Blood Test for Colon Cancer May Soon Be FDA Approved (2024)

A new blood test can accurately detect 5 out of 6 cases ofcolorectal cancer, according to a study published March 14, 2024, in The New England Journal of Medicine.The Shield blood testrequires less prep and fewer steps than current colorectal cancer screening options.

“That accuracy rate is close to at-home stool tests used for early detection of colorectal cancer,” says the corresponding author William M. Grady, MD, a gastroenterologist at Fred Hutch Cancer Center in Seattle. The blood-based test could offer an alternative for patients who might decline current screening options, says Dr. Grady.

On May 23, an advisory panel for the U.S. Food and Drug Administration (FDA) voted in favor of approving the test, per Everyday Health’s network site, MedPage Today. The panel voted in support of the test's safety by 8-1, in support of its effectiveness by 6-3, and in support of its benefit-risk profile by 7-2.

The FDA typically follows the advice of its advisory committees. FDA approval could clear the way for insurance and Medicare coverage.

How Important Is This New Colorectal Cancer Screening Method?

An additional screening option for colorectal cancer is a good thing, says Sean Langenfeld, MD, a colorectal surgeon at Nebraska Medicine in Omaha, who was not involved in the study.

“Colorectal cancer is common, deadly, and preventable. It’s the third most common cancer and the second leading cause of cancer-related death,” he says.Despite this, only about 60 percent of the public actually go through with appropriate screening, says Dr. Langenfeld.

The FDA advisory committee noted that the blood test has a few limitations. “It's a good colon cancer screening test, but for later-stage colon cancer," said Karla Ballman, PhD, of the Mayo Clinic College of Medicine and Science in Rochester, Minnesota, in her interview with MedPage Today. “It’s not as good in stage 1, and definitely not good for advanced adenoma [precancerous lesions].”

The Shield test is only available with a doctor’s prescription. Since its launch in May 2022, it’s been used by more than 20,000 people. Most people likely pay for it out of pocket, at a price of $895.

Early Detection of Colorectal Cancer Saves Lives

The rate of colorectal cancer has steadily decreased over the past couple of decades, although colorectal cancer rates are on the rise for younger adults. The number of people under 55 who are newly diagnosed with colorectal cancer has nearly doubled in the past 30 years.

When colorectal cancer is found at an early stage, before it has spread, the five-year relative survival rate is 91 percent. But if the cancer has spread to distant parts of the body, the survival rate drops to just 13 percent.

“Having a blood-based screening test available will lead to more patients agreeing to undergo screening and hopefully improve screening rates, as they see it as less invasive,” says Langenfeld.

Blood Test Accuracy Measured Against ‘Gold Standard’ Colonoscopy

To compare the accuracy of the blood test to a colonoscopy, the current gold standard for colorectal cancer screening, researchers enrolled nearly 8,000 people between the ages of 45 and 84 years old. Participants were 60 years old on average, and 54 percent were women. Among the participants, 78.5 percent were white, 12 percent were Black, and 7 percent were Asian. About 13 percent identified as Hispanic or Latino. The racial and ethnic makeup of the group aligns with the demographics in the 2020 U.S. Census, according to the authors.

In order to be included in the study, participants could only have an “average risk” for colorectal cancer, which is the intended user group for the blood test. That means they had no family history of colorectal cancer, no personal history of cancer, and no diagnosis of inflammatory bowel disease or large polyps.

A total of 7,861 people met all those criteria and completed a colonoscopy as well as the blood test. Out of 65 participants with colonoscopy-detected colorectal cancer, 54 of them also had a positive result (indicating cancer) with the blood test — meaning that the blood test didn’t detect 11 out of 65 cases. That translates to an accuracy rate of about 83 percent.

The test was better at identifying colorectal cancers, including early stage cancers, but less accurate in detecting advanced precancerous lesions, which can turn into cancer over time.

How Does the Shield Test Measure Up to Currently Available Options?

A colonoscopy is the most reliable way to identify polyps and colorectal cancer, but it does require several steps: You must follow a special diet, clean out the bowels with laxatives, and then undergo the procedure itself, which requires sedatives, anesthesia, or pain medicine and a ride home.If nothing unusual is found during the procedure, it needs to be done only every 10 years.

In addition to the Shield blood test, there are two main at-home tests for colorectal cancer.

  • The FIT, which stands for fecal immunochemical test, is about 79 percent accurate in detecting colon cancer. The test comes as a kit, with instructions and materials to safely and hygienically collect a small amount of fecal matter (poop) to be sent to the lab for analysis. It’s recommended that the test be repeated every one to two years.
  • Cologuard (fecal DNA testing) has a 92 percent accuracy rate.It also involves collecting a sample and mailing it off, and the test should be repeated every three years.

The accuracy of the Shield blood test in detecting colorectal cancer is very similar to current stool-based tests, including FIT, but somewhat below the sensitivity of fecal DNA testing like Cologuard, says Langenfeld. It had a specificity of 90 percent — meaning this test was not setting off many false alarms, he adds.

The Shield test needs to be repeated every three years. If a person gets a positive test result, a colonoscopy is recommended to determine if the test result is a true or false positive.

Who Should Use the Shield Colorectal Cancer Test?

“This test is most appropriate for patients unable or unwilling to undergo colonoscopy — that’s who I would recommend it to. Since it is fast, easy, and noninvasive, it will seem like less of a commitment, and will hopefully lead to people undergoing screening who would have otherwise continued to put it off for the foreseeable future,” says Langenfeld.

That being said, the test wasn’t good at picking up precancerous lesions — it identified them only 13 percent of the time. "I will still recommend screening colonoscopy for most patients," he adds.

Polyps are common, especially in older adults, and most are benign, meaning noncancerous. But sometimes polyps can change into cancer — usually over many years. Another benefit of a colonoscopy is that precancerous polyps can be removed during the procedure, says Langenfeld.

Grady recommends talking with your provider about which option is best for you. Currently, when people are given the option of doing a colorectal cancer screening with a stool-based test or with colonoscopy, nearly half of people elect to do neither, he points out.

When Do I Need to Start Getting Screened for Colorectal Cancer?

Both the American Cancer Society and the U.S. Preventive Services Task Force recommend that people at average risk start screening at age 45. If you have health insurance, you may not even need to pay a deductible or copay. Find out more by visiting the Centers for Disease Control and Prevention’s page on colorectal cancer screening.

Blood Test for Colon Cancer May Soon Be FDA Approved (2024)


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