News Health/Medical Can a Blood Test Detect Colorectal Cancer?
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Can a Blood Test Detect Colorectal Cancer?

By Pat Carragher - March 19, 2024

As the number of colorectal cancer cases rise, so does the need for new and better ways to detect the disease. A recent study reveals promising results: a blood-based screening test detected colorectal cancer in 83% of individuals with the disease. Let's delve into the details:

The Blood-Based Screening Test

The test, performed through a simple blood draw, examines the sample for circulating tumor DNA (ctDNA) left behind in the bloodstream. In a cohort at average risk for colorectal cancer, the cell-free DNA blood-based test demonstrated:

  • 83% sensitivity for colorectal cancer
  • 90% specificity for advanced neoplasia
  • 13% sensitivity for advanced precancerous lesions

Colonoscopy vs. Blood Test

While the blood test offers a less invasive option, it can only detect cancer once it has already developed. In contrast, during a colonoscopy, doctors can identify and remove polyps five to ten years before they potentially turn into cancer. Therefore, screening colonoscopy remains the gold standard for detecting and preventing colorectal disease.

Encouraging More Screenings

Dr. Tiago Biachi, a gastrointestinal oncologist at Moffitt Cancer Center, emphasizes the importance of screenings. Although the ideal scenario involves everyone getting a first colonoscopy at age 45, this isn't always feasible. However, if blood tests can encourage more people to seek colonoscopies, it's a positive step.

Who Should Get Screened?

The U.S. Preventive Services Task Force recommends colorectal cancer screenings starting at age 45 for those at average risk. This includes individuals with:

  • No prior diagnosis of colorectal cancer
  • No family history or genetic disorders increasing risk
  • No history of precancerous polyps
  • No diagnosis of inflammatory bowel disease

Final Thoughts

While the blood test provides valuable insights, it isn't an official diagnosis. Anyone testing positive would still need a colonoscopy for confirmation. Additionally, only a colonoscopy can precisely locate tumors within the colon, influencing treatment decisions.

The FDA is expected to consider approval of the blood test this year.

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