Encyclopedia of Health and Medicine

C
cancer risk factors The circumstances that may
increase an individual’s chance for developing
cancer. Cancer risk is a combination of hereditary,
environmental, viral, bacterial, immunologic, and
lifestyle factors that alter CELL STRUCTURE AND FUNC-
TION. Age is the most significant single risk factor
for cancer, with most cancer developing in people
age 50 and older. This reflects current thinking
that most cancer results from cumulative damage
to cellular DNA, which causes changes in cells as
they divide.
Gender is a significant risk factor for specific
cancers. For example, BLADDER CANCER is three
times more common in men than women, and
only about 1 percent of BREAST CANCER occurs in
men. Ovarian and endometrial cancers are
uniquely women’s cancers, and TESTICULAR CANCER
and PROSTATE CANCER are uniquely men’s cancers.
LIVER CANCER and PANCREATIC CANCER are also more
common in men. Hereditary genetic factors influence
the risk for breast cancer, ovarian cancer, and
COLORECTAL CANCER.
The most significant mutable (changeable) risk
factor for cancer is cigarette smoking, which
accounts for 85 percent of LUNG CANCER, 60 percent
of bladder cancer, and about 30 percent of other
cancers collectively. Excessive ALCOHOL consumption
and exposure to environmental carcinogens
(substances that cause cancer) are also preventable
risks for cancer.
Infectious agents are emerging as major risk
factors for certain cancers. Researchers have
already linked certain cancers with specific infections.
More than 90 percent of women who have
CERVICAL CANCER also have HUMAN PAPILLOMAVIRUS
(HPV) INFECTION. About 80 percent of people who
have STOMACH CANCER test positive for the presence
of HELICOBACTER PYLORI, which causes a low-grade
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bacterial infection in the stomach. In Western cultures,
KAPOSI’S SARCOMA occurs nearly exclusively
in people who have HIV/AIDS.
See also BACTERIA; BRCA-1/BRCA-2; CANCER PRE-
VENTION; COLONOSCOPY; MAMMOGRAM; PARASITE;
PROSTATE-SPECIFIC ANTIGEN (PSA); SMOKING AND
HEALTH; VIRUS.
cancer treatment options and decisions The
methods and protocols available to treat cancer
and its symptoms. Most cancer treatment involves
a combination of methods. There are a number of
conventional treatment options for cancer:
• SURGERY FOR CANCER, in which the doctor performs
an OPERATION to remove the cancer, is the
treatment of first choice for most solid tumors
(cancer that develops in organs and tissues
other than the BLOOD, LYMPH, or BONE MARROW).
The surgery generally removes the tumor and a
safe margin of healthy tissue surrounding the
tumor in the attempt to prevent stray cells at
the tumor’s periphery from migrating into
other tissues. Sometimes the operation to
remove the cancer involves removing an entire
structure or organ to obtain such a margin.
• RADIATION THERAPY may precede or follow surgery
or may be the sole or an adjuvant treatment.
Radiation therapy targets high-energy
particles at the cancer cells. The energy—radiation—disrupts
the ability of the cancer cells to
grow and divide. The cells die, and the body’s
natural mechanisms (such as PHAGOCYTOSIS)
eliminate their debris. Radiation before surgery
shrinks the tumor. The main purpose of radiation
therapy after surgery is to kill any lingering
or stray cancer cells. The oncologist may also
combine radiation therapy with CHEMOTHERAPY