Colorectal Cancer Tests

Current guidelines recommend that people over the age of 45 with no symptoms should undergo colon cancer screening. Individuals with symptoms or additional risk factors should potentially start checking before that age. City of Hope specialists will recommend screening based on individualized risk factors specific to each person.

Colorectal cancer has traditionally been seen as a disease of older adults, but it is increasingly recognized that younger patients — especially young African American males — can also be affected by the disease.

For those with symptoms, diagnosis by a doctor — related to screening but distinct in important ways — is necessary to find out whether colorectal cancer is present. Symptoms include blood in the stool, change in bowel habits, abdominal pain and difficulty in passing stool.

Screening for Colorectal Cancer

Screening involves looking for cancer before you have symptoms. Polyps containing cancer cells can stay lodged in the colon wall for months or years without causing bleeding, pain or any other symptoms. Screening increases the chances of catching colorectal cancer at an early stage, before it has spread and when it is more likely to be cured.

At City of Hope, we are dedicated to increasing the number of lifesaving screenings for colorectal cancer. To support that effort, we offer state-of-the-art diagnostic tools, including:

  • Colonoscopy: This test uses a long, flexible tube with a tiny light and video camera on one end to examine your colon and rectum.
  • Stool DNA testing: This test, marketed as Cologuard, examines stool to look for certain gene changes that are associated with colorectal cancer.
  • Genetic screening: Our trained genetic counselors can review your personal and family history, help you determine cancer risk and provide recommendations to reduce cancer risk and detect cancer earlier. Genetic screening also helps our treatment teams make the most accurate diagnosis and develop a clearly defined treatment path.

Screening Saves Lives

Colorectal cancer is one of the most curable cancers, yet research shows tens of millions of people are skipping out on potentially lifesaving screening. The biggest reason is fear: 

  • Fear of bowel preparation 
  • Fear of the test 
  • Fear of the results 

But most of those concerns are unfounded. The gold standard for colorectal cancer screening — colonoscopy — is a painless exam that happens while a patient is sedated (sleeping), and is usually over in less than 30 minutes. 

The research is clear that colorectal cancer screening saves lives. 

Who Should be Screened?

The American Cancer Society recommends colonoscopies for everyone over age 45. You should start routine colorectal cancer screening at age 45 if you: 

  • Have no symptoms 
  • Have no personal or family history of benign or precancerous polyps
  • Have no personal or family history of colorectal cancer

Your screening should begin before age 45, and have more frequent followups if you: 

  • Have developed polyps or colorectal cancer in the past
  • Have a history of inflammatory bowel diseases such as Crohn’s disease or ulcerative colitis
  • Have first-degree relatives (parents, siblings) who developed colorectal cancer before age 45
  • Have a family history of inherited conditions associated with colorectal cancer, such as Lynch syndrome or familial adenomatous polyposis

For those 76 through 85 years of age, regular screening may no longer be necessary. The decision about whether to undergo tests should at that point be made in consultation with your doctor, weighing such considerations as your current health, your health history and your own personal preferences. 

Regular screening for colorectal cancer is no longer recommended for those 86 and older.

Diagnostic Tests and Tools for Colorectal Cancer 

At City of Hope, we use a number of tests and tools to detect colorectal cancer or conditions that can lead to it, in people who show potential symptoms. 

  • Colonoscopy: This procedure, also deployed for screening, uses a scope and video that lets your doctor examine the lining of your colon and rectum. Colonoscopy can detect precancerous growths on the lining of the colon or rectum, called polyps, as well as early cancers and conditions, such as inflammation. Removing polyps, which generally can be performed during colonoscopy, can prevent colorectal cancer. Colonoscopy is an outpatient test usually performed at the hospital or a surgery center. Your doctor receives special training to perform this test. 
  • Flexible sigmoidoscopy: This test is similar to colonoscopy, but may not require sedation. It involves using a thin, lighted tube with a small video camera on the end to examine your rectum and the lower part of your colon. It looks for polyps or other abnormal areas, which can be removed and sent to a lab for testing. 

Imaging tests can be useful for diagnosing colon cancer, determining how far cancer has spread, and whether the cancer is responding to treatment: 

  • CT scan: Computed tomography (CT or CAT) scans use X-rays to make detailed images of cross-sections of the body. They are useful in determining whether colorectal cancer has spread to other organs. 
  • Virtual colonoscopy (CT colonography): This test is a special type of CT scan that creates a 3D picture of the colon and rectum. Occasionally, doctors may employ CT colonography to follow up on a colonoscopy with unclear results. As with the standard colonoscopy, a patient’s colon must be inflated for the required visibility, but otherwise, the virtual colonoscopy is less invasive and does not require an anesthetic. A patient could expect discomfort, such as bloating and cramping in the hour afterward. The main drawback of the CT colonography is that the doctor is unable to take samples or remove polyps. 
  • Double-contrast barium enema: A chalky white liquid called barium is put into the rectum, making it easier to see abnormal areas on an X-ray. 
  • Endoscopic ultrasound: This test uses sound waves to create an image of the inside of the body. In this procedure, an instrument is inserted into the rectum. It is useful for determining how far colorectal cancer has spread. 
  • MRI: MRI uses radio waves to create detailed images of the body’s soft tissues. It is useful for determining how far colorectal cancer has spread. 
  • PET scan: This procedure uses a form of radioactive sugar to detect cancer cells, which take up sugar more quickly than healthy cells. This test can be helpful for determining whether abnormal areas seen on other tests are cancerous or not. 

Other tests can help doctors diagnose cancer, determine how far it has spread and suggest the best treatments: 

  • Blood tests: Blood tests can show if you have anemia (low red blood cells), which can be associated with colorectal cancer. Blood tests can also detect tumor markers or substances made by colorectal cancer cells that can be present in the blood. Such tumor markers include carcinoembryonic antigen (CEA) and CA 19-9. 
  • A fecal occult blood test or fecal immunochemical test: These are tests you can do at home to detect blood in the stool. If the tests find blood in the stool, your doctor will recommend further tests, such as a colonoscopy. 
  • Stool DNA test: This test, also used for screening, looks for DNA changes in cells in the stool that might be signs of cancer. A type of fecal occult blood test, Cologuard, is currently the only Food and Drug Administration-approved stool DNA test. The least invasive method for early detection, Cologuard requires a patient to collect a stool sample at home with a kit and send it to a laboratory. If the results detect evidence of cancer or precancerous adenomas, a patient typically undergoes a colonoscopy. 
  • Gene tests: When doctors find cancerous cells in the colon or rectum, they may test them for certain gene changes that can help determine how best to treat cancer. 

A colonoscopy is the only test that lets the provider see your entire colon and rectum, and can remove polyps and tissue samples at the same time. If you have any of the other tests and something uncertain is found, you will likely need a colonoscopy.