Screening and Diagnosis

Screening and Diagnosis of Colon and Rectal Cancer

The cause of most colon and rectal cancer is unknown. Certain risk factors could be contributing causes, including:

  • Age: Colon and rectal cancer can affect people at any age, although most are over 50.
  • Race and ethnicity: Black people have the highest risk for colorectal cancer of all racial groups in the United States. Jewish people of Eastern European descent, such as Ashkenazi Jewish people, have the highest colorectal cancer risk of any ethnic group in the world.
  • Diet: Colorectal cancer is associated with a diet high in red and processed meats.
  • Personal history of colorectal polyps: Benign growths on the wall of the colon or rectum are common in people aged 50 and older and may lead to colorectal cancer.
  • Personal history of colorectal cancer: People who have had colorectal cancer are at higher risk for having it again.
  • Family history: People with a strong family history of colorectal cancer or polyps in a first-degree relative (a parent or sibling before the age of 45 or two first-degree relatives of any age) are at a higher risk for colorectal cancer.
  • Ulcerative colitis or Crohn's disease: People who have an inflamed colon lining have a higher risk of colorectal cancer.
  • Inherited conditions: These include familial adenomatous polyposis (FAP) or hereditary nonpolyposis colon cancer (Lynch syndrome).
  • Weight: People with a body mass index (BMI) over 30 are at a higher risk of colorectal cancer.
  • Physical inactivity: Adults should get two-and-a-half hours weekly of aerobic activity, such as walking, to decrease risk of colorectal cancer.
  • Heavy alcohol consumption: Men who drink more than five drinks a day and women who drink more than four drinks a day have a higher risk of colorectal cancer.
  • Type 2 diabetes: Colorectal cancer and Type 2 diabetes share some of the same risk factors, such as weight and physical inactivity.
  • Smoking: Smokers have a higher risk of many cancers, including colon and rectal cancer.
  • Some genetic syndromes: A small percentage of colon and rectal cancers may be caused by inherited gene mutations. If you have a family history of colorectal cancer, talk to your physician about genetic testing. The American Cancer Society recommends that anyone receiving genetic tests consult a physician or geneticist who is qualified to explain the significance of these test results.

Talk to your physician about lowering your risk factors for colon and rectal cancer.

Screening for Colon and Rectal Cancer

Regular colonoscopy screenings are recommended for anyone aged 45 years and older. Colorectal cancer screening benefits people without symptoms or strong risk factors. Screening procedures include:

  • Colonoscopy: A physician views the entire length of the colon with a flexible, lighted tube.
  • Sigmoidoscopy: A physician views a part of the large intestine with a flexible, lighted tube.
  • Biopsy: A physician takes a small sample of tissue during a colonoscopy or sigmoidoscopy to examine under a microscope.
  • Digital rectal exam (DRE): A physician uses their hands to check for abnormalities of the colon and prostate.
  • Fecal occult blood test: This test looks for microscopic or invisible blood in the stool.
  • Barium enema: This X-ray procedure uses barium (a metallic, chemical, chalky liquid) to coat the inside of organs so that they will appear on X-ray images.
  • Lynch syndrome testing: may be recommended for patients with a family history of colorectal cancers.

Diagnosing Colon and Rectal Cancer

There are a variety of leading-edge tools available to diagnose colorectal cancer. Most commonly they include:

  • Blood tests: Blood tests look for anemia, which can result from a bleeding tumor.
  • Imaging tests: Procedures such as CT scan, PET scan, ultrasound or MRI of the abdomen may be done to look for tumors or other problems. These tests may also be done if you have been diagnosed with colon or rectal cancer to help determine the extent (stage) of the cancer.

Stages of Colon and Rectal Cancer

“Staging” is the term oncologists (physicians specially trained in cancer care) use to define where pancreatic cancer is located and how much it has spread. After the stage of colon cancer is determined, your physician can recommend a particular course of treatment.

Most cancer teams use the system developed by the American Joint Committee on Cancer, known as the TNM staging system.

T = Tumor
Where is the primary tumor and how large is it?

N = Nodes
Has the tumor spread to nearby lymph nodes (part of your immune system)?

M = Metastasis
Has cancer spread to other parts of the body?

For each letter, there are five numbered stages, from zero to four, depending on how much the cancer has spread. The lower the number, the more the cancer cells look like normal cells and the easier they are to treat and cure. A higher number means it has spread more.

The place where cancer forms is called the primary site. Cancer can spread from the primary site to other parts of the body. Even if colorectal cancer is found in other parts of your body, it’s still considered colorectal cancer. For example, if colorectal cancer has spread to the liver, it’s called metastatic colorectal cancer, not liver cancer.

For treatment, physicians often use a simpler system of categorizing colorectal cancer:

  • Resectable cancer: These cancers can be surgically removed (resected).
  • Borderline resectable cancer: These cancers can be surgically removed but are very close to major blood vessels or other important parts of your body.
  • Locally advanced cancer: These cancers are still only in the area around the pancreas, but they cannot be removed completely with surgery, often because they are growing into nearby blood vessels. This category is also called unresectable because the cancer cannot be removed with surgery.
  • Metastatic cancer: These cancers have spread to other parts of the body, so they cannot be removed completely with surgery (meaing they are also unresectable). Surgery may still be done, but it's used to relieve symptoms that the tumors in other areas of the body are causing.

Talk to your physician about your stage of cancer and how that will impact your treatment.

For more information about the stages of colorectal cancer, please visit our Health Library.