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What Is Colorectal
Cancer?
Colorectal cancer is the
third most common non-skin cancer diagnosed in men and women in the U.S. It is
also the second highest cause of cancer deaths. Still, colorectal cancer is
highly curable when it is detected early enough. Colorectal cancer is a result
of cancer cells that form in the lining of the colon (large intestine) or
rectum.
How Colorectal Cancer Starts
Colorectal
cancer often begins as a benign growth known as a polyp. Adenomas are a type of
polyp and are benign tumors of the tissue lining the colon or rectum. Most
polyps will stay benign, but some adenomas have the potential to turn into
cancer over the long term. If they are removed early, this prevents them from
turning in to cancer.
Risk Factors You Can't
Control
Some risk factors for
getting colorectal cancer are beyond your control. The following all increase
the risk of getting colorectal cancer:
·
Inflammatory bowel
disease
·
Colon polyps
·
Age over 50
·
Family history of
colorectal cancer
·
History of breast or
ovarian cancer
Risk Factors You Can
Control
However, there are other
risk factors for colorectal cancer that you can control. The following risk
factors can be modified:
·
Eating a diet high in
red or processed meat, or eating meat cooked at high temperatures
·
Overweight or obesity
·
Inadequate exercise
·
Cigarette smoking
·
Drinking alcohol
Warning Signs of Colorectal Cancer
Screening is
important because colorectal cancer in its early stages usually doesn't produce
any symptoms. Screening can detect the cancer before it produces symptoms, when
it is most curable. After the disease begins to spread, it can produce blood in
the stool, changes in bowel patterns (like diarrhea or constipation), abdominal
pain, weight loss, or fatigue. Tumors that cause symptoms are typically larger
and harder to treat.
Screening for Colorectal Cancer
It is
recommended that most people have a screening colonoscopy every 10 years
starting at age 50. A colonoscopy allows examination of the entire colon and
rectum using a tiny camera. This test can find cancers in the early, most
treatable stage and actually prevent cancers from developing by removing
polyps, as shown here.
What Is a Virtual Colonoscopy?
An alternative
to colonoscopy uses CT scan images to visualize the colon. This is known as a
virtual colonoscopy. As with a conventional colonoscopy, the colon must be
emptied as thoroughly as possible prior to the examination. In virtual
colonoscopy, polyps or tumors are visualized without inserting the camera into
the intestine. One disadvantage is that a virtual colonoscopy can only identify
and not remove any polyps that are found. A real colonoscopy is needed to
remove polyps that may be identified.
Colon X-Rays (Lower GI)
An X-ray of the
colon, known as a lower GI series, can provide another way to image the colon
and rectum. A chalky liquid known as barium is used as a contrast agent. This
photo shows an example of an "apple core" tumor that narrows the
colon. As with a virtual colonoscopy, a real colonoscopy or other surgical
procedure would be needed to remove any tumors or polyps that may be found.
Colorectal Cancer Diagnosis
If there are abnormalities seen in your colon or rectum, a biopsy
is done to determine whether cancer is present. This can be done during a
colonoscopy. The tissue is examined microscopically to look for cancer cells.
This picture shows a highly magnifColorectal
Cancer Staging
Staging is the process
of determining how far a tumor has spread beyond its original location. Staging
may not be related to the size of the tumor. Treatment decisions also depend
upon the stage of a tumor. Staging for colorectal cancer is as follows:
·
Stage 0 – The cancer is
found only in the innermost lining of the rectum or colon.
·
Stage I – The cancer has
not spread beyond the inner wall of the rectum or colon.
·
Stage II – The cancer
has spread into the muscle layer of the rectum or colon.
·
Stage III – The cancer
has spread to at least one lymph node in the area.
·
Stage IV – The cancer
has spread to distant sites in the body, such as the bones, liver, or lungs.
This stage is NOT dependent on how far the tumor has penetrated or if the
cancer has spread to lymph nodes near the tumor.
Survival Rates for Colorectal Cancer
Higher stages
mean that a cancer is more serious and has a worse prognosis. Patients with
stage I colorectal cancer have a 5-year survival rate of 74%, while that rate
drops to 6% for Stage IV tumors.
Colorectal Cancer Surgery
Except for very
advanced cases, colorectal cancer is usually treated by surgically removing the
tumor and surrounding tissues. Surgery has a very high cure rate for early
stage tumors. For advanced tumors that have spread outside the colon, surgery
does not typically cure the condition, but removing larger tumors may reduce
symptoms.
Advanced Colorectal Cancer Treatment
Colorectal
cancer that has spread to the lymph nodes (stage III) can sometimes still be
cured. In this case treatment usually consists of surgery and chemotherapy for
colon cancer. In cases of rectal cancer, radiation therapy is added both prior
to and following surgery in more advanced cases. Cancers that return after
treatment or spread to other organs are harder to treat and more difficult to
cure, but treatments may relieve symptoms and prolong life.
Coping With Chemotherapy
Modern
chemotherapy drugs are less likely to cause nausea and other troubling side
effects than older drugs, and medications are also available to help control
these side effects. Clinical trials are always underway to develop better and
more tolerable chemotherapy drugs.
Radiofrequency Ablation
Radiofrequency
ablation (RFA) is a kind of cancer treatment that uses heat to destroy tumor
tissue. CT scanning is used to guide insertion of a needle-like device into the
tumor, through which intense heat is applied. RFA can be an option for
destroying tumors that cannot be removed by surgery. In patients who have a few
metastatic tumors in the liver that cannot be removed by surgery, chemotherapy
is sometimes combined with RFA to destroy the tumors.
Colorectal Cancer Prevention: Diet
Eating a
nutritious diet, getting enough exercise, and controlling body fat could
prevent 45% of colorectal cancers, according to researchers. This means that
adopting a healthy lifestyle can dramatically lower your risk of getting
colorectal cancer. The National Cancer Institute recommends a diet low in fat
with plenty of fiber and at least five servings of fruits and vegetables each
day.
Preventing Cancer With Exercise
One study
showed that people who got the most physical exercise were 24% less likely to
get colorectal cancer than their least active counterparts. There was no
difference if this activity was related to work or recreation. The American
Cancer Society recommends at least 30 minutes of exercise a day for 5 or more
days a week.
Reviewed by Melissa Conrad Stöppler, MD on Saturday, July 16, 2016
Bladder Cancer Symptoms, Stages, Treatments
This tool does not provide medical advice.
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