Can Blood Tests Really Detect Cancer Early? A 4-Year Clinical Trial Aims to Find Out

What if a blood test could detect the earliest traces of cancer in your body before you display any signs or symptoms?

Such tests that make these claims exist, but they’re expensive and not authorized by the Food and Drug Administration (FDA). They’re called multi-cancer early detection (MCED) tests.

Soon, the National Cancer Institute will give these blood tests a thorough evaluation, paving the way to wider accessibility if proven effective.

Last month, President Biden highlighted this initiative, called the Vanguard Trial, as a crucial piece of his administration's Cancer Moonshot Initiative.

Beginning in 2024, the Vanguard Trial will follow 24,000 participants over four years. Researchers are seeking to learn about any potential benefits and harms of MCED tests, the impact of early detection from MCED tests on cancer survival and death rates, and the most prudent course of action to take following a positive MCED test.

If the Vanguard Trial shows that MCED tests are beneficial at detecting cancer in its earliest stages, then a 225,000-participant, randomized control trial will follow.

What Are MCED Tests?

Right now, screening tests exist for only five types of cancer:

• Breast cancer: Mammogram or MRI
• Cervical cancer: Pap smear or HPV test
• Colorectal cancer: Colonoscopy, fecal occult blood test, sigmoidoscopy, or DNA stool test
• Lung cancer: Low-dose computed tomography (chest CT scan)
• Prostate cancer: Prostate specific antigen (PSA) blood test

MCED tests are minimally-invasive blood tests which aim to discover cancer types that other screening tools cannot, leading to earlier diagnosis and treatment. These cancer types may include bladder, pancreatic, uterine, and kidney cancers, to name a few.

Unlike present cancer screenings such as mammograms or colonoscopies, which only look for one cancer in one area of the body, MCED tests can simultaneously search for multiple types of cancer. They work by detecting the presence of potential cancer markers in the blood before symptoms appear. These markers may include subtle DNA and/or RNA changes, protein biomarkers for cancer, or antibodies against growing cancer cells.

Potential Benefits of MCED Tests

Oncologists and cancer researchers hope that MCED tests will improve cancer outcomes for all individuals by making it easier to find cancers that may presently be undetectable until later stages.

“Carcinogenesis (cancer formation) is a process that takes time. If we have a better understanding of its timeline, then maybe we can think of interventions to prevent cancer from progressing,” Ana Maria Lopez, MPH, MD, professor and interim chair of medical oncology at Sidney Kimmel Medical College, told Verywell.

She added that simple lifestyle changes such as reducing fat in the diet, alleviating stress, increasing physical activity, and improving sleep could halt or even reverse the premalignant process.

Lopez said that research into MCED tests would inform their future use.

“We might recommend people with a high genetic risk profile get tested first,” she said. “Then, it might be people of a certain age. Because we have the possibility of saving lives by detecting cancer earlier in the process, we want to find it as soon as possible.”

Possible Drawbacks to MCED Tests

A positive MCED test result does not automatically mean that you have cancer, but it should prompt further investigation by your clinician to confirm a diagnosis. On the other hand, a negative result does not exclude any possible cancer diagnosis.

The American Cancer Society and the National Cancer Institute warn that large-scale MCED testing could lead to unnecessary medical procedures due to false-positive results. And on the flip side, a negative MCED test might prompt some people to skip out on lifesaving routine medical exams and cancer screenings.

To Make an Impact, MCED Tests Need To Be More Accessible

MCED tests do not have FDA authorization or approval at this time. That means they are not yet widely available to the public or covered by Medicare, Medicaid, or private health insurers.

The only MCED screening test currently available in the U.S. is the Galleri multi-cancer early detection test. Because it does not yet have FDA approval, Galleri is only available by physician order and costs $949.

There are no guidelines at present for who should receive an MCED and when, and typically, people interested in the test must advocate for themselves to a physician. It’s not a home-based test; blood draws must happen at a partner lab facility.

Galleri, created by GRAIL, claims to detect over 50 potential types of cancer, most of which have no other widely-accepted screening method.

“Considering the enormous impact of cancer on society, and the large unmet medical need for unscreened cancers particularly, there is immense excitement in the oncology field for new tests like MCEDs,” Jeffrey Venstrom, MD, chief medical officer at GRAIL, told Verywell via a written statement. “Individuals with elevated cancer risk are best suited for this test, and we currently think that adults aged 50 is the right time to start. For the majority of individuals, annual testing is likely sufficient, although we are studying other ways to administer the test.”

Cancer advocacy organizations like the Prevent Cancer Foundation want greater access to early cancer screenings for all individuals, especially older adults and Medicare beneficiaries, who are at increased risk for developing cancer. They hope that future FDA endorsement will increase the accessibility of these tests to those who will benefit from them the most.

“Having coverage for these tests for Medicare beneficiaries helps address health disparities,” Jody Hoyos, MHA, president and COO of the Prevent Cancer Foundation, told Verywell. “Paying out of pocket creates a significant barrier. It’s critically important to us that once the FDA approves MCED tests, everyone who needs a test has access to them.”

Some individuals in underserved communities may have more difficulty getting routine cancer screenings, Hoyos told Verywell. Cancer disparities occur because of various factors, including systemic racism, lack of trust in the healthcare system, lower screening uptake, and challenges around access to high-quality cancer care.

Less invasive and more easily accessible cancer detection tests will reduce health disparities.

“Early detection saves lives, and the benefits of early cancer detection are not reaching enough people,” Hoyos said.