Colorectal cancer is the second most common cancer in the United States. The average person’s lifetime risk of developing it is about one chance in 20 (6%). The risk is increased if there is a family history of colorectal polyps or cancer, and is still higher if there is a personal history of breast, uterine, or ovarian cancer. Risk is also higher for people with a history of extensive inflammatory bowel disease, such as ulcerative or Crohn’s colitis. It is estimated that 14% of all cancers diagnosed each year occur in the colon or rectum. In 2001, approximately 140,000 new cases will be diagnosed and 56,000 people will die from this disease.
WHO IS AT RISK
Although colorectal cancer may occur at any age, more than 90% of these
tumors occur in people over the age of 40. The risk increases with
age. Certain factors are associated with higher risks including personal
history of breast, uterine or ovarian cancer; inflammatory bowel disease;
a family history of polyps or colorectal cancer.
HOW DOES IT START
Most colon and rectal cancers develop from a single cell or group of
cells in the lining of the bowel. These cells start to multiply and
grow into a non-cancerous growth called a polyp. Polyps appear as
elevations or projections on the lining of the bowel wall. As they
increase in size, they may become cancers with the potential to invade
through the bowel wall or spread to other sites in the body. The
change of a benign polyp into a cancerous tumor appears to be associated
with changes or mutations in the genes that control each cell.
WHAT ARE THE SYMPTOMS
Many polyps and cancers of the colon and rectum do not produce symptoms
until they become fairly large. When symptoms occur, they may be
attributed to other common disorders such as hemorrhoids. The most
common symptom is bleeding with bowel movements (blood in the stool, toilet
water, or on the toilet tissue). Changes in bowel habits, such as
new problems with constipation or persistent diarrhea are good reasons
to see your doctor for evaluation. Abdominal pain and unexplained
weight loss may be symptoms of more advanced cancers.
HOW CAN YOU PREVENT COLORECTAL CANCER
Although colorectal polyps and cancers may not produce symptoms early
in their development, simple screening methods can detect many growths
or polyps early. Finding and removing colorectal polyps clearly reduces
the risk of their developing into cancers.
Diet plays a role, although how big a role is not clear. A high-fiber, low-fat diet will likely reduce your overall risk of developing cancer.
WHEN SHOULD YOU BE CHECKED
Please see our screening colonoscopy page.
HOW IS COLORECTAL CANCER TREATED
Colon cancers are removed surgically. An operation is usually
performed through an abdominal incision. The section of bowel containing
the cancer along with the associated blood vessels and lymph nodes are
removed. In most cases, the bowel is put back together or reconnected
so that normal bowel function is restored. If the cancer has spread
to the lymph nodes or elsewhere, additional treatment such as chemotherapy
and/or radiation therapy may be suggested.
Cancers of the rectum develop in the lower six inches of the bowel above the anus. There are more options for treating these tumors. Most of the larger cancers are surgically removed through the abdomen. Larger, non-cancerous polyps and some early cancers may be removed through the anus. As with colon cancer, additional treatment of chemotherapy or radiation therapy may be required. This may be given before or after the surgery.
STAGING
Staging is a way to estimate the chance of a cure after a cancer has
been removed. Unlike other solid tumors, the size of the colorectal
cancer has little influence on the possibility of a cure. Staging
helps the doctor evaluate the tumor based on: if it has grown into the
bowel wall; if it has spread into nearby lymph nodes; and, if it has spread
to distant organs or tissues. Staging is important because it can
help predict chances of survival and guide additional treatments.
The appearance of tumor cells under the microscope is also significant
in determining treatment. This is called differentiation. Staging
and differentiation help physicians decide whether to recommend radiation
therapy and/or chemotherapy in addition to surgery.
LONG-TERM OUTCOME AFTER TREATMENT
If a colorectal cancer recurs, it will usually do so within two years.
The vast majority recur within five years. Estimates of long-term
cure are based on the stage of the disease. Patients with early cancers,
which have not gone through the bowel wall and have not spread to the lymph
nodes or elsewhere, have an excellent outlook. When the cancer has
spread to other areas or involves the lymph nodes, the chance of cure may
be significantly improved by additional surgery and/or chemotherapy or
radiation therapy.
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