Most cancers arise and progress as a result of the
accumulation of genetic mutations that disrupt the orderly
processes controlling the multiplication and life span of
normal cells. There are numerous factors that cause cells
to acquire genetic mutations (see sidebar on Sources of
Genetic Mutations, p. 19 and Figure 4, p. 26). The identity,
order, and speed at which a cell acquires genetic mutations
determine whether a given cancer will develop and, if a
cancer does develop, the length of time it takes to happen.
Knowledge of the causes, timing, sequence, and
frequency of the genetic, molecular, and cellular changes
that drive cancer initiation and development provides
opportunities to develop screening strategies to detect, if
present, precancerous lesions or cancer at an early stage of
development (see Figure 7, p. 39). If precancerous lesions
are found to be present they can be removed before they
become cancer, something that is sometimes referred to
as cancer interception. Finding cancer early, before it has
spread to other parts of the body, makes it more likely that a
cancer can be intercepted and a patient treated successfully.
WHAT IS CANCER
HOW IS IT DONE?
Cancer screening refers to checking for precancerous
lesions or cancer in people who have no signs or symptoms
of the cancer for which they are being checked. It has many
benefits, but it can also result in unintended adverse
consequences (see sidebar on Cancer Screening, p. 40).
Thus, population-level use of a cancer screening test must
decrease deaths from the screened cancer and provide
benefits that outweigh the potential risks. Determining
whether broad implementation of a screening test across the
population can achieve these two goals requires extensive
research and careful analysis of the data generated.
There are five types of cancer for which screening tests
have been developed and used in the clinic to screen
generally healthy individuals (see sidebar on Cancers for
Which Population-level Screening Has Been or Is Being
Performed, p. 42). Some of these tests can be used to prevent
cancer from developing because they detect precancerous
changes in a tissue that can be removed before they have a
chance to develop into cancer. Others can detect cancer at
an early stage of development, when it is more likely that
a patient can be treated successfully.
For cancers other than breast, cervical, colorectal, lung, and
prostate cancer there has never been population-level use
of a screening test for individuals at average risk for disease.
Thus, more research is needed to identify biomarkers and
• Research identifying the biological
underpinnings of cancer initiation and
development has led to screening tests
that can be used for cancer prevention
and early detection.
• There are five types of cancer for which
screening tests have been developed
and used in the clinic to screen
generally healthy individuals.
• Independent groups of experts rigorously
evaluate data on the benefits and
potential risks of cancer screening tests
before putting forth recommendations
about the use of the tests.
• Every person has a unique risk for each
type of cancer based on his or her genetic,
molecular, cellular, and tissue makeup,
as well as his or her lifetime exposures
to cancer risk factors.
• Some people are at increased risks for
certain cancer types and may need to
take measures to reduce the risks.
• There are significant disparities in cancer
screening rates among certain segments
of the U.S. population.
In this section you will learn: