Multicancer early detection (MCED) tests - an overview of technologies and clinical evidence

Early detection of cancer is one of the key factors influencing patient prognosis and overall cancer-related mortality. However, current population--based screening programs are limited to only a few selected diagnoses, and many highly lethal malignancies still lack an effective option for early detection. Multicancer early detection (MCED) tests represent a new group of blood-based screening methods aimed at identifying the presence of early-stage cancer across multiple primary sites through a single peripheral blood sample. They mainly rely on the analysis of circulating tumor DNA, including its methylation and fragmentation characteristics, or on combinations with protein markers or the detection of circulating tumor cells. These tests offer high specificity and are able to estimate the most likely site of origin of the tumor, which is crucial for guiding subsequent diagnostic workup. At present, the largest body of evidence is available for methylation-based and multiomic platforms. Prospective studies conducted so far in asymptomatic individuals suggest that MCED tests may enable the detection of cancers at clinically relevant stages, with a relatively low false-positive rate and an acceptable burden of follow-up investigations. At the same time, important limitations remain particularly lower sensitivity in the earliest stages of disease, the absence of standardized diagnostic algorithms following a positive result, and the lack of evidence for an effect on cancer-specific mortality and the incidence of advanced-stage disease. MCED tests therefore cannot yet be considered a replacement for established organ-specific screening programs. However, they appear to be a promising complement to current screening strategies, particularly for the detection of cancers for which no established screening exists. Their future clinical role will depend on the results of large prospective and randomized studies demonstrating their true benefit for both the population and healthcare systems. In addition to strong evidence of clinical benefit, widespread implementation into clinical practice will also require standardization of downstream diagnostic pathways and careful health-economic evaluation.