The primary cause of cancer initiation and development
is 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 genetic mutation acquisition (see Figure 3, p. 24),
and 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 us with opportunities
to develop screening strategies that allow us to detect, if
present, precancerous lesions or cancer at an early stage of
development (see Figure 8, p. 39). Precancerous lesions can
be removed before they develop into 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
the patient treated successfully.
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 Screening Tests Exist, p. 40). 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. Recommendations on how best to
use these tests are discussed in the information to follow.
One area of intensive research investigation aims to gain
a deeper understanding of the biology of precancerous
lesions ( 93, 94). The goal is that as we learn more about
the genetic, molecular, and cellular characteristics of
precancerous lesions, we can develop new screening
tests and cancer prevention therapeutics, as well as more
precisely identify those for whom cancer screening and
cancer prevention therapeutics would be beneficial.
WHO SHOULD BE SCREENED?
Screening to detect cancer before an individual shows
signs or symptoms of the disease for which he or she is
being screened has many benefits, but it can also result in
unintended adverse consequences (see sidebar on Cancer
Screening, p. 41). Thus, population-level use of a cancer
screening test must not only decrease deaths from the
screened cancer, but it must also 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.
• Understanding of the biology 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 test;
these recommendations are updated periodically to incorporate new evidence.
• Areas of disagreement among different recommendations highlight areas
in which more research is needed.
• Some people are at increased risks for certain types of cancer and may need
to take measures to reduce the risks.
In this section you will learn: