Colorectal Cancer Screening – Kira Specialist

When a person is asymptomatic, screening methods are used to screen for different types of cancer.

Scientists are exploring screening methods that do the least harm and the most good. Cancer screening trials are also designed to confirm whether early detection (finding cancer before it produces symptoms) can extend a person’s life or reduce cancer mortality. For some types of cancer, the chances of recovery are higher if the cancer is detected and treated at an early stage.

Studies have shown that some colorectal cancer screening methods can help achieve early detection of cancer and may reduce the number of colorectal cancer deaths.

Five tests used to screen for colorectal cancer:

Fecal occult blood test

The fecal occult blood test (FOBT) is a test that examines stool (solid waste) through a microscope for the presence of blood. A small stool sample is placed on a special card or in a special container and given to a doctor or testing laboratory for testing. The presence of blood in the stool indicates the possible presence of polyps, cancer, or other diseases.

There are two types of fecal occult blood tests (FOBT):

Guaiac chemical fecal occult blood test: A stool sample is placed on a special card and tested using a chemical reagent. This special card will change color if there is blood in the stool. Guaiac fecal occult blood test (FOBT) kit; shows card, applicator, and return envelope.

Guaiac fecal occult blood test (FOBT) kit; shows card, applicator, and return envelope.

guaiac chemical fecal occult blood test (FOBT) checks for the presence of occult (hidden) blood in the stool. A small stool sample is placed on a special card and given to the doctor or testing laboratory for testing.

Immunochemical method of fecal occult blood testing: A liquid is added to the stool sample and the mixture is injected into a machine containing antibodies to detect blood in the stool. If there is blood in the stool, a line appears in the machine’s display.

Fecal immunochemical test (FIT); drawing shows a FIT kit, which includes the package insert, the collection paper, and a collection tube Also shown are the biohazard bag, the return envelope, and a paper with information about colorectal cancer and colorectal Also shown are the biohazard bag, the return envelope, and a paper with information about colorectal cancer and colorectal cancer screening.

The fecal immunochemical test (FIT) is a test for occult (hidden) blood in the stool. A small stool sample is placed on a special collection tube or special card and given to a doctor or testing laboratory for testing.

Sigmoidoscopy

Sigmoidoscopy is a test that is used to look for polyps, lesions, or cancer inside the rectum and sigmoid colon (lower section). A sigmoidoscope is a slender tube-like instrument with a light and lens for observation that is inserted through the rectum into the sigmoid colon for exploration. It can also be used to remove polyps or tissue samples that can be microscopically determined to be cancerous.

Sigmoidoscopy; shows sigmoidoscope inserted through the anus and rectum and into the sigmoid colon. Inset shows patient on table having a sigmoidoscopy.

Sigmoidoscopy. A fiberoptic endoscope is inserted through the anus and rectum into the lower part of the colon to view the abnormalities.

Colonoscopy

Colonoscopy is a test used to explore polyps, lesions, or cancer in the rectum and colon. A colonoscope is a slim tube-like instrument with a light and lens for observation that is inserted through the rectum to probe the colon. It can also be used to remove polyps or tissue samples for microscopic determination of the presence or absence of cancer.

Colonoscopy; shows colonoscope inserted through the anus and rectum and into the colon. Inset shows patient on table having a colonoscopy.

Colonoscopy. A fiberoptic endoscope is inserted through the anus and rectum into the lower part of the colon to examine the abnormality.

Virtual colonoscopy

Virtual colonoscopy is a test that uses x-rays (called computed tomography) to take a series of images of the colon. The computer reorganizes these images into specific images that show polyps and suspicious lesions inside the colon. This test is also known as computed tomography colonoscopy or CTC.

Virtual colonoscopy is currently being compared with other colorectal cancer screening methods through clinical trials. Some clinical trials are testing whether polyps can be clearly visualized by drinking a contrast agent that coats the stool rather than emptying the colon with a laxative.

Fecal DNA testing

This test is used to detect genetic changes in fecal cells, which may be a biomarker for colorectal cancer.

Studies have shown that screening for colorectal cancer by rectal screening has not reduced the number of colorectal cancer deaths.

A rectal finger examination (DRE) is a rectal exam that can be done as part of a routine physical exam. A doctor or nurse inserts a gloved, lubricated finger into the lower part of the rectum to check for lumps or other abnormalities. The results of the study suggest that DRE cannot be used as a screening method for colorectal cancer.

Screening methods for colorectal cancer are being studied in clinical trials

For information about NCI-supported clinical trials, check the NCI’s Clinical Trials Search page. Other organization-supported clinical trials can be found at ClinicalTrials.gov.