Screening > Up-and-Coming Screening Tests |
The following are new screening tests in development which may prove to be effective, patient-friendly options for detecting early signs of colorectal cancer and polyps in the future.
Stool DNA Test
A stool DNA test is an at-home test completed by the patient. Unlike other stool tests that check for blood, a stool DNA test examines cells in the stool for genetic mutations associated with colorectal cancer and polyps. Cells from the bowel are continually shed and passed in feces; this includes cells from cancers and polyps. The test requires an entire bowel movement for analysis. Once the patient has collected the bowel movement in a special container attached to a toilet, he/she ships the package to a laboratory for evaluation. Through a series of laboratory procedures, specific genes are identified, and if found to be altered, the patient is required to undergo a colonoscopy to examine the bowel for evidence of cancer or polyps and perform biopsy if needed.
Blood Test
Several types of blood tests are being evaluated for detecting signs of colorectal cancer and, in some cases, polyps. These tests differ in the markers they look for in the blood that are associated with colorectal cancer and polyps, i.e. genetic or chemical markers. Those who test positive for the markers must undergo a colonoscopy to determine if disease is present. The ColonSentry test is the world’s first commercially available blood test for colon cancer screening. It is currently only available in Ontario, Canada. More information available at: http://www.colonsentry.com
Rectal Mucous Test
In this test, a sample of mucous from the patient’s rectum is obtained by a doctor and smeared onto a test strip which is sent to a laboratory. The sample is processed to identify the amount of a carbohydrate present that is associated with colorectal cancer. Patients with a positive test must undergo a colonoscopy.
Saliva Test
This test involves a simple saliva sample taken from the patient’s mouth and sent to a laboratory where cellular DNA is analyzed for a genetic alteration associated with a predisposition to developing colorectal cancer. Unlike the other screening tests that help determine current risk of colorectal cancer, this test helps determine the chances of developing the disease during an individual’s whole lifetime. The results of the saliva test, along with environmental risk factors such as smoking and age, are entered into a software calculation to establish the patient’s lifetime risk. The final test results categorize the patient as either low, medium or high risk for lifetime development of colorectal cancer. He/she can then be monitored with appropriate screening tests and interval times.
Capsule Colonoscopy
A capsule colonoscopy requires the patient to ingest a disposable capsule, about the size of a large vitamin pill, containing a miniature video camera at each end that travels through the digestive tract. Special sensors are affixed to the patient’s abdomen and connected to a recording device worn on a belt around the waist. As the capsule travels through the digestive tract (which takes about 10 hours), it captures thousands of images and transmits them through the sensors to the recording device. After the 10 hours, the patient returns the recording device to the doctor who downloads the images onto a computer for review in a moving video format. The pill passes naturally from the patient’s body in a bowel movement and does not need to be retrieved. A conventional colonoscopy is required if abnormalities are seen on the video.
Fecal Immunochemical Tests for Colorectal Cancer Screening: A Systematic Review of Accuracy & Compliance
The fecal immunochemical test (FIT), also called an immunochemical fecal occult blood test (iFOBT), is a newer kind of test that also detects occult (hidden) blood in the stool. This test reacts to part of the human hemoglobin protein, which is found on red blood cells.
The FIT is done essentially the same way as the FOBT, but some people may find it easier to use because there are no drug or dietary restrictions (vitamins or foods do not affect the FIT) and sample collection may take less effort. This test is also less likely to react to bleeding from parts of the upper digestive tract, such as the stomach.
As with the FOBT, the FIT may not detect a tumor that is not bleeding, so multiple stool samples should be tested. And if the results are positive for hidden blood, a colonoscopy is required to investigate further. In order to be beneficial the test must be repeated every year.