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Colon and rectal
cancer develop in the digestive tract, which is also called the gastrointestinal,
or GI, tract. The digestive system processes food for energy and rids the
body of solid waste matter. Cancer can develop in any of the four sections
of the colon or in the rectum.
Colorectal cancers are thought to develop slowly over a period of several
years. Before a true cancer develops, there usually are precancerous changes
in the lining of the colon or rectum. These changes might be dysplasia
(abnormal cells) or adenomatous polyps. A polyp is a growth of tissue into
the center of the colon or rectum.
More than 95 percent of colorectal cancers are adenocarcinomas. These
are cancers of the glandular cells that line the inside of the colon and
rectum. Other less common types of tumors found in the colon and rectum
include:
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Carcinoid tumors: tumors of hormone-producing cells of the intestine,
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Gastrointestinal stromal tumors: tumors of the connective tissue in the
wall of the colon and rectum, and
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Lymphomas: cancers of the immune cells in the colon and rectum, lymph nodes,
and other organs.
The treatment and prognosis (outlook) for these rarer types of tumors differs
from that of adenocarcinoma.
About 94,700 new cases of colon cancer (43,000 men and 51,700 women)
and 34,700 new cases of rectal cancer (19,400 men and 15,300 women) are
expected to be diagnosed in 1999 in the US. Colon cancer is expected to
cause about 47,900 deaths (23,000 men and 24,900 women) this year, and
about 8,700 people (4,800 men and 3,900 women) will die from rectal cancer.
The number of people dying from colorectal cancer has been going down
for the past 20 years. This may be because there are fewer cases, more
cases are found early, and treatment has improved.
The five-year survival rate is 92 percent for people whose colorectal
cancer is found and treated in an early stage, before it has spread. But,
only 37 percent of colorectal cancers are found at that early stage. Once
the cancer has spread to nearby organs or lymph nodes, the five-year survival
rate drops to 64 percent. For people whose colorectal cancer has spread
to distant parts of the body such as the liver or lungs, the five-year
survival rate is seven percent.
Risk factors for colorectal cancer include:
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A family history of colorectal cancer: If a family member has had colorectal
cancer, talk with your doctor about your individual risk and when screening
tests should begin.
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A personal history of colorectal cancer: Even when a colorectal cancer
has been completely removed, new cancers may develop in other areas of
the colon and rectum.
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A personal history of intestinal polyps: Some types of polyps do not increase
the risk of colorectal cancer, but other types, such as adenomatous polyps,
do increase the risk of colorectal cancer, especially if they are large
or numerous.
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A personal history of chronic inflammatory bowel disease: Chronic inflammatory
bowel disease (ulcerative colitis or Crohn’s disease) is a condition in
which the colon is inflamed over a long period of time and may have ulcers
in its lining.
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Aging: About 90 percent of people found to have colorectal cancer are older
than 50.
The American Cancer Society (ACS) recommends men and women at average risk
begin screening for colorectal cancer at age 50 and to follow one of the
following three examination schedules: a fecal occult blood test every
year and a flexible sigmoidoscopy every five years; colonoscopy every 10
years; or a double-contrast barium enema every five to 10 years. A digital
rectal examination should be done whenever the sigmoidoscopy, colonoscopy,
or double-contrast barium enema is performed.
The three main types of treatment for colon cancer are surgery, radiation
therapy, and chemotherapy. Depending on the stage of the cancer, two or
even three of these types of treatment may be combined at the same time
or one after another.
ACS News Center stories are provided as a source of cancer-related
news and are not intended to be used as
press releases.
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