The most well-known and physician-recommended screening test for colon cancer is a colonoscopy. It is most often preferred over other screening tests because of the ability for the practicing physician to be able to detect and remove polyps during the procedure. However, the number of eligible adults who are not getting screened for cancer has prompted many physicians to offer options to their patients along with a colonoscopy. Stool-based kits are often prescribed to patients who are hesitant to get a colonoscopy and are at a low to average risk for colon cancer. These tests are done at home and do not require the complicated bowel cleansing or any form of sedation to screen for colon cancer. At home stool tests ask for a small sample of stool that is then analyzed in a lab for evidence of blood that may indicate the presence of a precancerous polyp or colon cancer.
Another new approach to colorectal cancer screening is the use of blood tests that detect the presence of cellular markers in the bloodstream. Polyps and tumors in the colon shed cells that are absorbed into the bloodstream. These cells are called circulating tumor cells (CTCs) and are made up of epithelial cells that are associated with colorectal tumors and adenomas.
Research scientists have developed a special blood test that uses antibodies to detect these cancerous cells. These blood tests have been shown to be highly sensitive and specific for detecting colorectal cancer, but unfortunately miss the detection of polyps.
Research scientists have developed a special test that uses antibodies to detect these cells. These blood tests have been shown to be highly sensitive and specific for detecting colorectal cancer, but unfortunately miss the detection of polyps. In this article, we will address the pros and cons of stool tests and blood tests to help increase your awareness of the benefits of each test in screening for colorectal cancer.
There are currently three stool tests that are approved for colorectal cancer screening in the United States. These include:
Fecal immunochemical test (FIT). This test uses antibodies that specifically react with a blood protein in the stool. Physicians typically order the test to be repeated annually.
Guaiac-based fecal occult blood test (gFOBT). Conducted yearly, the gFOBT uses a chemical (guiac) to detect microscopic amounts of blood in the stool.
Stool DNA test (also known as FIT-DNA test). The most current stool test combines the FIT test with a test that can detect abnormally mutated DNA in the stool. Unlike the FIT and gFOBT, a stool DNA test can be repeated every three years if no abnormalities are found.
People frequently prefer these tests over colonoscopies because the test is done in the comfort of your own home and is noninvasive and requires no bowel preparation.
Colorectal cancer cells are detected with blood tests using genetic or tumor biomarkers. If these biomarkers are detected in a blood test, then it only suggests that a person may have colon cancer.
Colorectal cancer cells are detected with blood tests using genetic or tumor biomarkers. If these biomarkers are detected in a blood test, then it only suggests that a person may have colon cancer.
These tests, like stool-based tests, do not diagnose colorectal cancer. Rather, both stool-based and blood tests detect signs of colon cancer in the form of hidden blood or tumor markers respectively. There are two main types of colorectal cancer blood tests, these include:
Tumor marker tests. Unlike FDA-approved screening stool tests such as FIT, FOBT, or Cologuardâ„¢, tumor marker blood tests that detect colon cancer tumor markers are typically used to monitor patients who already have been diagnosed with colorectal cancer. The most common tumor biomarkers for colorectal cancer is called carcinoembryonic antigen (CEA) and CA 19-9. These tests help to determine if cancer treatment is working and sometimes to determine how likely it is that the disease will recur.
DNA-based blood test. These tests detect mutated cells shed by colon cancer tumors that are found in the blood. They typically are looking for a specific biomarker (such as Septin 9) that is distinct from normal cells and is shed by colorectal cancer tumors.
$170
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References
American Cancer Society. Tests to diagnose and stage colorectal cancer. Retrieved from American Cancer Society: https://www.cancer.org/cancer/colon-rectal-cancer/detection-diagnosis-staging/how-diagnosed.html
Lin, K. W. (2019, July 01). mSEPT9 blood test (Epi proColon) for colorectal cancer screening. American Family Physician, 100(1), 10-11. Retrieved from AAFP: https://www.aafp.org/afp/2019/0701/p10.html
Sonora Quest Laboratories. (2021). Colorectal cancer screening blood test: BeScreened-CRC. Retrieved from Sonora Quest: https://www.sonoraquest.com/my-lab-request/colorectal-cancer-screening-blood-test-bescreened-crc/
Tsai, W.-S., et., al. (2019, October). Novel circulating tumor cell assay for detection of colorectal adenomas and cancer. Clinical and Translational Gastroenterology, 10(10). Retrieved from PMC: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6884354/