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Colorectal cancer and polyps
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What
is colon cancer and how is it related to colon polyps?
Colon cancer is a malignant growth starting on the colon lining which
invade into the wall of the colon. It can then spread to lymph nodes or
into the blood stream and then become disseminated (metastatic) to the
liver, lung, bones or brain. Polyps are benign growths on the colon lining.
There is a polyp-cancer sequence for polyps called adenomas. In time there
are progressive alterations to the chromosomes of the polyp’s cells
occur. After a certain degree of genetic changes, these cells can become
malignant and the polyp will turn into a cancer. In this common situation,
these genetic changes are found in the cells of the lesion itself but
not in other cells of the body such as the blood, which can be easily
tested. There a number of conditions, however, where a genetic abnormality
can be found in all of the body’s cells and this includes familial
adenomatous polyposis (FAP), hereditary non-polyposis colon cancer (HNPCC)
and familial colon cancer syndrome in Ashkenazi Jews.
How
common and serious are polyps and cancer?
Benign polyps occur in 30% of people by age 50. The lifetime risk for
colon cancer is 5%. The risk starts at age 40 with marked increase at
50 and the peak at 75. There are 130,000 new cases per year – overall
this is the third most common type of cancer. There are 60,000 deaths
per year and is the second leading cause of cancer deaths.
What
increases the risk for a person to get colon cancer?
Simply getting into middle age represents a significant risk factor for
colon cancer. The highest risk groups for colon cancer include ulcerative
colitis, previous history of polyps or cancer, family history of colon
cancer, certain genetic conditions (familial adenomatous polyposis, hereditary
non-polyposis colon cancer and familial colon cancer syndrome in Ashkenazi
Jews) and a personal history of female cancer. Smoking, drinking and physical
inactivity are additional risk factors for colon cancer.
The family history is more significant with young first-degree relatives
and when multiple family members have had colon cancer. If the relative
was over 55 years old, the risk is double; if the relative was 45-54,
the risk triples; and if the relative was less than 45, the risk quadruples.
How
can colon cancer be prevented?
It has been established that removal of the adenoma polyps can prevent
cancer from developing. There are several ways to screen for polyps and
cancer. The American Cancer Society recommendations for standard risk
individuals 50 years and older are the following: either 1) Stool testing
for occult (chemical traces) blood yearly plus flexible
sigmoidoscopy every 5 years or 2) Colonoscopy
every 10 years. When there is a high risk setting, colonoscopy is the
preferred test. When there is a strong family history of cancer, genetic
counseling and diagnostic testing may also be indicated. Starting on 7/1/01,
Medicare approves of and will pay for colonoscopy every 10 years for standard
risk individuals.
Can
changes in diet and vitamin intake help prevent colon cancer?
The following measures are generally thought to be protective: fat reduction,
increased Fiber intake, increased intake of anti-carcinogens found in
vegetables, fruits, legumes, nuts and grains especially wheat bran (insoluble
fiber) and increased intake of calcium, vitamin E and selenium.
How
are polyps and colon cancer treated?
Polyps are removed during colonoscopy using
electrocautery with snares or biopsy forceps passed through the instrument.
Cancer generally requires surgery. Radiation and chemotherapy are used
when clinically indicated.