How does colorectal cancer develop?
All of the body’s cells normally grow, divide, and then die in order to keep
the body healthy and functioning properly. Sometimes this process gets out of
control: cells keep growing and dividing even when they are supposed to die.
When the cells lining the colon and rectum multiply uncontrolled, colorectal
cancer may ultimately develop.
Fortunately, most colorectal cancers begin as small
precancerous (adenomatous) polyps. These polyps usually grow slowly and do
not cause symptoms until they become large or cancerous. Colorectal cancer can
be prevented by removing these precancerous polyps. Also, if detected early,
colorectal cancer is potentially curable. That is why it is important to screen
for colorectal polyps and cancer before symptoms develop.
When should screening begin?
Screening for colorectal cancer should begin at the age of 50, when the risk
for developing colorectal polyps and cancer starts to increase. However, if you
have a personal or a family history of colorectal polyps or cancer, screening
should begin at age 40 or even younger in some circumstances. Men and women
should undergo screening since colorectal polyps and cancer affect both genders.
What is involved in screening for colorectal cancer?
Several tests are used to screen for colorectal cancer. The following is a
list of the most common screening tests as well as how often they should be
done. Although colonoscopy — the gold standard — is recommended, other options
are available.
- Colonoscopy — Colonoscopy is the best procedure to check for
colorectal polyps and cancer. It allows for polyps to be removed during the
exam. Colonoscopy is an outpatient procedure in which a physician uses a
long, flexible scope to view the rectum and entire colon. This exam,
performed with a light sedative, requires a bowel preparation to clean out
the colon. It is usually repeated once every 10 years, unless polyps are
found or there is a family history of colorectal polyps or cancer.
- Fecal occult blood test (FOBT) — This is the least accurate
colorectal cancer screening test. The exam — done at home — checks for blood
in the stool, which may be caused by large polyps or cancer. If this test is
the one chosen, it should be done yearly. If blood is detected on any
specimen, a colonoscopy is needed.
- Flexible sigmoidoscopy — This is a brief outpatient procedure,
usually without sedation, in which the inside of the lower large intestine
(the sigmoid colon and rectum) is examined using a short, flexible scope.
This test should be done every 5 years with a yearly FOBT. If polyps are
detected in the sigmoid colon or rectum, then a full colonoscopy should be
performed to look for polyps in the remaining colon.