Colon Cancer
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Colon cancer is a disease in which malignant (cancer) cells form in the
tissues of the colon.
The colon is part of the body’s digestive system.
The digestive system removes and processes nutrients (vitamins, minerals, carbohydrates,
fats, proteins, and water) from foods and helps pass waste material out of
the body. The digestive system is made up of the esophagus, stomach, and the
small and large intestines. The first 6 feet of the large intestine are called
the large bowel or colon. The last 6 inches are the rectum and the anal canal.
The anal canal ends at the anus (the opening of the large intestine to the
outside of the body).
Age and health history can affect the risk of developing
colon cancer.
Risk factors include the following:
- Age 50 or older.
- A family history of cancer of the colon or rectum.
- A personal history of cancer of the colon, rectum, ovary, endometrium, or breast.
- A history of polyps in the colon.
- A history of ulcerative colitis (ulcers in the lining of the large intestine)
or Crohn's disease.
- Certain hereditary conditions, such as familial adenomatous polyposis and hereditary
nonpolyposis colon cancer (HNPCC; Lynch Syndrome).
- Researchers from Brigham and Women's Hospital and the Harvard School of Public Health have found that women who reported the highest levels of depressive symptoms had a 43% greater risk of developing colorectal cancer than women with the lowest level of symptoms. Furthermore, they observed a "dose-response" relationship, which means that the more depressive symptoms a woman experienced, the higher her risk of developing colorectal cancer. The association was highest among women who were overweight.
Possible signs of colon cancer include a change in bowel habits or blood
in the stool.
These and other symptoms may be caused by colon
cancer or by other conditions. A doctor should be consulted if any of the following
problems occur:
- A change in bowel habits.
- Blood (either bright red or very dark) in the stool.
- Diarrhea, constipation, or feeling that the bowel does not empty completely.
- Stools that are narrower than usual.
- General abdominal discomfort (frequent gas pains, bloating, fullness, or cramps).
- Weight loss with no known reason.
- Constant tiredness.
- Vomiting.
Tests that examine the rectum, rectal tissue, and blood are used to detect
(find) and diagnose colon cancer.
The following tests and procedures
may be used:
- Physical exam and history: An exam of the body to check general signs
of health, including checking for signs of disease, such as lumps or anything
else that seems unusual. A history of the patient’s health habits and past
illnesses and treatments will also be taken.
- Fecal occult blood test: A test to check stool (solid waste) for blood
that can only be seen with a microscope. Small samples of stool are placed
on special cards and returned to the doctor or laboratory for testing.
- Digital rectal exam: An exam of the rectum. The doctor or nurse inserts
a lubricated, gloved finger into the rectum to feel for lumps or abnormal
areas.
- Barium enema: A series of x-rays of the lower gastrointestinal tract.
A liquid that contains barium (a silver-white metallic compound) is put
into the rectum. The barium coats the lower gastrointestinal tract and x-rays
are taken. This procedure is also called a lower GI series.
- Sigmoidoscopy: A procedure to look inside the rectum and sigmoid (lower)
colon for polyps, abnormal areas, or cancer. A sigmoidoscope (a thin, lighted
tube) is inserted through the rectum into the sigmoid colon. Polyps or tissue
samples may be taken for biopsy.
- Colonoscopy: A procedure to look inside the rectum and colon for polyps,
abnormal areas, or cancer. A colonoscope (a thin, lighted tube) is inserted
through the rectum into the colon. Polyps or tissue samples may be taken
for biopsy.
- Biopsy: The removal of cells or tissues so they can be viewed under a
microscope to check for signs of cancer.
- Virtual colonoscopy: A procedure that uses a series of x-rays called computed
tomography to make a series of pictures of the colon. A computer puts the
pictures together to create detailed images that may show polyps and anything
else that seems unusual on the inside surface of the colon. This test is
also called colonography or CT colonography.
Certain factors affect prognosis (chance of recovery) and treatment options.
The prognosis (chance of recovery)
depends on the following:
- The stage of the cancer (whether the cancer is in the inner lining of
the colon only, involves the whole colon, or has spread to other places
in the body).
- Whether the cancer has blocked or created a hole in the colon.
- The blood levels of carcinoembryonic antigen (CEA; a substance in the
blood that may be increased when cancer is present) before treatment begins.
- Whether the cancer has recurred.
- The patient’s general health.
Treatment options depend on the
following:
- The stage of the cancer.
- Whether the cancer has recurred.
- The patient’s general health.
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After colon cancer has been diagnosed, tests are done to find out if cancer
cells have spread within the colon or to other parts of the body.
The process used to find out if cancer has spread
within the colon or to other parts of the body is called staging. The information
gathered from the staging process determines the stage of the disease. It is
important to know the stage in order to plan treatment. The following tests
and procedures may be used in the staging process:
- CT scan (CAT scan): A procedure that makes a series of detailed pictures
of areas inside the body, taken from different angles. The pictures are
made by a computer linked to an x-ray machine. A dye may be injected into
a vein or swallowed to help the organs or tissues show up more clearly.
This procedure is also called computed tomography, computerized tomography,
or computerized axial tomography.
- Lymph node biopsy: The removal of all or part of a lymph node. A pathologist
views the tissue under a microscope to look for cancer cells.
- Complete blood count: A procedure in which a sample of blood is drawn
and checked for the following:
- The number of red blood cells, white blood cells, and platelets.
- The amount of hemoglobin (the protein that carries oxygen) in the
red blood cells.
- The portion of the sample made up of red blood cells.
- Carcinoembryonic antigen (CEA) assay: A test that measures the level of
CEA in the blood. CEA is released into the bloodstream from both cancer
cells and normal cells. When found in higher than normal amounts, it can
be a sign of colon cancer or other conditions.
- MRI (magnetic resonance imaging): A procedure that uses a magnet, radio
waves, and a computer to make a series of detailed pictures of areas inside
the body. This procedure is also called nuclear magnetic resonance imaging
(NMRI).
- Chest x-ray: An x-ray of the organs and bones inside the chest. An x-ray
is a type of energy beam that can go through the body and onto film, making
a picture of areas inside the body.
- Surgery: A procedure to remove the tumor and see how far it has spread
through the colon.
Stage 0 (Carcinoma in Situ)
In stage 0, the cancer is found in the innermost
lining of the colon only. Stage 0 cancer is also called carcinoma in situ.
Stage I
In stage I, the cancer has spread beyond the innermost
tissue layer of the colon wall to the middle layers. Stage I colon cancer is
sometimes called Dukes’ A colon cancer.
Stage II
Stage II colon cancer is divided into stage IIA
and stage IIB.
- Stage IIA: Cancer has spread beyond the middle tissue layers of the colon
wall or has spread to nearby tissues around the colon or rectum.
- Stage IIB: Cancer has spread beyond the colon wall into nearby organs
and/or through the peritoneum.
Stage II colon cancer is sometimes called Dukes'
B colon cancer.
Stage III
Stage III colon cancer is divided into stage IIIA,
stage IIIB, and stage IIIC.
- Stage IIIA: Cancer has spread from the innermost tissue layer of the colon
wall to the middle layers and has spread to as many as 3 lymph nodes.
- Stage IIIB: Cancer has spread to as many as 3 nearby lymph nodes and has
spread:
- beyond the middle tissue layers of the colon wall; or
- to nearby tissues around the colon or rectum; or
- beyond the colon wall into nearby organs and/or through the peritoneum.
- Stage IIIC: Cancer has spread to 4 or more nearby lymph nodes and has
spread:
- to or beyond the middle tissue layers of the colon wall; or
- to nearby tissues around the colon or rectum; or
- to nearby organs and/or through the peritoneum.
Stage III colon cancer is sometimes called Dukes'
C colon cancer.
Stage IV
In stage IV, cancer may have spread to nearby
lymph nodes and has spread to other parts of the body, such as the liver or
lungs. Stage IV colon cancer is sometimes called Dukes’ D colon cancer.
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Different types of treatment are available for
patients with colon cancer. Some treatments are standard (the currently used
treatment), and some are being tested in clinical trials. Before starting treatment,
patients may want to think about taking part in a clinical trial. A treatment
clinical trial is a research study meant to help improve current treatments
or obtain information on new treatments for patients with cancer. When clinical
trials show that a new treatment is better than the “standard” treatment, the
new treatment may become the standard treatment.
Clinical trials are taking place in many parts
of the country. Choosing the most appropriate cancer treatment is a decision
that ideally involves the patient, family, and health care team.
Surgery
Surgery (removing the cancer in an operation)
is the most common treatment for all stages of colon cancer. A doctor may remove
the cancer using one of the following types of surgery:
- Local excision: If the cancer is found at a very early stage, the doctor
may remove it without cutting through the abdominal wall. Instead, the doctor
may put a tube through the rectum into the colon and cut the cancer out.
This is called a local excision. If the cancer is found in a polyp (a small
bulging piece of tissue), the operation is called a polypectomy.
- Resection: If the cancer is larger, the doctor will perform a partial
colectomy (removing the cancer and a small amount of healthy tissue around
it). The doctor may then perform an anastomosis (sewing the healthy parts
of the colon together). The doctor will also usually remove lymph nodes
near the colon and examine them under a microscope to see whether they contain
cancer.
- Resection and colostomy: If the doctor is not able to sew the 2 ends of
the colon back together, a stoma (an opening) is made on the outside of
the body for waste to pass through. This procedure is called a colostomy.
Sometimes the colostomy is needed only until the lower colon has healed,
and then it can be reversed. If the doctor needs to remove the entire lower
colon, however, the colostomy may be permanent.
- Radiofrequency ablation: The use of a special probe with tiny electrodes
that kill cancer cells. Sometimes the probe is inserted directly through
the skin and only local anesthesia is needed. In other cases, the probe
is inserted through an incision in the abdomen. This is done in the hospital
with general anesthesia.
- Cryosurgery: A treatment that uses an instrument to freeze and destroy
abnormal tissue, such as carcinoma in situ. This type of treatment is also
called cryotherapy.
Even if the doctor removes all the cancer that
can be seen at the time of the operation, some patients may be given chemotherapy
or radiation therapy after surgery to kill any cancer cells that are left.
Treatment given after the surgery, to increase the chances of a cure, is called
adjuvant therapy.
Chemotherapy
Chemotherapy is a cancer treatment that uses drugs
to stop the growth of cancer cells, either by killing the cells or by stopping
the cells from dividing. When chemotherapy is taken by mouth or injected into
a vein or muscle, the drugs enter the bloodstream and can reach cancer cells
throughout the body (systemic chemotherapy). When chemotherapy is placed directly
into the spinal column, an organ, or a body cavity such as the abdomen, the
drugs mainly affect cancer cells in those areas.
Chemoembolization of the hepatic artery may be
used to treat cancer that has spread to the liver. This involves blocking the
hepatic artery (the main artery that supplies blood to the liver) and injecting
anticancer drugs between the blockage and the liver. The liver’s arteries then
deliver the drugs throughout the liver. Only a small amount of the drug reaches
other parts of the body. The blockage may be temporary or permanent, depending
on what is used to block the artery. The liver continues to receive some blood
from the hepatic portal vein, which carries blood from the stomach and intestine.
The way the chemotherapy is given depends on the
type and stage of the cancer being treated.
Radiation therapy
Radiation therapy is a cancer treatment that uses
high-energy x-rays or other types of radiation to kill cancer cells. There
are two types of radiation therapy. External radiation therapy uses a machine
outside the body to send radiation toward the cancer. Internal radiation therapy
uses a radioactive substance sealed in needles, seeds, wires, or catheters
that are placed directly into or near the cancer. The way the radiation therapy
is given depends on the type and stage of the cancer being treated.
Other types of treatment are being tested in clinical trials. These include
the following:
Biologic therapy
Biologic therapy is a treatment that uses the
patient’s immune system to fight cancer. Substances made by the body or made
in a laboratory are used to boost, direct, or restore the body’s natural defenses
against cancer. This type of cancer treatment is also called biotherapy or
immunotherapy.
Follow-up exams may help find recurrent colon cancer earlier.
After treatment, a blood test to measure carcinoembryonic
antigen (CEA; a substance in the blood that may be increased when colon cancer
is present) may be done along with other tests to see if the cancer has come
back.
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Treatment of stage 0 (carcinoma in situ) may include
the following types of surgery:
- Local excision or simple polypectomy.
- Resection/anastomosis. This is done when the cancerous tissue is too large to
remove by local excision.
Treatment of stage I colon cancer is usually resection/anastomosis.
Treatment of stage II colon cancer may include
the following:
- Resection/anastomosis.
- Clinical trials of chemotherapy, radiation therapy, or biologic therapy after
surgery.
Treatment of stage III colon cancer may include
the following:
- Resection/anastomosis with chemotherapy.
- Clinical trials of chemotherapy, radiation therapy, and/or biologic therapy after
surgery.
Treatment of stage IV and recurrent colon cancer
may include the following:
- Resection/anastomosis (surgery to remove the cancer or bypass the tumor
and join the cut ends of the colon).
- Surgery to remove parts of other organs, such as the liver, lungs, and
ovaries, where the cancer may have recurred or spread.
- Radiation therapy or chemotherapy may be offered to some patients as palliative
therapy to relieve symptoms and improve quality of life.
- Clinical trials of chemotherapy and/or biologic therapy.
Treatment of locally recurrent colon cancer may
be local excision.
Special treatments of cancer that has spread to
or recurred in the liver may include the following:
- Radiofrequency ablation or cryosurgery.
- Clinical trials of hepatic chemoembolization with radiation therapy.
Patients whose colon cancer spreads or recurs
after initial treatment with chemotherapy may be offered further chemotherapy
with a different drug or combination of drugs.
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