammation that can damage organs and tissues
throughout the body; this tissue damage can lead to
organ failure. Bone pain is the most frequent symptom of
Epigenetic mark A chemical mark on DNA (see
Deoxyribonucleic acid) and histones (see Histone) that
can control the accessibility of genes. The collection of
epigenetic marks across the entire genome is referred to as
Familial adenomatous polyposis (FAP) An inherited
condition in which numerous polyps (see Polyp) can
develop in the colon and rectum. It increases the risk of
colorectal cancer. Also called familial polyposis.
Five-year survival rate The percentage of people in a specific
group, for example, people diagnosed with a certain type
of cancer or people who started a certain treatment, who
are alive five years after they were diagnosed with or started
treatment for a disease, such as cancer. The disease may or
may not have come back.
Gastric cancer Cancer that arises in cells lining the stomach.
Cancers starting in different sections of the stomach
may cause different symptoms and often have different
outcomes. Infection with the bacterium Helicobacter pylori
(see Helicobacter pylori) is a major cause of gastric cancer,