As the second most
common cause of death among Americans, cancer is expected
to cause more than 550,000 deaths in the year 2000.
Cancer Basics
The term cancer actually refers to more than 100 diseases.
What they all have in common is the uncontrolled growth
and spread of cells that have become abnormal.
Cells dividing to produce more cells is basic to your
body's continued health. However, when new cells that
your body doesn't need are produced, they can form a
mass of tissue called a tumor. Some tumors are benign,
meaning that they aren't cancerous.
Malignant tumors are cancerous. They can invade and
damage tissues and organs located near the primary tumor.
Cells can also break off from the original tumor and
travel to other parts of the body, where they form new
tumors -- a process called metastasis.
How Does Cancer Develop?
The initiation phase of cancer consists of damage to
the genetic material, called DNA (deoxyribonucleic acid),
found in cells. Initiation typically is caused by a
carcinogen --anything that can damage cells in a way
to make them cancerous.
Carcinogens activate special genes, known as oncogenes,
present in the cells. Oncogenes normally control cell
growth and multiplication. When activated by a carcinogen,
however, oncogenes initiate and continue the conversion
of normal cells into cancer cells.
Another genetic change that can lead to cancer is the
suppression or loss of tumor-suppressor genes, which
normally produce proteins to inhibit cell division.
Potentially cancerous cells are being formed in the
body at anytime under certain circumstances. Why doesn't
everyone develop cancer, then? For one thing, the immune
system destroys many abnormal cells before they have
a chance to multiply.
Another way the body gets rid of old or damaged cells
is called apoptosis. Each cell has a life span programmed
into its DNA and divides a specified number of times
before it naturally dies. This programmed cell death
regulates the number of cells in tissues and eliminates
many potentially dangerous cells in the body, including
cancer cells.
Cancer may occur when some abnormal cells escape these
safeguards. In the second phase of cancer, called promotion,
abnormal cells are stimulated to grow and multiply to
establish cancer.
Who Is at Risk of Cancer?
Virtually everyone-men, women, and children- is at some
risk of developing cancer. Cancer risk increases with
age. Almost 80% of all cancers are diagnosed in people
aged 55 and older.
A small percent of cancers are hereditary, that is,
the malfunction of the oncogene is inherited. However,
the vast majority of cancers result from damage done
by carcinogens. Here are some major risk factors for
cancer.
Risk Factors
| Exposure to tobacco smoke and/or
smokeless tobacco |
Smoking accounts for 85% of lung
cancer deaths. |
| Diet |
High-fat diet may be linked to cancers
of the breast, colon, uterus, and prostate. |
| Overweight and obecity |
Serious overweight appears to be
linked to increased risk of cancers of the prostate,
pancreas, uterus, colon, ovary, and breast (in older
women). |
| Exposure to ultraviolet radiation |
Ultraviolet radiation from sunlight,
sunlamps, and tanning booths can cause skin cancer. |
| Alcohol use |
Drinking large amounts of alcohol
may increase the risk of cancer of the mouth, throat,
esophagus, and larynx (especially in a cigarette
smoker), the liver, and, possibly, the breast. |
| Radiation |
Exposure to large doses of radiation
from medical X-rays may increase cancer risk. |
| Chemicals and other substances in
the workplace |
Exposure to certain metals, dust,
chemicals, or pesticides can increase cancer risk.
Known carcinogens include asbestos, nickel, cadmium,
uranium, radon, vinyl chloride, benzene, and benzidene.
|
| Hormone replacement therapy |
Estrogen alone increases the risk
of uterine cancer; adding progesterone reduces this
risk. High doses or long-term use of estrogen both
appear to increase breast cancer risk. |
| Diethylstilbestrol (DES) |
Some daughters of women given DES
during pregnancy have an increased risk of developing
abnormal cells in the vagina and cervix. |
| Family History |
A few cancers, including cancers
of the breast, ovary, and colon and melanoma, tend
to run in families. |
| Viruses |
Certain cancers are known to be
related to viral infections. |
Adopted from references 1 and 2.
References
View cancer
references list.
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