Multicancer Early Detection Tests at a Crossroads: Commercial Availability Ahead of Definitive Evidence

Multicancer early detection tests (MCEDs), sometimes referred to as liquid biopsies, are tests that can screen for multiple cancers by analyzing blood, urine, and other bodily fluids for biomarkers released by cancer cells. These tests have the potential to change the cancer screening paradigm if they are shown to reduce cancer mortality. However, it is not yet known whether MCEDs reduce mortality. Randomized controlled trials, the gold standard for evaluating cancer screening programs, are currently evaluating the effectiveness of MCEDs. However, because cancer-specific and all-cause mortality are end points that can take years to reach, trials are being designed with surrogate end points such as stage of disease at detection. However, the correlation between cancer stage and survival appears to vary by cancer type, and many have argued that trials must also continue to follow for the gold standard of mortality end points until these surrogate end points are appropriately validated. The widespread use of MCEDs before conclusive evidence supporting their use has the potential to cause harm to patients, could widen health inequities, and further drive health care costs. Consequently, providers should engage in shared decision making regarding MCED tests with patients who inquire about MCEDs emphasizing that MCEDs should be additive to, not replacements for, the currently recommended cancer screening tests.