Can A Blood Test Detect Colon Cancer?

As per the researchers who reported at the 2025 American Society of Clinical Oncology Gastrointestinal Cancers Symposium which was held last week in San Francisco, an experimental blood test can accurately and effectively detect colon cancer. The researchers also emphasized on its detection in middle-aged and senior population. The blood test had an 81% accuracy rate in detection. It was also 90% accurate in ruling out colon cancer among healthy people.

Why Is It The Need Of The Hour?

Such a test is need of the hour because it helps people determine whether they require a screening. While as per the Cancer Screening Guidelines by Age by the American Cancer Society, it is generally recommended for people after 40 to consider colon cancer screening, the reality is far from it. Around 22% of people eligible for colon screening have never received it, in some states the percentage is higher than 40%.

The study is published by Aasma Shaukat of the NYU Grossman School of Medicine, titled Performance of a blood-based test for colorectal cancer screening adjusted to the US census age and sex distribution.

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What Tests One Should Get For Colon Cancer?

The standard test for colon cancer is colonoscopy. However for this, patients must often undergo unpleasant bowel preparation and then be anesthetized during the procedure. Fecal blood tests are also used to screen for colon cancer, annually.

A colonoscopy is a medical procedure that allows a doctor to examine the inside of the colon and rectum. A doctor in this process inserts a colonoscope with a long, flexible tube with a camera and light into the rectum and colon and the camera sends images to a monitor to provide magnified view of the colon lining.

How Can You Prepare For A Colonoscopy?

Usually, one needs to take a laxative to empty their bowels and also follow a special diet a day before the procedure. This would be communicated by your GP or the doctor you have an appointment with. People are recommended to also avoid red liquids, which may be mistaken for blood during the procedure. Before the procedure starts, inform your doctor for any medication you are prescribed, and or any existing health issues like diabetes, heart problem, or high blood pressure.

“Until now, we have only had stool-based tests and colonoscopy or sigmoidoscopy. A blood test has the potential for improving colorectal cancer screening rates,” Shaukat said.

ALSO READ: What Are Colorectal Cancers? Is It Different From Colon Cancer?

How Was The Study Conducted?

The researchers tried the experimental blood test on more than 40,000 people aged between 45 to 85 at 200 sites across the United States. These people had their blood drawn and then underwent a standard colonoscopy. Researchers then compared the results to see how well the blood tests stacked up against colonoscopy.

What Did The Study Find?

The blood-based screening test met all primary endpoints, with a sensitivity for colorectal cancer of 79.2% and a specificity for advanced colorectal neoplasia of 91.5%.

Shaukat also noted that this analysis provided a "snapshot of how the test would perform in the US population" and that the sensitivity for colorectal cancer and advanced precursor lesions was "lower than expected and will continue to be optimized in future research development."