A new blood test that screens for colon cancer has just been approved by the Food and Drug Administration (FDA).
The blood sample required for the new test, called Shield, can be obtained by appointment with a doctor or in a commercial laboratory. The hope is that the test can increase the number of people diagnosed with colorectal cancer the second leading cause of cancer-related diseases in the US
Shield is not considered an alternative to colonoscopies for diagnosing this disease. Rather, it is a non-invasive way to flag if someone may have cancer so that they can be screened for further screening. The new test has been approved for adults aged 45 and over with a normal risk of colon cancer.
The five-year survival rate for colorectal cancer is very high – more than 90% – when it is caught in its early stages, but that survival decreases in advanced stages. Case studies show that, if gaps in colorectal cancer screening were closed, about 70% of related diseases are preventable.
Related: Gut bacteria associated with colorectal cancer in young adults
Recent data suggest that more than 1 in 3 eligible adults they are not diagnosed during their colorectal cancer screening.
“The continuing gap in colorectal cancer screening rates shows that existing screening options are failing millions of people,” Dr. Daniel ChungGastroenterologist at Massachusetts General Hospital and professor of medicine at Harvard Medical School, said in a statement from Shield manufacturer, Guardant Health. The Shield test offers a “compelling new solution to close this gap,” he argued.
Shield works by checking the blood for pieces of DNA shed by cancer cells and polyps, which are growths of cells in the colon that can be dangerous. In the results of the trial published in New England Journal of Medicine, the test was 83% sensitive for colon cancer, meaning it correctly identified the cancer most of the time. It missed 17% of colorectal cancer cases.
In one test, 10% of people without colon cancer got a false positive – so the test is not perfect, but it is comparable to diagnostic tests that involve taking a stool sample.
A clinical trial also found that Shield is not good at detecting advanced cancerous polyps; saw them in only 13% of cases. That is why the test will not be a suitable place for many tests, such as colonoscopieswhich involve using a long, thin scope to examine the entire colon and are very useful for finding polyps.
So, a person diagnosed with cancer in the Shield test will need a follow-up colonoscopy to confirm the type of cancer and find tumors.
Current guidelines recommend that people are first screened for colon cancer at the age of 45, if they are at risk of the disease. There are several options for screening: Stool-based tests should be used annually or every one to three years, depending on the specific test used, while colonoscopies are recommended every other year and another 10. A less frequently used test in the US, called flexible sigmoidoscopy, is recommended every five years.
The shield would be awarded every three years, NBC News reported.
Now approved, Shield is the second colon cancer test to be approved by the FDA. However, the first, Epi proColon, not covered by Medicare because of the concern about its accuracy and benefits. It is expected that Medicare and private insurance will cover the Shield, the list of which has yet to be announced.
The new test is an “acceptable process,” Dr. Arvind Dasariassistant professor in the Department of Gastrointestinal and Medical Oncology at the University of Texas MD Anderson Cancer Center, told NBC News.
However, “we will have to wait and see what the impact will be in terms of improving diagnosis and reducing the mortality rate,” he said.
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