Validation and Clinical Utility of a Pan-Cancer Circulating Tumor DNA Assay as a First-Approach Test

The feasibility of circulating tumor (ct)-DNA assays in first-approach pan-cancer genomic profiling is not well established. Furthermore, low ctDNA levels limit assay sensitivity, which challenges adaptation to clinical genomic profiling. In this study, a 33-gene next-generation sequencing-based ctDNA panel was validated, and these issues were investigated using real-world clinical data. The cohorts included 123 patients who underwent first-approach ctDNA testing, and 48 patients for whom matched tissue was tested at the same time-point. The overall ctDNA assay failure rate was 0%. Insufficient tumor tissue was the main reason for liquid biopsy (69%). The most common primary cancer profiled was lung (39.0%), followed by colon (13.8%), bile duct (8.9%), pancreas (8.1%), and breast and prostate (each 4.1%). Tier I variants were detected in 33.3% of patients, and Tier I or II variants were detected in 65.0% (including 54.5% cholangiocarcinomas, in which tissue biopsy may be challenging due to anatomic location). Compared with matched tissue, ctDNA showed 76% sensitivity for Tier I variants. Actionable variants were increased by 14.3% with ctDNA versus tissue testing alone. ctDNA results preceded tissue results by an average of 21 days. High feasibility, actionability, and sensitivity support ctDNA assays as a potential first-line genomic test, especially in specific tumor types for advanced tumors with insufficient or unavailable tissue.