Cancer blood tests are everywhere. Do they work?

9 hours ago

Cancer blood tests, like Galleri, claim to detect early signs of over 50 cancer types but lack extensive randomized controlled trials (RCTs) and regulatory approval.
The first RCT for Galleri, conducted with the UK NHS, did not meet its goal of reducing late-stage cancer diagnoses when used alongside existing screening programs.
Liquid biopsy tests, similar to MCEDs, are already used for monitoring cancer progression but detecting early-stage cancer remains challenging due to low tumor DNA levels in blood.
MCED tests have high specificity (96–99.5%) but variable sensitivity (30–80%), meaning they can miss many cancers or provide false positives.
Some researchers believe MCED tests could revolutionize cancer detection, especially for cancers without existing screening tools, while others warn of risks like false diagnoses and unnecessary procedures.
Current screening programs detect only 14% of cancers in the U.S., highlighting the need for better early detection methods.
MCED tests analyze biomarkers like DNA methylation patterns and genetic mutations in blood samples to identify multiple cancer types.
Trials evaluating MCED tests focus on sensitivity, specificity, and positive predictive value, but many have only been tested in controlled settings, not broader populations.

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