Colorectal Cancer Screening Tests
Colorectal cancer screening tests are used to detect cancer early or prevent it by identifying and removing precancerous polyps in the colon or rectum.
Overview
Colorectal cancer often begins as colorectal polyps—abnormal growths that are usually benign but can become cancerous over time. Screening allows providers to find and remove these polyps or detect cancer at an early, more treatable stage.
Screening Options
Visual Exams
- Colonoscopy: Examines the entire colon and rectum. Requires bowel prep and sedation. Polyps can be removed or biopsied during the procedure.
- Sigmoidoscopy: Examines the rectum and lower colon. Usually requires less prep than a colonoscopy and no sedation.
- Virtual Colonoscopy (CT colonography): Uses X-rays and a computer to create 3D images of the colon. Requires bowel prep but no sedation.
Stool Tests
- Fecal Immunochemical Test (FIT): Checks for hidden blood in the stool.
- Guaiac Smear Test (gFOBT): Uses a chemical reaction to detect hidden blood; requires specific dietary restrictions before testing.
- Stool DNA (FIT-DNA) Test: Checks for genetic changes in the stool that may indicate polyps or cancer.
Why do I need screening?
If you are at average risk, screening is generally recommended starting at age 45. You may need to start earlier or be screened more frequently if you have risk factors such as a family history of colorectal or ovarian cancer, inflammatory bowel disease (ulcerative colitis or Crohn's disease), obesity, smoking, or alcohol misuse.
What do the results mean?
Abnormal results on stool tests do not confirm cancer but indicate the need for a follow-up colonoscopy. If polyps are found during a visual exam, they are typically removed and sent to a lab for testing. If your results are abnormal, your provider will discuss the next steps for diagnosis and treatment.