Colon Cancer Screening Guidelines

A variety of tests are available to screen for colon cancer, and the decision as to which test to use depends upon the patient's risk factors, age and what tests they are willing to undergo.

Colon and rectal cancers are relatively common in both men and women. These cancers arise from the inner lining of the colon and rectum, and initially do not have any symptoms. Only after the cancer has grown in size or has spread beyond the colon, do symptoms present. These symptoms include blood in the stool, change in stool consistency, abdominal pain and bloating, fatigue, and weight loss. Because these symptoms are often late signs of the cancer, screening for colon cancers is an important part of decreasing mortality.

Screening for colorectal cancer allows the diagnosis to be made in otherwise healthy-appearing people who have yet to develop symptoms. In patients with polyps (pre-malignant or benign lesions), their removal can prevent cancers from forming. In those who have small cancers, their early detection and treatment can lead to higher survival and lower death rates.

The risk of colon cancer increases with age, especially for those older than 60. Other risk factors include:

• Diabetes
• Smoking
• Alcohol use
• Obesity
• Patients with inflammatory bowel disease (Crohn’s disease, ulcerative colitis) are at higher risk.

Patients who have had a previous colon polyp or colon cancer are at higher risk for recurrence.

Those who have had a first degree relative (parent, sibling, child) with polyps or colon cancer may be at higher risk, depending upon the number and type of polyp. This is one of the reasons why it is important to share medical information with family members and your doctor.

Some colorectal cancers are inherited. These are relatively rare, with 10-20 cases diagnosed in total per one million people. They include the following:

• Hereditary non-polyposis colorectal cancers
  • Lynch syndrome
  • Sporadic colorectal carcinomas
  • Turcot syndrome, type I
  • Muir-Torre syndrome
• Hereditary polyposis colorectal cancers
  • Familial adenomatous polyposis
  • Adenomatous polyposis syndromes 
  • Peutz-Jeghers syndrome
  • Turcot syndrome type II
  • Gardner syndrome
  • Cowden syndrome

Patients who do not have any of these risk factors are considered to be at average risk for developing colorectal cancer.

What does a colon screening consist of?

A variety of tests are available to screen for colorectal cancer, and the decision as to which test to use depends upon the patient’s risk factors , age and what tests they are willing to undergo. Testing recommendations should involve a discussion between the health care provider and the patient, and individualized for each patient.

Colonoscopy visualizes the whole lining of the colon using a camera attached to a flexible scope. If a polyp is found, it can be removed immediately. Similarly, if there is an abnormal mass, it can be biopsied during the colonoscopy. Colonoscopy is the recommended procedure to screen for colon and rectal cancers.

Sigmoidoscopy using a camera and flexible scope can only visualize the rectum, sigmoid colon, and descending colon, and not the transverse or ascending colon

Computed tomography (CT) colography is also called virtual colonoscopy, and uses CT scans to take images of the colon looking for abnormalities.

Fecal immunochemical testing (FIT) measures hemoglobin (a blood component) in a stool sample.

FIT-DNA (multitarget fecal DNA) is a test known as Cologuard in the United States, which screens a stool sample for DNA that may be shed by cancer cells.

In patients with average risk:

Screening begins at age 45

• Colonoscopy every 10 years (preferred), or
• CT colongraphy every 5 years, or
• Flexible sigmoidoscopy every 5 years, or
• Flexible sigmoidoscopy every 10 years + FIT every year, or
• FIT for occult blood every year, or
• multitarget fecal DNA (Cologuard) every 1-3 years

In patients with enhanced risk:

Screening begins at age 40

• Colonoscopy every 5 years (preferred), or
• FIT annually, or
• multitarget fecal DNA (Cologuard) annually

Screening should stop at age 85. For patients age 76- 85, the decision to continue screening should be based on their previous screening results, their risk for developing colorectal cancer, their personal preference, and their life expectancy.