A groundbreaking blood test for colorectal cancer detection might receive approval this year, potentially transforming the diagnostic process for the second-leading cause of cancer deaths in the United States.
This new test is not meant to replace colonoscopies, the current gold standard, but aims to increase colorectal cancer screening rates by providing a less intrusive option. According to Dr. William Grady, a gastroenterologist at Fred Hutchinson Cancer Center, existing tests like colonoscopies and stool-based screenings are often avoided due to their unpleasant nature, highlighting the need for more acceptable testing methods.
Recent research led by Grady, published in the New England Journal of Medicine, indicates that the Shield blood test by Guardant Health in California has an 83% effectiveness rate in detecting colorectal cancers, a significant development noted by experts in the field.
Dr. Aasma Shaukat of NYU Langone Health expressed excitement over the long-awaited blood-based test, citing its potential impact on colorectal cancer screening.
Challenges in Current Colorectal Cancer Screening
Colonoscopy remains the most precise method for early cancer detection, including pre-cancerous conditions, but under 60% of those eligible keep up with recommended screenings starting at age 45. Dr. Tiago Biachi from Moffitt Cancer Center points out the impracticality of expecting universal compliance with current colonoscopy guidelines.
Logistical hurdles, such as the requirement for patients to take strong laxatives prior to a colonoscopy and the need for a day off work and post-procedure transportation due to anesthesia, contribute to the low screening rates.
Grady emphasizes that the blood test circumvents these issues. It functions by identifying DNA from cancerous tumors, particularly effective in detecting later-stage cancers. However, a positive result would still necessitate a follow-up colonoscopy for a definitive diagnosis and to determine the tumor’s location, crucial for deciding the treatment approach.
Biachi notes the limitation of the blood test in detecting early-stage polyps, crucial for treatment at the most curable stages, as these polyps don’t release the tumor DNA that the test detects.
The effectiveness of the test in identifying precursor polyps and early cancer remains a concern, as pinpointing these lesions is critical for impactful intervention, according to Shaukat.
The Food and Drug Administration is expected to review the Shield blood test for approval within the year, as reported by Guardant Health. If approved, the test would be administered every three years starting at age 45, while individuals with symptoms or a family history of colon cancer would still require a colonoscopy.