Regular screening can often find colorectal cancer early, when it is most likely to be curable. In many people, screening can also prevent colorectal cancer altogether. This is because some polyps, or growths, can be found and removed before they have the chance to turn into cancer.

Tests used to screen for colorectal cancer include:

• Guaiac-based fecal occult blood test (gFOBT) and fecal immunochemical test (FIT): Samples of stool (feces) are checked for blood, which might be a sign of a polyp or cancer.
• Stool DNA test: A sample of stool is checked for certain abnormal sections of DNA (genetic material) from cancer or polyp cells.
• Sigmoidoscopy: A flexible, lighted tube is put into the rectum and lower colon to check for polyps and cancer.
• Colonoscopy: A longer, flexible tube is used to look at the entire colon and rectum.
• Double contrast barium enema: This is an x-ray test of the colon and rectum.
• CT colonography (virtual colonoscopy): This is a type of CT scan of the colon and rectum.

gFOBT, FIT, and stool DNA testing mainly find cancer, but can find some polyps.

Sigmoidoscopy, colonoscopy, double contrast barium enema, and CT colonography are good at finding cancer and polyps. Polyps found before they become cancer can be removed, so these tests may prevent colorectal cancer. This is why these tests are preferred if they are available and you are willing to have them.