Colon and Rectal Cancer Detection & Diagnosis

As with most other cancers, colorectal cancer doesn’t always come with obvious signs and symptoms. Colorectal cancer is often found after symptoms appear. Still, most people with early colon or rectal cancer don’t have symptoms of the disease. Symptoms usually only occur with more advanced diseases. Therefore, it’s important to understand your family history and talk with your primary care physician about scheduling regular colorectal cancer screening.

Even if you’re feeling fine, the cancer specialists at Willamette Valley Cancer Institute encourage you to follow the recommended guidelines set in place by the American Society of Clinical Oncology, which is to be screened starting at age 50.

Find out more on risk factors of colon and rectal cancers

Screening for Colon and Rectal Cancers

Fortunately, several screening tests for colon and rectal cancers exist, including some recently made widely available. In addition to detecting colorectal cancer when it is present, regular screening can also prevent it by allowing your doctor to find and remove polyps before they have a chance to turn into cancer. If you’re 50 or older or have colorectal cancer in your family, we recommend talking to your doctor about colorectal cancer screening.

There are several common types of screening options. These tests range from those performed at a healthcare facility to some that can be done at home. Keep in mind that even though at-home testing offers more privacy, they are more prone to producing a false positive or a misinterpretation of the results.

Types of Colon and Rectal Cancer Screening Methods

Common colorectal cancer screening tests include:

  • Standard (or optical) colonoscopy: In this test, the rectum and entire colon are examined using a colonoscope, a flexible, lighted tube with a lens for viewing, and a tool for removing tissue. The patient is sedated during a colonoscopy procedure.
  • Virtual (CT) colonoscopy: This screening method, also called computed tomographic (CT) colonography, uses special x-ray equipment (a CT scanner) to produce a series of pictures of the colon and the rectum from outside the body.
  • Sigmoidoscopy: In this test, the rectum and lower (sigmoid) colon are examined using a sigmoidoscope, a flexible, lighted tube with a lens for viewing, and a tool for removing tissue. The doctor cannot check the upper part of the colon, the ascending and transverse colon, with this test.
  • Double-contrast barium enema (DCBE): An enema can be given containing barium. Once the barium has moved into the colon, x-rays are taken. The images are used to detect areas where there may be cancer. It’s not a good option for identifying precancerous polyps but is better than nothing if a colonoscopy or other physical exam isn’t possible.
  • Fecal Occult (Hidden) Blood Tests (FOBT): Two types of tests can be done at home to test for tiny amounts of blood in the stool: FIT and gFOBT. Blood in your stool can result from a polyp or cancerous tumor that has been irritated but does not cause enough bleeding to be seen during a bowel movement. One problem with FOBTs is that the doctor can’t tell if the blood detected is from within the colon or rectum. If there is blood found, a colonoscopy is usually the next step to see if the blood source is from within the colon.
    • Fecal Immunochemical Test (FIT): This test looks for hidden blood in the stool by reacting to the human hemoglobin protein part, which is found in red blood cells.
    • Guaiac-based fecal occult blood test (gFOBT): This is similar to the FIT, but with a different type of chemical reaction used to detect blood in the stool.
  • Stool DNA test: A test that detects tiny amounts of blood in the stool (with an immunochemical test similar to FIT) as well as nine DNA biomarkers in three genes that have been found in colorectal cancer and precancerous advanced adenomas. This test can be conducted at home.

The best screening method depends on factors such as your age and risk for developing colon and rectal cancer.

Screening Recommendations for Colorectal Cancer

Screening recommendations for colon and rectal cancer are different for each person based on whether they are at average risk or at high risk for the disease. It's important to learn your family history of cancer, know your risk, and get regularly screened at the appropriate age to detect colorectal cancer at an early stage.  

The American Society of Clinical Oncology (ASCO) has developed guidelines for patients who are at moderate risk. These patients would tend to have no family history of colorectal cancer and are, on average, fairly healthy. Beginning at age 50, both men and women should start screening.

Every year starting at age 50, perform a Fecal Occult Blood Test (FOBT) at home to detect signs of blood in the colon. This would be either the FIT or the Guaiac-based FOBT. A DNA Stool test would only be performed when directed by your physician. You may not need to have an actual colonoscopy or another internal exam every year. Discuss options with your doctor for other screening options in between.

Here is a recommendation based on physical exams in addition to annual FOBTs:

  • Flexible sigmoidoscopy, every five years or every ten years with FIT or FOBT every year
  • Colonoscopy, every ten years
  • Double-contrast barium enema (DCBE), every five years
  • Virtual colonoscopy, as often as your doctor recommends

If you are considered at high risk for colorectal cancer, your doctor may recommend earlier and more frequent screening. Factors that could indicate an increased risk of colorectal cancer include:

  • A family history of colon or rectal cancer
  • Problems with inflammatory disease, such as irritable bowel syndrome (IBS)
  • Radiation to the pelvic area from a previous cancer

Talk with your doctor if you feel as though you may fall into the high-risk category. Prevention is key and especially important for those at high risk of developing colon or rectal cancer.

Diagnosing Colon and Rectal Cancer

Suppose you have screening test results that suggest colorectal cancer or you have symptoms. In that case, your doctor must find out whether they are due to cancer or some other cause. Your doctor asks about your personal and family medical history and gives you a physical exam.

If your physical exam and test results do not suggest cancer, your doctor may decide that no further tests are needed, and no treatment is necessary. However, your doctor may recommend a schedule for checkups.

If tests show an abnormal area (such as a polyp), a biopsy to check for cancer cells may be necessary. Often, abnormal tissue can be removed during colonoscopy or sigmoidoscopy. A pathologist checks the tissue for cancer cells using a microscope.

When Test Results Come Back Abnormal

Further testing is often required before your doctor can diagnose colon or rectal cancer. When any test other than a colonoscopy indicates abnormalities, your doctor will typically order a colonoscopy to view the colon in its entirety. They can identify abnormal areas along the entire length of the colon and rectum with a colonoscope.

Additional tests that may be used to help diagnose colorectal cancer :
  • Blood tests: Your doctor checks for carcinoembryonic antigen (CEA) and other substances in the blood. Some people who have colorectal cancer or other conditions have a high CEA level.
  • Endorectal ultrasound: An ultrasound probe is inserted into your rectum. The probe sends out sound waves that people cannot hear. The waves bounce off your rectum and nearby tissues, and a computer uses the echoes to create a picture. The picture may show how deep a rectal tumor has grown or whether cancer has spread to lymph nodes or other nearby tissues.
  • PET-CT scan: A PET scan uses small amounts of radioactive materials, a special camera, and a computer to create pictures of organs and tissues inside the body. When a PET scan is combined with a CT scan, it is usually called a PET-CT scan.
  • Chest X-ray: X-rays of your chest may show whether cancer has spread to your lungs.
  • CT scan: An X-ray machine linked to a computer takes a series of detailed pictures of areas inside your body. You may receive an injection of dye. A CT scan may show whether cancer has spread to the liver, lungs, or other organs.
  • MRI: The use of magnetic fields, not x-rays, to produce detailed images of the body. You may receive an injection of dye, called a contrast medium, to create a clearer picture. MRI is the best imaging test to find where the colorectal cancer has grown.

Any polyps biopsied during a colonoscopy will be sent for testing. If they return a cancer diagnosis, your cancer doctor will work to stage the cancer. Discovering whether the cancer has spread helps the care team to determine the stage. Sometimes staging is not complete until after surgery to remove the tumor.

You can read more about staging on our Colon & Rectal Cancer Staging page.

It is important to remember that not all polyps are cancerous. It is always best to wait to hear the final results from your doctor before jumping to conclusions.

WVCI Cancer Specialists Are Here to Help

It is important to stay on top of your colorectal screening with your primary care physician. At Willamette Valley Cancer Institute, our highly experienced cancer care specialists are here to help treat your colorectal cancer with an individualized treatment plan.

In addition to paying attention to symptoms, and understanding more about your genetic risks, talking to your doctor about getting screened for colorectal cancer is arguably the most effective way you can reduce your risk.

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