Analytical and Clinical Validation of a Circulating Tumor DNA-based Assay for Multi-Cancer Early Detection

10548 Background: The development of multi-cancer early detection (MCED) through a single blood test has emerged as a promising method for improving the efficiency of early cancer detection and benefiting population health. However, the lack of analytical validation and clinical evidence for their utility in diverse populations have prevented their use in clinical practice. To address these challenges, we conducted a comprehensive analytical and clinical validation for an MCED test, SPOT-MAS (Screening for the Presence of Tumor by DNA Methylation and Size). Methods: A prospective cohort study (ClinicalTrials.gov identifier: NCT05227261) was conducted at 13 major hospitals and one research institute in Vietnam. Our study recruited asymptomatic participants aged 40 years or older and followed up for 6 and 12 months. Analytical sensitivity of our assay was assessed by using our healthy and cancer-standard samples with known tumor fraction. The clinical performance was assessed by computing the positive predictive value (PPV), the negative predictive value (NPV) and accuracy in detecting tumor tissue-of-origin (TOO). Results: SPOT-MAS demonstrates the capability to detect at least 50% of cancer samples with a specificity of 98% when the samples have a tumor fraction of 0.049 (95% CI: 0.043-0.059). These results were consistently reproduced in both intra- and inter-batch analyses. Furthermore, our test maintains robustness even in the presence of hemoglobin contamination up to 500 mg/dL and genomic DNA contamination of up to 100%. Our analysis of 10,027 eligible participants demonstrated its ability to detect cancers in asymptomatic individuals with a positive predictive value of 58.14% (95%CI: 43.33- 71.62), an accuracy of 84.00% (95%CI: 65.35-93.60) in predicting tumor location and a negative predictive value of 99.92% (95%CI: 99.83-99.96). Conclusions: To our knowledge, this is the first and largest prospective validation study in Asia supporting the utility of SPOT-MAS as a multi-cancer blood test for early detection in a low- and middle-income country, where a nationwide cancer screening program is urgently needed but currently not available. Clinical trial information: NCT05227261 .