If granted approval by the U.S. Food and Drug Administration, the novel test could emerge as a more appealing alternative to stool tests or colonoscopies.
In the United States, approximately one-third of adults aged 45 years and older are not undergoing the recommended screenings for colorectal cancer. Additionally, there has been a rise in colon cancer cases among younger individuals, although the underlying reasons remain unclear.
The U.S. Preventive Services Task Force advises that adults aged 45 to 75 should undergo colorectal cancer screening, while those aged 76 to 85 should engage in discussions with their healthcare provider to determine whether screening is appropriate.
Although colonoscopy stands as the gold standard for colorectal cancer screening, the requirement for vigorous laxatives prior to the procedure, coupled with the somewhat invasive nature of the examination under anesthesia, dissuades some individuals from seeking the necessary screening.
An alternative screening option known as Cologuard® (FIT-DNA) may be preferable for certain individuals. However, this method entails collecting a stool sample at home and sending it to a lab for analysis, which may deter some individuals.
Other screening options, including computed tomographic colonography (CTC) scans, flexible sigmoidoscopy, and stool tests such as the fecal immunochemical test (FIT) and high-sensitivity guaiac-based fecal occult blood test (gFOBT), exist. However, these alternatives may not be as effective in detecting colon cancer as FIT-DNA tests or colonoscopies.
Anticipation is high for the potential approval of the first blood test designed to screen for colorectal cancer this year, marking a significant advancement in combating the second-leading cause of cancer deaths in the United States.
While experts emphasize that this test won’t replace the gold standard of colonoscopy, it could revolutionize colorectal screenings by offering a less invasive and more acceptable method for detecting colon cancer.
Dr. William Grady, a gastroenterologist at Fred Hutchinson Cancer Center in Seattle, explained the importance of finding tests that people are willing to use, highlighting the potential of this blood test named Shield, developed by California-based Guardant Health. Grady’s research, published in the New England Journal of Medicine, demonstrates Shield’s overall effectiveness in detecting colorectal cancers at 83%.
Dr. Aasma Shaukat, a gastroenterologist at NYU Langone Health, expresses long-awaited enthusiasm for a blood-based test for colon cancer, recognizing its significance in overcoming barriers to screening.
Despite colonoscopy’s accuracy in detecting colorectal cancers and precancerous lesions, screening rates remain suboptimal, with less than 60% of eligible individuals up to date. Biachi and Shaukat, experts unaffiliated with the Guardant research, acknowledge the logistical challenges and discomfort associated with colonoscopies, which may deter individuals from undergoing screening.
Guardant’s blood test operates by identifying DNA released by cancerous tumors, primarily effective in detecting advanced-stage cancers. However, its efficacy in detecting early-stage polyps, crucial for timely intervention, is limited, raising concerns among clinicians.
While a positive Shield test would require follow-up with a colonoscopy for confirmation and precise tumor localization, the FDA’s potential approval of the test this year could significantly enhance screening accessibility, particularly for asymptomatic individuals aged 45 and above.
Despite the advancements, individuals exhibiting symptoms of colon cancer or with a family history of the disease would still necessitate a colonoscopy for comprehensive evaluation.