Health
New FDA-Approved Test Offers a Simpler Way to Screen for Colon Cancer
The fight against colorectal cancer (CRC), the second biggest cause of cancer deaths, has gained a significant advantage with the recent Food and Drug Administration (FDA) approval of a revolutionary blood test. California-based Guardant Health’s Shield is the first-ever blood test aimed at primary screening for CRC and is also deemed suitable for Medicare coverage.
This innovative procedure was given the green light following an extensive clinical trial involving 20,000 average-risk adults. The findings, which demonstrated an 83% sensitivity in detecting CRC, was made public in The New England Journal of Medicine in March.
Robert Smith, Ph.D. and senior vice president of Early Cancer Detection Science for the American Cancer Society in Atlanta confirmed that Shield is the lone blood test available for CRC screening. He emphasized the importance of this test, stating, “It compares favorably with other colorectal cancer screening tests,” such as colonoscopy, CT colonography, and stool tests. He also noted the test would likely have greater appeal for those never before screened or not recently screened.
The convenience of this test is another of its merits – it can be performed during a routine doctor’s visit, saving patients the hassle of prepping for procedures or missing work. “It offers the potential to detect colorectal cancer in a person who is non-adherent with screening recommendations, asymptomatic, and willing to get this test based on preference, convenience, or both,” clarifies Smith.
Dr. Shuji Ogino, chief of the Molecular Pathological Epidemiology program at Brigham and Women’s Hospital, echoes Smith’s support. He praises Shield’s “reasonable sensitivity and specificity compared to other blood/stool tests,” and affirms its simplicity and time efficiency when compared to a colonoscopy.
While the potential risks of using Shield on a regular basis have not been extensively studied, Smith suggests that the risks should be minimal. Conversely, he points out that Shield does not offer the same level of colorectal cancer prevention as a colonoscopy does, due to its inability to detect and remove precursor lesions (polyps). However, Smith is optimistic that the benefits of increased screenings will outweigh this drawback.
Stephen Grabelsky, M.D., a hematologist and medical oncologist at the Eugene M. & Christine E. Lynn Cancer Institute at Boca Raton Regional Hospital, also noted that the Shield blood test has a lower sensitivity rate when compared to the Cologard stool test for CRC detection. It is appropriate only for individuals with an average risk for colon cancer, excluding those with a family history of the disorder or a personal history of inflammatory bowel disease.
Currently, the compliance rate for colorectal cancer screenings is significantly low, about 59%, a figure far below the National Colorectal Cancer Roundtable’s target of 80% for eligible individuals. The introduction of the Shield blood test aims to increase the rate of compliance by offering a simpler and less invasive alternative.
The importance of early detection cannot be overstated, as colon cancer has a relative survival rate of 91% when detected early. This figure drops to a mere 14% if the cancer has metastasized to distant parts of the body. As stated by Michael Weist, a spokesperson from Guardant Health, “Early detection is critical. The most effective screening test is the test that gets done.”
The Shield test is expected to be made available commercially by this fall and is suggested for individuals aged 45 and above with an average risk for CRC. Smith advises people interested in the Shield test to discuss both its benefits and limitations with their healthcare provider before making a decision, and to also check if their insurance covers the test. He further notes, “It is important to appreciate that a colorectal cancer screening test that is positive is not complete until the patient has had a colonoscopy. Any non-colonoscopy screening test for colorectal cancer that is positive must be followed up with a colonoscopy.”
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