Colon cancer
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).
Anatomy of the lower digestive system, showing the colon and other organs.
Age and health history can affect the risk of developing colon cancer.
Anything that increases your chance of getting a disease is called a risk factor. Having a risk factor does not mean
that you will get cancer; not having risk factors doesn’t mean that you will not get cancer. People who think they may
be at risk should discuss this with their doctor. 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 (small pieces of bulging tissue) in the colon.
Polyps in the colon. Some polyps have a stalk and others do not.
- A history of ulcerative colitis (ulcers in the lining of the large intestine) or Crohn disease.
- Certain hereditary conditions, such as familial adenomatous polyposis and hereditary nonpolyposis colon
cancer (HNPCC; Lynch Syndrome).
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. Other conditions may cause the same symptoms. 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.
- Frequent gas pains, bloating, fullness, or cramps.
- Weight loss for no known reason.
- Feeling very tired.
- 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.
Fecal Occult Blood Test (FOBT) kit to check for blood in stool.
- 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 anything else that seems unusual.
- Barium enema: A series of x-rays of the lower gastrointestinal tract. A liquid that contains barium (a silverwhite
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.
Barium enema procedure. The patient lies on an x-ray table.
Barium liquid is put into the rectum and flows through the
colon. X-rays are taken to look for abnormal areas.
- Sigmoidoscopy: A procedure to look inside the rectum and sigmoid (lower) colon for polyps (small pieces of
bulging tissue), abnormal areas, or cancer. A sigmoidoscope is inserted through the rectum into the sigmoid
colon. A sigmoidoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool
to remove polyps or tissue samples, which are checked under a microscope for signs of cancer.
- Colonoscopy: A procedure to look inside the rectum and colon for polyps, abnormal areas, or cancer. A
colonoscope is inserted through the rectum into the colon. A colonoscope is a thin, tube-like instrument with a
light and a lens for viewing. It may also have a tool to remove polyps or tissue samples, which are checked
under a microscope for signs of cancer.
- Biopsy: The removal of cells or tissues so they can be viewed under a microscope by a pathologist 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.
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 (CBC): 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 blood 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 colon. A substance called gadolinium is injected into the patient
through a vein. The gadolinium collects around the cancer cells so they show up brighter in the picture. 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.
There are three ways that cancer spreads in the body.
The three ways that cancer spreads in the body are:
- Through tissue. Cancer invades the surrounding normal tissue.
- Through the lymph system. Cancer invades the lymph system and travels through the lymph vessels to
other places in the body.
- Through the blood. Cancer invades the veins and capillaries and travels through the blood to other places in
the body.
When cancer cells break away from the primary (original) tumor and travel through the lymph or blood to other places
in the body, another (secondary) tumor may form. This process is called metastasis. The secondary (metastatic)
tumor is the same type of cancer as the primary tumor. For example, if breast cancer spreads to the bones, the
cancer cells in the bones are actually breast cancer cells. The disease is metastatic breast cancer, not bone cancer.
The following stages are used for colon cancer:
As colon cancer progresses from Stage 0 to Stage IV, the cancer
cells grow through the layers of the colon wall and spread to
lymph nodes and other organs.
Stage 0 (Carcinoma in Situ)
In stage 0, abnormal cells are found in the innermost lining of the colon. These abnormal cells may become cancer
and spread into nearby normal tissue. Stage 0 is also called carcinoma in situ.
Stage I
In stage I, cancer has formed and 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.
Recurrent Colon Cancer
Recurrent colon cancer is cancer that has recurred (come back) after it has been treated. The cancer may come back
in the colon or in other parts of the body, such as the liver, lungs, or both.
There are different types of treatment for patients with colon cancer.
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. 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. Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients
who have not started treatment.
Three types of standard treatment are used:
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.
Colon cancer surgery with anastomosis. Part of the colon containing the cancer and nearby
healthy tissue is removed, and then the cut ends of the colon are joined.
- 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. A
bag is placed around the stoma to collect the waste. 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.
Colon cancer surgery with colostomy. Part of the colon containing the cancer
and nearby healthy tissue is removed, a stoma is created, and a colostomy
bag is attached to the stoma.
- 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 them 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 (regional chemotherapy).
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 or
keep them from growing. 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.
New types of treatment are being tested in clinical trials.
This summary section describes treatments that are being studied in clinical trials. It may not mention every new
treatment being studied.
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.
Patients may want to think about taking part in a clinical trial.
For some patients, taking part in a clinical trial may be the best treatment choice. Clinical trials are part of the cancer
research process. Clinical trials are done to find out if new cancer treatments are safe and effective or better than the
standard treatment.
Many of today's standard treatments for cancer are based on earlier clinical trials. Patients who take part in a clinical
trial may receive the standard treatment or be among the first to receive a new treatment.
Patients who take part in clinical trials also help improve the way cancer will be treated in the future. Even when
clinical trials do not lead to effective new treatments, they often answer important questions and help move research
forward.
Patients can enter clinical trials before, during, or after starting their cancer treatment.
Some clinical trials only include patients who have not yet received treatment. Other trials test treatments for patients
whose cancer has not gotten better. There are also clinical trials that test new ways to stop cancer from recurring
(coming back) or reduce the side effects of cancer treatment.
Clinical trials are taking place in many parts of the country.
Follow-up tests may be needed.
Some of the tests that were done to diagnose the cancer or to find out the stage of the cancer may be repeated.
Some tests will be repeated in order to see how well the treatment is working. Decisions about whether to continue,
change, or stop treatment may be based on the results of these tests. This is sometimes called re-staging.
Some of the tests will continue to be done from time to time after treatment has ended. The results of these tests can
show if your condition has changed or if the cancer has recurred (come back). These tests are sometimes called
follow-up tests or check-ups.
For colon cancer, 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.
Treatment Options for Colon Cancer
Stage 0 (Carcinoma in Situ)
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 tumor is too large to remove by local excision.
Stage I Colon Cancer
Treatment of stage I colon cancer is usually resection /anastomosis.
Stage II Colon Cancer
Treatment of stage II colon cancer may include the following:
- Resection /anastomosis.
- Clinical trials of chemotherapy, radiation therapy, or biologic therapy after surgery.
Stage III Colon Cancer
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.
Stage IV and Recurrent Colon Cancer
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:
- Chemotherapy followed by resection.
- 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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