Multi-Cancer Early Detection (MCED) Tests: False Positives & Future Promise

Liquid biopsy - multi cancer detection

An implication of the Cancer Moonshot initiative is new research studying the effectiveness of MCED tests (also known as liquid biopsy tests) to detect multiple types of cancer. MCED measures biological signals that cancer cells may shed in body fluid. The FDA has not approved MCED tests; however, they offer future promise and may be a valuable complementary tool to detecting cancer early or before symptoms arise.

What Should You Know

MCED is not a stand-alone cancer detection tool. A positive MCED result needs confirmation via additional screening and, potentially, a tissue biopsy. A negative finding can miss the presence of cancer, leading to a false-negative test result (NIH, 2023). For now, the MCED tests for about a quarter of cancer types with varying effectiveness and is primarily an out-of-pocket expense. MCED may be worth considering with your doctor as a complement to other cancer screenings and detection if you are interested in exploring evolving cancer detection technology, experiencing subtle or persistent health changes, or have a cancer history.

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Liquid biopsy, also called blood or plasma biopsy, is a minimally invasive diagnostic technique that has gained traction in the field of oncology. Liquid biopsy is still in early trials, and its efficacy is inconclusive. Instead of relying solely on traditional tissue biopsies, which require a surgical procedure to obtain a tissue sample, liquid biopsy extracts vital information about cancer from a patient’s blood. This technique identifies circulating tumor cells (CTCs), DNA/RNA indicators, protein biomarkers, and antibodies, providing potentially valuable insights into cancer development, progression, and treatment response (NIH, 2023).

Blood biopsy tests like the Galleri site about 50 of the ~200 types of known cancers. Routine screenings (4-5 CDC recommended) and the 3 Steps Detect roadmap are still critical in a holistic approach to taking early action on all cancers and increasing early cancer detection. Initial MCED research indicates an overall cancer detection sensitivity that increases with disease stage progression and varies by cancer type and patient attributes. About 40% of patients with a positive Galleri test for cancer actually had cancer (Medscape, 2023). Only time and research will tell if false positive patient results will eventually be diagnosed with cancer. As MCD testing evolves, the test should become more reliable.

Challenges and Promise
While liquid biopsy holds tremendous promise, it is not without challenges. The sensitivity and specificity of the technique can vary depending on the type and stage of cancer. Further research and refinement are necessary. A liquid biopsy is as good as that moment in time and does not indicate a patient’s likelihood of getting cancer in the future. As MCED technology advances, liquid biopsy is expected to play an increasingly significant role in cancer care, enabling better cancer diagnosis and treatment decisions. Additionally, as the cost of liquid biopsy decreases, it may become more accessible to a broader range of patients.

Cancer Survivor and DetecTogether Senior Director of Communications and Engagement Lisa Young said, “While there are challenges to overcome with MCED tests, the continuing research and development in this field hold the promise of better outcomes for cancer patients, offering more hope for a future that DetecTogether strives for every day — where early detection becomes the norm and cancer can be more effectively managed and treated.”


Multi-Cancer Early Detection tests are an exciting advancement in oncology and are considered a complementary tool to patient awareness and action, recommended screenings, and medical and genetic history to detect cancer early. Use DetecTogether’s 3 Steps Detect so you are prepared to take the right actions at the right time to detect cancer early. In a recent survey 23% of our training participants identified a new health issue that needed medical treatment (Impact Study, 2023).


“Blood Test for Multiple Cancers: Many False Positives.” Medscape, Accessed 8 Nov. 2023.

DetecTogether. 2023. Impact Survey Study. Westborough: DetecTogether.

National Institute of Health. Questions and Answers about MCD Tests. detection-mcd-research/questions-and-answers-about-mcd-tests. Accessed 13 Nov. 2023.