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 CANCERoccurs in
men. Ovarian and endometrial cancers are
uniquely women’s cancers, and TESTICULAR CANCER
and PROSTATE CANCERare uniquely men’s cancers.
LIVER CANCERand PANCREATIC CANCERare also more
common in men. Hereditary genetic factors influ-
ence 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 ALCOHOLconsump-
tion and exposure to environmental carcinogens
(substances that cause cancer) are also preventa-
ble risks for cancer.
Infectious agents are emerging as major risk
factors for certain cancers. Researchers have
already linked certain cancers with specific infec-
tions. More than 90 percent of women who have
CERVICAL CANCERalso have HUMAN PAPILLOMAVIRUS
(HPV) INFECTION. About 80 percent of people who
have STOMACH CANCERtest positive for the presence
of HELICOBACTER PYLORI, which causes a low-grade

bacterial infection in the stomach. In Western cul-

tures, KAPOSI’S SARCOMAoccurs 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 per-

forms an OPERATIONto remove the cancer, is the

treatment of first choice for most solid tumors

(cancer that develops in organs and tissues

other than the BLOOD, LY M P H, 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 THERAPYmay precede or follow sur-

gery or may be the sole or an adjuvant treat-

ment. Radiation therapy targets high-energy

particles at the cancer cells. The energy—radia-

tion—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 radia-

tion therapy after surgery is to kill any lingering

or stray cancer cells. The oncologist may also

combine radiation therapy with CHEMOTHERAPY

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