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M
edical advances in recent decades
have led to targeted treatments
for some cancers. This has raised
hopes for similar breakthroughs in
the fights against other diseases.
Politicians are getting involved, calling for further work
in “precision medicine” and individualized approaches
to patients. Medicine in the 20th century identified
specific causes and treatments for many diseases, but
treatment outcomes remain highly variable. We have
learned that most diseases and injuries are caused
by multiple factors, meaning that a specific event,
condition or individual characteristic by itself is not
generally sufficient to produce the disease. When
our knowledge of any of the integral factors of a
given disease is incomplete, we remain puzzled by
varying outcomes, and our preventive and treatment
interventions lack desirable precision and efficacy.
Sometimes unbeknownst to us there are several
different sets of causal mechanisms that can lead to
a specific disease. Other times individuals’ responses
to a known set of causal factors remain variable for
unknown reasons. Advances in genomic studies open new
possibilities for identifying causes of variability — both in
responses to harmful factors and in the efficacy of specific
treatments. This has advanced modern oncology, and a
similar approach could benefit other areas of medicine,
too. First we will examine how genetic testing enables
precision medicine in two common cancers, breast cancer
and lung cancer, then we will discuss how precision
medicine pertains to dive medicine.
Breast cancer provides a good example of how genetic
testing contributes to precision medicine. In the general
population, breast cancer is caused by multiple factors.
About 5 to 10 percent of breast cancer is caused by
inherited genetic mutations. The two most important
mutations related to breast cancer, BRCA1 and BRCA2,
are present in 0.1-0.2 percent of the general population
and in a much higher percentage in some minorities.
The overall risk to women in the general population of
developing cancer by age 70 is 12 percent. However, the
average risk is much higher for carriers of BRCA1 (55-65
percent) and BRCA2 (45 percent).
While not all women with hereditary risk factors
develop breast cancer, the risk for some women may be
greater due to other known or unknown factors. Breast
cancer is less common in men (0.1 percent), but in men
who have the BRCA2 mutation the risk of breast cancer
is about 7 percent — 70 times that of noncarriers. In
addition to genetic testing of the individual, which
provides information about the risk of acquiring the
breast cancer, genetic testing of the cancer helps
medical professionals establish a prognosis, choose
effective therapies and avoid therapies to which the
cancer is resistant.
In lung cancer today, genetic testing is unfortunately
of less benefit, despite much work. Lung cancer is the
leading cause of cancer death in men and women, and
an external factor, cigarette smoking, is its number
The Future of Dive Medicine
RESEARCH, EDUCATION & MEDICINE
EXPERT OPINIONS
50
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WINTER 2016
By Petar Denoble, M.D., D.S.C.
HOW SCIENTIFIC RESEARCH WILL ENHANCE DIVER SAFETY
Genetic testing facilitates precision medicine,
which has improved breast cancer treatment.
Decompression sickness, like breast cancer,
may be promoted by particular genetic or
epigenetic variables, which if better understood
could lead to precision medicine for divers.
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