After the story on Guardant’s new test for colorectal cancer broke nationally, Craig Eagle, MD, Chief Medical Officer at Guardant Health, kindly weighed in with these exclusive comments for Breaking Cancer News.
Can you briefly please tell us how this technology works?
The Shield test is a qualitative, in vitro diagnostic test intended to detect colorectal cancer-derived alterations in cell-free DNA from blood. It is intended as a screening test for individuals at average risk for the disease, age 45 or older, and is available by prescription from a healthcare provider. The test is not intended for individuals at high risk for colorectal cancer. Shield can be considered in a manner similar to guideline-recommended non-invasive CRC screening options and can be completed during any healthcare visit.
Primary care providers can have patients complete a Shield test with a simple blood draw that requires no advance preparation, providing a convenient and more pleasant alternative screening method that doesn’t require the special preparation, dietary changes, time and discomfort associated with colonoscopy or the unpleasantness of handling stool.
The test result is available approximately two weeks after the sample is received. Patients with a positive Shield result may have colorectal cancer or advanced adenomas and should be referred for colonoscopy evaluation. A negative result indicates that no cancer was detected, but it does not preclude the presence of colorectal cancer, and patients should continue participating in guideline-recommended screening programs. Shield is not a replacement for a diagnostic colonoscopy or for a surveillance colonoscopy in high risk individuals.
Do you have any numbers in terms of how many people have already used this test in a clinical trial?
Between October 2019 and September 2022, more than 20,000 individuals were enrolled in the ECLIPSE study to evaluate the performance of Shield compared to a screening colonoscopy. The study was published in the March 14, 2024 issue of The New England Journal of Medicine.
Since the commercial introduction of the LDT (laboratory developed test) version of the Shield test in May 2022, it has been prescribed for more than 20,000 individuals in a real-world clinical setting. The overall adherence rate for the test has been more than 90%, meaning more than 90% of patients who were prescribed the test completed it. In contrast, studies show only 28-71% of patients who are prescribed other screening methods, such as colonoscopy or a stool test, complete them.
How many years has this test been in trials?
The Shield test was evaluated in the ECLIPSE study, which began in October 2019. Results of the study were published in March 2024.
Can we get an estimate of how many people would benefit from this test?
There are approximately 120 million individuals in the U.S. who are between the ages of 45 and 75 and at average risk of colorectal cancer, and who would thus be eligible for screening with the Shield test. About 50 million of those individuals are not currently up to date with recommended screening.
More than three out of four individuals who die from CRC are not up to date with their screening. Early detection is critical. When colon cancer is found at an early stage before it has spread, the five-year relative survival rate is 91%. If the cancer has spread to distant parts of the body, the five-year relative survival rate is 14%. Shield has the potential to help identify more cancers at an early stage, when they are most treatable.
How early can cancer be detected with this test?
Highlights of the ECLIPSE study results published in The New England Journal of Medicine show that Shield demonstrated 83% sensitivity in detecting individuals with colorectal cancer, including 55-65% for stage I and 100% for stages II, III and IV. These results are on par with the performance of other guideline-recommended non-invasive screening methods, where overall sensitivity in detecting colorectal cancer ranges from 74% to 92%. In the ECLIPSE study, Shield detected approximately 13% of precancerous lesions.
