FDA Approves Blood Test for CRC

What is CRC?

Colorectal Cancer (CRC) is a cancer that affects the colon or rectum. Accounting for almost 10% of all cancer cases worldwide, it remains the third most common form of cancer and second predominant cause of cancer related deaths. This type of cancer is difficult to detect in earlier stages as symptoms are not as apparent. Hence, regular screening is recommended, and various tests are offered such as stool tests, flexible sigmoidoscopy, colonoscopy, and CT colonography. Individuals primarily at risk are:

1. People older than 50 years. 

2. Family history of colorectal cancer or genetic conditions such as Lynch syndrome, familial adenomatous polyposis, or colorectal polyps.

3. Personal history of colorectal cancer or a specific type of polyps.

4. Inflammatory bowel diseases such as Crohn’s disease.

5. Lifestyle choices such as obesity, smoking, excessive drinking, and more.

Individuals diagnosed with colorectal cancer have a couple options for treatment such as surgery, radiotherapy, chemotherapy, targeted therapy, and immunotherapy.

However, it is imperative to emphasize the role of regular screening. Since earlier stages of this cancer show no symptoms, it is harder to detect. Most importantly, the earlier CRC is found, the more treatable it is.

What is Shield?

Guardant Health has developed a blood test called Shield which can be used to detect colorectal cancer. Guardant Health cites, 3 in 4 individuals who die from CRC are not up to date with their screening. More importantly, they also cite if CRC is detected at an early stage, the 5-year survival rate is 94%. However, once the cancer spreads to distant regions of the body, the 5-year survival rate dramatically drops to 14%. This blood test can aid in making screening more accessible to a larger population. 

Many people avoid regular screening methods because they are time consuming and feel unpleasant. But Shield, through a simple blood draw, presents a non-invasive procedure that can detect alterations caused by colorectal cancer in the blood. The test has been available since 2022, however laboratories have had to pay a self-pay price of $895. But Guardant expects that the Shield blood test will be covered by Medicare as it covers performance requirements. 

How does Shield work?

Cancer cells and polyps shed DNA fragments, which the Shield test detects. First, it assesses the ctDNA which refers to the DNA shed by the tumers. It also analyzes which genes are turned on/off through the entire genome and analyzes the size of the ctDNA fragment. Finally, it detects the expression of certain proteins which are associated with cancer. A culmination of all these results can indicate either normal signal or abnormal signal. In a study published by the New England Journal of Medicine, the test was found to have an 83% specificity rate, which indicates its accuracy in identifying people with the disease. The test has its limitations in that it only detected 13% of large polyps as opposed to the 95% detection rate by colonoscopies. 

A committee that advises the FDA suggested approving the Shield test because while there are many limitations such as its serious inability in prevention, the Shield blood test can signal people to get screened. Major inconveniences surrounding regular screening can prompt individuals to avoid it. For example, colonoscopies require fasting and the consumption of a laxative to cleanse the colon the day before. Accompanied with the required anesthesia during the procedure and most likely a day off work, many people avoid screening putting them at risk of later detection. The hope presented by the Shield blood test is that more people will be prompted to get screened. CRC is responsible for the death of 53,000 individuals and through earlier detection, CRC is highly treatable. On July 29, 2024, the FDA approved Guardant Health’s Shield Blood Test.

Works Cited:

CDC. “Screening for Colorectal Cancer.” Colorectal Cancer, 9 May 2024, www.cdc.gov/colorectal-cancer/screening/index.html.

“Guardant Health.” Guardant Health, guardanthealth.com/wp-content/uploads/Guardant_Shield_FactSheet-1.pdf. Accessed 30 July 2024.

“Https://Investors.guardanthealth.com/Press-Releases/Press-Releases/2024/Guardant-Healths-Shield-Blood-Test-Approved-By-FDA-As-a-Primary-Screening-Option-Clearing-Path-For-Medicare-Reimbursement-And-a-New-Era-of-Colorectal-Cancer-Screening/Default.aspx.” Guardant Health, 29 July 2024, investors.guardanthealth.com/press-releases/press-releases/2024/Guardant-Healths-Shield-Blood-Test-Approved-by-FDA-as-a-Primary-Screening-Option-Clearing-Path-for-Medicare-Reimbursement-and-a-New-Era-of-Colorectal-Cancer-Screening/default.aspx. Accessed 30 July 2024.

Kolata, Gina. “F.D.A. Approves Blood Test for Colon Cancer Detection.” The New York Times, 29 July 2024, www.nytimes.com/2024/07/29/health/colon-cancer-blood-test-shield.html. Accessed 30 July 2024.

Leo, Leroy. “Reuter.” Reuters, 29 July 2024, www.reuters.com/business/healthcare-pharmaceuticals/us-fda-approves-guardant-healths-blood-based-cancer-test-2024-07-29/. Accessed 30 July 2024.

World Health Organization. “Colorectal Cancer.” World Health Organization, 11 July 2023, www.who.int/news-room/fact-sheets/detail/colorectal-cancer.

Images:

Image 1: “Colorectal Cancer: Symptoms, Causes, and Treatment.” Scientific Animations, 19 July 2019, www.scientificanimations.com/colorectal-cancer-symptoms-causes-treatment/.

Image 2: “Https://Investors.guardanthealth.com/Press-Releases/Press-Releases/2024/Guardant-Healths-Shield-Blood-Test-Approved-By-FDA-As-a-Primary-Screening-Option-Clearing-Path-For-Medicare-Reimbursement-And-a-New-Era-of-Colorectal-Cancer-Screening/Default.aspx.” Guardant Health, 29 July 2024, investors.guardanthealth.com/press-releases/press-releases/2024/Guardant-Healths-Shield-Blood-Test-Approved-by-FDA-as-a-Primary-Screening-Option-Clearing-Path-for-Medicare-Reimbursement-and-a-New-Era-of-Colorectal-Cancer-Screening/default.aspx. Accessed 30 July 2024.

Image 3: “Guardant Health.” Guardant Health, guardanthealth.com/wp-content/uploads/Guardant_Shield_FactSheet-1.pdf. Accessed 30 July 2024.