Colorectal Cancer

If your doctor thinks you may have colorectal cancer, he or she will ask you questions about your medical history and give you a physical exam. Other tests may include:

• A colonoscopy, a test in which your doctor uses a lighted scope to view the inside of your entire colon. A colonoscopy may be done to look into symptoms such as unexplained bleeding from the rectum, constant diarrhea or constipation, blood in the stool, or pain in the lower abdomen. A colonoscopy is recommended when another screening test shows you may have colorectal cancer.⁶
• A digital rectal examination, in which your doctor puts a gloved finger into your rectum. This exam is done to look into symptoms such as rectal bleeding or blood in the stool, abdominal or pelvic pain, a change in bowel habits, or urinary problems in men.
• Fecal occult blood test (FOBT), or fecal immunochemical test (FIT), in which your stool is tested with a special solution to see if it contains blood. Or a stool DNA test (sDNA) may be used to check for signs of cancer.
• A sigmoidoscopy, a test in which your doctor uses a lighted scope to view the lower part of your intestine. A sigmoidoscopy may be done to look into symptoms such as unexplained bleeding from the rectum, constant diarrhea or constipation, blood in the stool, or pain in the lower abdomen. Doctors can also remove polyps during this test.
• A barium enema, in which a whitish liquid with barium is inserted through your rectum into your intestine. The barium outlines the inside of the colon so that it can be seen on an X-ray.
• Computed tomographic colonography (CTC), also known as virtual colonoscopy. This test uses X-rays and a computer to make a detailed picture of the colon to help the doctor look for polyps. It may be used as a screening test for people who do not have an increased risk for colon cancer or in people who cannot have a colonoscopy.
• A biopsy, in which a sample of tissue is taken from the inside of your intestine and examined under a microscope. A doctor called a pathologist can look at the tissue sample and see if it contains cancer.
• A complete blood count, which is a blood test. It is used to look into symptoms such as fatigue, weakness, anemia, bruising, or weight loss.

For people who have an increased risk for colorectal cancer, regular colonoscopy is the recommended screening test because it allows your doctor to remove polyps (polypectomy) and take tissue samples at the same time.

When you are diagnosed with colorectal cancer, your doctor may order other tests to determine whether the cancer has spread. These tests include:

• A CT scan to see if the cancer has spread to your liver, lungs, or abdomen.
• A chest X-ray to see if the cancer has spread to your lungs.
• An MRI or PET scan to see if the cancer has spread into your chest or organs in the abdomen or pelvis.
• An ultrasound to find the cause of abdominal pain or increased abdominal girth or to see if the cancer has spread to your liver.
• A blood chemistry panel to see if the cancer has spread to your liver and bones.
• A carcinoembryonic antigen (CEA) blood test to see if the cancer has returned after treatment.

Early Detection

Colorectal cancer is very treatable and can usually be cured when it is caught early. Most people who get colorectal cancer are older than 50 and have no other risk factors besides their age. See the What Increases Your Risk section of this topic for more information.

Research shows that routine screening greatly reduces deaths from colorectal cancer.⁶ Screening tests look for a certain disease or condition before any symptoms appear. Screening methods include:

• Stool tests, such as the fecal occult blood test (FOBT), the fecal immunochemical test (FIT), and the stool DNA test (sDNA).
• Sigmoidoscopy.
• Colonoscopy.
• Computed tomographic colonography (CTC), also known as virtual colonoscopy.

Talk to your doctor about which test is right for you. People with a higher risk for colorectal cancer, such as African Americans and people with a strong family history of colon cancer, may need to begin routine testing before age 50 and have it more often.

If you have a very strong family history of colon cancer, you may want to talk to your doctor or a genetic counselor about having a blood test to look for changed genes. Genetic testing can tell you whether you carry a changed, or mutated, gene that can cause colon cancer. Having certain genes greatly increases your risk of colon cancer. But most cases of colon cancer are not caused by changed genes.

Which test should I have to screen for colorectal cancer?