Download The Cancer Process - American Institute for Cancer Research

Facts on
Preventing Cancer
The Cancer Process
The Cancer Process
How does the transformation of a single cell
into cancer occur? And how does your body
work to slow the cancer process down?
This brochure explains what cancer is
and what you can do to protect yourself
against it.
Throughout our lives, everyday habits – such
as what we eat, whether we smoke and how
active we are – all contribute to our risk
of developing cancer. The more unhealthy
lifestyle factors we engage in, the greater
likelihood that our cells can sustain damage
that leads to cancer.
This brochure is based on the AICR/
WCRF expert report, Food, Nutrition,
Physical Activity, and the Prevention of
Cancer: a Global Perspective, and its
ongoing review and update through our
Continuous Update Project (CUP).
The expert report was written by a panel
of leading scientists and researchers who
reviewed all the available evidence on diet,
physical activity and weight management
in relation to cancer prevention and
survivorship. The expert report contains
recommendations that scientists estimate
could help prevent about one-third of the
most common cancers, such as colon and
breast cancer. (See page 14 for the full list
of AICR Recommendations for Cancer
Prevention.)
Words in blue boldface type appear in the Glossary
on page 10.
What is Cancer?
Cancer originates at the cell level. Cells are the
basic building blocks of our body.
Every cell contains genetic
information (DNA), which
controls its functions.
The body is made up of
many types of cells that
compose different organs.
Normally, these cells grow and
divide in a controlled way to produce more
cells as they are needed to keep the body
healthy. When cells become old or damaged,
they are “programmed” to die and are
replaced with new cells.
Cancer occurs when abnormal cells divide
without stopping because of permanent
changes, called mutations, in DNA. These
abnormal cancer cells do not die when
they should and new cells form and grow
uncontrolled. Cancer cells often form a mass
called a tumor.
Not all tumors are cancerous;
tumors can be benign or
malignant.
• Benign tumors aren’t
cancerous. They are
different from malignant
tumors because they do not spread to other
parts of the body. They are slow growing
as opposed to rapidly growing cancerous
tumors, and the edges of their cells are clearly defined.
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Benign tumors can often be removed;
examples are moles and uterine fibroid
tumors. In most cases, they do not come
back.
• Malignant tumors are cancerous. Cells in
these tumors change shape and
grow rapidly. They can invade
nearby tissues and spread
to other parts of the body.
The spread of cancer
from one part of the
body to another is called
metastasis.
There are more than 100
different types of cancer. Most
are named for the organ or type of cell in
which they start.
The main categories of cancer include:
• Carcinoma - cancer that begins in the skin or in tissues that line or cover internal organs.
• Sarcoma - cancer that begins in bone, cartilage, fat, muscle, blood vessels or other connective or supportive tissue.
Whether cancer cells divide quickly or slowly,
they ultimately disrupt the normal structure
and function of the body’s normal tissue.
Cancers are capable of spreading throughout
the body by two mechanisms: invasion and
metastasis.
• Invasion refers to the direct migration and
penetration by cancer cells into neighboring
tissues.
• Metastasis refers to the condition where
cancer cells circulate through the
bloodstream and then invade normal tissues
elsewhere in the body.
When cancer is found, a doctor will determine
what type it is and how fast it is growing. He
or she will also determine whether cancer cells
have invaded nearby healthy tissue or spread
(metastasized) to other parts of the body.
In some cases, finding cancer early may
decrease a person’s risk of dying from the
cancer. For this reason, improving screening
methods for early detection is currently a high
priority for cancer researchers and healthcare
providers.
• Leukemia - cancer that starts in blood-
forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood.
• Lymphoma and myeloma - cancers that begin in the cells of the immune system.
• Central nervous system cancers - cancers that begin in the tissues of the brain and spinal cord.
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What Causes Cancer?
The DNA of a cell can become damaged or
changed by external factors in the environment
or by inherited genes.
Healthy Cell
•Obesity
•Healthy,
stable weight
•Diet low in
vegetables,
fruits, whole grains and
beans
•Plenty of
vegetables,
fruits, whole
grains and
beans
•High red and
processed
meat
consumption
•At least
30 minutes
of moderate
activity each day
•Lack of
physical
activity
•Breastfeeding
•Excessive
alcohol and sodium
consumption
It usually takes years, even decades, for DNA
damage to turn into cancer. Many changes
need to occur for the disease to develop. But
there are steps you can take now to prevent,
delay or even stop the cancer process.
For example:
•
Don’t smoke or chew tobacco.
Smoking by itself causes 90 percent of lung cancer deaths among men and 80 percent of lung cancer deaths
among women; and 40 percent of
all cancers.
•
Maintain a healthy weight for you. After not smoking, being a healthy weight is the most important way
you can reduce your risk of cancer.
Extra fat tissue, especially around the
waist, is an indicator of higher risk of cancer
(see “Inflammation,” on p. 7).
•
Limit alcohol. Drinking alcohol
can cause cancers of the breast, colorectum (in men), mouth,
throat, esophagus and liver.
•
Avoid processed meats (such as
hot dogs, bologna, sausage, bacon and ham). They are strongly linked to risk for colon cancer, as is eating
more than 18 ounces of cooked red
meat (including beef, pork and lamb)
per week.
Genetic Causes
Healthy Cell
Cancer Cell
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Only 5-10 percent of all cancers are associated
with having a family history of cancer. People
who inherit these genes do have a higher
cancer risk, but may never develop the disease.
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If you have a family history of cancer and
are concerned, it’s important to consult your
healthcare provider and get regular screenings.
Environmental factors
Known environmental cancer risks include:
• Too much exposure to
the sun
• Cigarette smoke (including second
hand smoke)
• Certain industrial
chemicals affecting workers
with high exposures to them
Many environmental factors such as pollution
and cigarette smoke contain carcinogens.
They also create molecules called “free
radicals.” These molecules occur naturally
inside the body as we age. Although these
molecules do some good, too many may cause
damage that increases cancer risk. Plant-based
foods – vegetables, fruits, whole grains and
beans – contain vitamins and phytochemicals
that often act as “antioxidants,” which can
protect the cell and DNA from damage due to
free radicals.
Radiation therapy
Infectious diseases
Several viruses lead to certain cancers: Epstein
Barr virus in esophageal cancer, Helicobacter
pylori virus in stomach cancer, hepatitis B and
C viruses in liver cancer, and Human papilloma
virus in cervical cancer.
Inflammation
Although acute inflammation
is the body’s response to
infection or injury and is
essential to healing, too
much constant, or chronic,
inflammation can damage cells
and their DNA. Because fat cells
constantly make certain proteins that can lead
to inflammation, overweight and obesity are
strongly tied to higher cancer risk, as well as
heart disease and diabetes.
Insulin resistance
This condition occurs when cells do not respond
properly to insulin, a hormone produced by the
pancreas that helps cells take in and use glucose
(a form of sugar in the blood that increases
after we eat) needed to produce energy. The
body tries to make up for this by producing
more insulin. If untreated, insulin resistance can
lead to Type 2 diabetes and is associated with
increased risk of some cancers.
If you have had radiation therapy in the past,
it may have put you at higher risk for other
cancers. Radiation therapy for cancer can
damage DNA and increase the number of
mutations affecting cells.
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What Protects Us
from Cancer?
A healthy diet and adequate physical activity
reduce cancer risk. AICR/WCRF’s expert panel
estimates that approximately one-third of the
most common cancers could be prevented if
everyone followed the AICR Guidelines for
Cancer Prevention:
•
Choose mostly plant foods, limit red meat and avoid processed meat, as well as highly processed foods and beverages with added sugar and fat.
For protection from cancer,
eat an abundant variety of
vegetables, fruits, whole
grains and beans. Plant
foods contain vitamins,
minerals, fiber, antioxidants and
phytochemicals (naturally occurring
compounds) that block the beginning and
growth of cancer.
• Be physically active every day in any way for 30 minutes or more. Strong scientific
evidence shows that physical
activity protects against
colon cancer and probably
protects against breast and
endometrial cancers. Physical
activity reduces excess
levels of hormones that may
stimulate cancer growth. AICR
recommends moving often during
the day to avoid being sedentary for too long.
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• Aim to be a healthy weight throughout life.
Obesity and overweight are linked to
postmenopausal breast cancer, colon cancer
and cancers of the endometrium, esophagus,
gallbladder, kidney and
pancreas. Excess body fat
Visit www.aicr.org
can raise hormone levels,
for plenty of great ideas
including substances
for healthy foods,
called “growth factors”
physical activity and
that may speed up the
weight management
cancer process. Prevent
advice.
weight gain by controlling
portion sizes, eating foods
that are lower in calories and getting regular
physical activity.
• And always remember − do not smoke or chew tobacco.
Smoking is the single most common cause
of cancer, according to the National Cancer
Institute.
YOU are in control of many of the most
important cancer risk factors. For more
information, visit www.aicr.org.
For mothers and their babies,
breastfeeding has many
benefits, including protection
against cancer. Breastfeeding
reduces the levels of some
hormones linked to cancer,
such as estrogen. Babies who are
breastfed are less likely to become
overweight and obese later in childhood. It
is best for mothers to breastfeed their babies
exclusively for the first six months of life.
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Glossary
Antioxidants - Substances that can protect the
cell and DNA from the damage caused by free
radicals.
Benign - Harmless; describes a non-cancerous
tumor.
Carcinogen - Any substance that can cause
cancer. Used to describe compounds that
increase the risk of getting cancer by damaging
DNA directly in the cell.
Cell - Basic structural and functional building
block of our body and other living organisms.
DNA - Deoxyribonucleic acid, the carrier of
genetic information, present in every cell of the
body.
Epstein Barr virus - A member of the herpes
virus family that can lead to esophageal cancer.
Free radicals - Harmful molecules created in
the body as a byproduct of normal cellular
activity. Environmental factors such as
pollution and cigarette smoke can also produce
free radicals. If produced in large numbers,
they can start a chain reaction, which leads to
cellular and DNA damage.
Growth factors - Substances in the body
that increase cellular growth. Some are
necessary for proper human growth. In some
circumstances, however, they can stimulate
cancer growth.
Helicobacter pylori - A bacterium, also known
as H. pylori, that causes inflammation and
damage to cells lining the stomach and small
intestine and is a known cause of stomach
cancer.
Hormones - Substances that are secreted by
cells or glands in our bodies and facilitate
several functions. However, high levels of
certain hormones can raise cancer risk.
Examples of hormones include estrogen,
androgen and testosterone, growth factors and
insulin, which is produced in the pancreas to
regulate the amount of glucose (sugar) in the
blood.
Human papilloma virus - An established cause
of cervical cancer.
Inflammation - The body’s response to external
injury and an attempt to heal tissues. Acute
inflammation is helpful in limiting infections.
Chronic inflammation can damage DNA and
create a favorable environment for cancer
growth.
Insulin resistance - Condition in which
the body produces insulin but cells cannot
effectively respond to it. Insulin is a hormone
necessary for cells to use blood sugar. If
untreated, this condition can lead to Type 2
diabetes. Also associated with increased risk of
some cancers.
Invasion - The direct migration and penetration
by cancer cells into neighboring tissues.
Malignant - Harmful; describes a cancerous
tumor.
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Metastasis - Process by which cancer breaks off
from the initial site and spreads to other areas
in the body.
Mutation - Change in the genetic material
(DNA) of the cell, which can be inherited or
occur after birth.
NEED MORE HELP?
Visit www.aicr.org for more information
about diet, physical activity, weight and cancer
prevention and survivorship. Or call 1-800843-8114 to request additional brochures (up
to three individual copies), such as:
Phytochemicals - Biologically active
compounds found in plant foods, which can
prevent, delay or interrupt the cancer process
in many ways.
• 10 Ways to Reduce Your Cancer Risk
• Eat Well for Life
• Move More for Life
Tumor - Mass of tissue formed by a new
growth of cells. Malignant tumors are called
cancers and are caused by uncontrolled cell
division.
• Reach Your Healthy Weight for Life
• The New American Plate
These and other brochures with recipes can be
downloaded for free at www.acir.org. You can
also visit the AICR Hotline online for answers
to your questions about diet and cancer, or call
1-800-843-8114 Monday-Friday, 9 am-5 pm
ET. A registered dietitian will return your call.
Contact us at:
American Institute for Cancer Research
1759 R Street, NW, P.O. Box 97167
Washington, DC 20090-7167
1-800-843-8114 or 202-328-7744
email: [email protected]
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AICR Recommendations for Cancer Prevention
Editorial Review Committee
1. Be as lean as possible without becoming underweight.
Elisa V. Bandera, MD, PhD, The Cancer Institute of New
Jersey, UMDNJ-Robert Wood Johnson Medical School;
Karen Collins, MS, RD, CDN, Nutrition Consultant; John
Erdman, Jr., PhD, University of Illinois; Lidia Schapira,
MD, Dana-Farber/Harvard Cancer Center; Amy L.
Yaroch, PhD, Gretchen Swanson Center for Nutrition,
University of Nebraska Medical Center; AICR executive
staff.
2. Be physically active for at least 30 minutes every day.
3. Avoid sugary drinks. Limit consumption of energy-dense foods (particularly processed foods high in added sugar, or low in fiber, or high in fat).
4. Eat more of a variety of vegetables, fruits, whole grains and legumes such as beans.
AICR is part of the World Cancer Research Fund global
network, which consists of the following charitable
organizations: the umbrella association, World Cancer
Research Fund International (WCRF International);
the American Institute for Cancer Research (AICR);
World Cancer Research Fund (WCRF UK); World Cancer
Research Fund Netherlands (WCRF NL); and World
Cancer Research Fund Hong Kong (WCRF HK).
5. Limit consumption of red meats (such as beef, pork and lamb) and avoid processed meats.
You can support AICR’s life-saving research
and education efforts in a variety of ways:
6. If consumed at all, limit alcoholic drinks to two for men and one for women a day.
7. Limit consumption of salty foods and foods processed with salt (sodium).
8. Don’t use supplements to protect against cancer.
Special Population Recommendations
9. It is best for mothers to breastfeed exclusively for up to six months and then add other liquids and foods.
• Make a donation online at www.aicr.org;
• Write to AICR, 1759 R Street, NW,
P.O. Box 97167, Washington, DC
20090-7167; or
• Include a bequest in your will.
or more information, contact our Gift
F
Planning Department at 1-800-843-8114.
10.After treatment, cancer survivors should
follow the recommendations for cancer
prevention.
And always remember – do not smoke or chew
tobacco.
Copyright © 2013 American Institute for Cancer Research
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AICR Guidelines for Cancer Prevention
The choices you make about food, physical
activity and weight management can reduce
your chances of developing cancer.
●Choose
mostly plant foods, limit red meat
and avoid processed meat.
●Be
physically active every day in any way
for 30 minutes or more.
●
Aim to be a healthy weight throughout life.
And always remember–do not smoke or
chew tobacco.
About AICR
The American Institute for Cancer Research (AICR) is
the cancer charity that fosters cancer prevention and
survivorship through healthy diets, physical activity and
body weight. About one-third of the most common cancers
could be prevented this way. By raising awareness of this
message, we hope that many thousands of lives will be
saved. The education and research programs of AICR are
funded almost entirely by donations from the public.
We fund cutting edge cancer research and help people make
choices that reduce their changes of developing cancer. We
are part of a global network of charities that are committed
to preventing cancer.
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