Colon cancer is cancer of the large intestine (colon), the lower part of your digestive system. Rectal cancer is cancer of the last several inches of the colon. Together, they’re often referred to as colorectal cancers.
Most cases of colon cancer begin as small, noncancerous (benign) clumps of cells called adenomatous polyps. Over time some of these polyps become colon cancers.
Polyps may be small and produce few, if any, symptoms. For this reason, doctors recommend regular screening tests to help prevent colon cancer by identifying and removing polyps before they become colon cancer.
What Are the Symptoms of Colorectal Cancer?
In its early stage, colorectal cancer usually doesn’t have symptoms. That’s why it’s so important to keep up with the tests your doctor recommends to see if you have it, when it’s easiest to treat.
If you do have symptoms, the most likely ones include:
- Changes in bowel movements, including constipation or diarrhea that don’t seem to go away
- Feeling like you can’t empty your bowels completely or urgently need to have a bowel movement
- Bleeding or cramping in your rectum
- Dark patches of blood in or on your stool; or long, thin, “pencil stools”
- Discomfort or bloating in your belly
- Unexplained fatigue, loss of appetite, and weight loss
- Pelvic pain, which can happen in the later stages of the disease
When to Call Your Doctor
Lots of things can cause the symptoms listed above. So you’ll need to check with your doctor to find out what’s going on. Don’t just assume it’s hemorrhoids.
Make an appointment if you have any of the symptoms, or if a doctor tells you that you have anemia. (When doctors look for the cause of anemia, they should check for bleeding from the digestive tract because of colorectal cancer.)
Your doctor will most likely do a rectal exam. You may also get a sigmoidoscopy or a colonoscopy — exams that involve a long flexible tube put into your rectum so that your doctor can look for any cancers or growths that could become cancer.
Diagnosis of Colorectal Cancer
Doctors recommend certain screening tests for healthy people with no signs or symptoms in order to look for early signs of colon cancer. Finding colon cancer at its earliest stage provides the greatest chance for a cure. Screening has been shown to reduce your risk of dying of colon cancer.
People with an average risk of colon cancer can consider screening beginning at age 50. But people with an increased risk, such as those with a family history of colon cancer, should consider screening sooner. African-Americans and American Indians may consider beginning colon cancer screening at age 45.
Several screening options exist — each with its own benefits and drawbacks. Talk about your options with your doctor, and together you can decide which tests are appropriate for you.
If your signs and symptoms indicate that you could have colon cancer, your doctor may recommend one or more tests and procedures, including:
- Using a scope to examine the inside of your colon.Colonoscopy uses a long, flexible and slender tube attached to a video camera and monitor to view your entire colon and rectum. If any suspicious areas are found, your doctor can pass surgical tools through the tube to take tissue samples (biopsies) for analysis.
- Blood tests.No blood test can tell you if you have colon cancer. But your doctor may test your blood for clues about your overall health, such as kidney and liver function tests.
If a colon cancer diagnosis is made after a biopsy, doctors will often order chest x-rays, ultrasounds, or CT scans of the lungs, liver, and abdomen to see how far the cancer has spread. Your doctor may also test your blood for a chemical sometimes produced by colon cancers (carcinoembryonic antigen or CEA). Tracked over time, the level of CEA in your blood may help your doctor understand your prognosis and whether your cancer is responding to treatment.
Colorectal Cancer Prognosis
Colon cancer stages
After a diagnosis is made, your doctor will order tests to determine the extent (stage) of your cancer. Staging will help determine which choices will be available for treatment.
Staging tests may include imaging procedures such as abdominal and chest CT scans. In many cases, the stage of your cancer may not be determined until after colon cancer surgery.
The stages of colon cancer are:
- Stage I.Your cancer has grown through the superficial lining (mucosa) of the colon or rectum but hasn’t spread beyond the colon wall or rectum.
- Stage II.Your cancer has grown into or through the wall of the colon or rectum but hasn’t spread to nearby lymph nodes.
- Stage III.Your cancer has invaded nearby lymph nodes but isn’t affecting other parts of your body yet.
- Stage IV.Your cancer has spread to distant sites and other organs throughout the body.
Treatment of Colorectal Cancer
The type of treatment your doctor recommends will depend largely on the stage of your cancer. The three primary treatment options are surgery, chemotherapy and radiation.
Surgery to remove part of or the entire colon is called colectomy. During colectomy, a surgeon will remove the part of the colon containing the cancer as well as the marginal area close to the cancer.
Also, nearby lymph nodes are also usually removed. Depending on the extent of the colectomy, the healthy portion of the colon will either be reattached to the rectum or attached to an opening in the wall of the abdomen called a stoma. This latter option is called a colostomy, and waste will exit the body through the stoma into a colostomy bag, instead of exiting through the rectum.
In addition to invasive surgeries like colectomy, doctors can remove some small, localized cancers using endoscopy.
Laparoscopic surgery (using several small incisions in the abdomen) may also be an option to remove larger polyps.
Palliative surgery might also be employed to relieve symptoms for cancers that are advanced or untreatable. This type of surgery will try to relieve blockage of the colon or to inhibit other conditions to relieve pain, bleeding, and other symptoms.
Chemotherapy uses drugs to destroy cancer cells. Chemotherapy for colon cancer is usually given after surgery if the cancer has spread to the lymph nodes. In this way, chemotherapy may help reduce the risk of cancer recurrence. Chemotherapy may be used before surgery to shrink the cancer before an operation.
Chemotherapy can also be given to relieve symptoms of colon cancer that has spread to other areas of the body.
In people with rectal cancer, chemotherapy is typically used along with radiation therapy. This combination is often used before and after surgery.
Radiation therapy uses powerful energy sources, such as X-rays, to kill cancer cells that might remain after surgery, to shrink large tumors before an operation so that they can be removed more easily, or to relieve symptoms of colon cancer and rectal cancer.
Radiation therapy is rarely used in early-stage colon cancer, but is a routine part of treating rectal cancer, especially if the cancer has penetrated through the wall of the rectum or traveled to nearby lymph nodes.
Radiation therapy, usually combined with chemotherapy, may be used before surgery in order to make the operation easier and to reduce the chance that an ostomy will be necessary. It can also be used after surgery to reduce the risk that the cancer may recur in the area of the rectum where it began.
Side effects of radiation therapy may include mild skin changes resembling sunburn or suntan, nausea, vomiting, diarrhea, and fatigue. Patients also tend to lose their appetites and have trouble maintaining weight, but most side effects subside a few weeks after completing treatment.
Prevention of Colorectal Cancer
Colon cancer is the third most common cause of cancer death in the U.S., and it is the second most prevalent type of cancer.
The American Cancer Society recommends regular screening tests, particularly colonoscopy, for early detection of colon cancer. Colonoscopy is the best method, because it will visualize the entire colon and can remove polyps during the procedure. Other screening tests include fecal occult blood tests (annually), stool DNA testing, flexible sigmoidoscopy (every 5 years), and CT colonography (every 5 years).
These frequency recommendations depend, however, on a person’s particular risk of colon cancer due to other risk factors.
In general, physicians recommend standard preventive measures such as keeping a healthy weight, exercising, and increasing consumption of fruits, vegetables, and whole grains while decreasing saturated fat and red meat intake. In addition, people are recommended to limit alcohol consumption and quit smoking.
It is important for people to realize that with proper screening, colon cancer cannot only be detected early, but may also be prevented from developing.