Clinical significance of clonal hematopoiesis in the interpretation of blood liquid biopsy

As the use of next‐generation sequencing (NGS) for plasma cell‐free DNA (cfDNA) continues to expand in clinical settings, accurate identification of circulating tumor DNA mutations is important to validate its use in the clinical management for cancer patients. Here, we aimed to characterize mutations including clonal hematopoiesis (CH)‐related mutations in plasma cfDNA and tumor tissues using the same ultradeep NGS assay and evaluate the clinical significance of CH‐related mutations on the interpretation of liquid biopsy results. Ultradeep targeted NGS using Oncomine Pan‐Cancer Panel was performed on matched surgically resected tumor tissues, peripheral blood cells (PBCs), and 120 plasma cfDNA samples from 38 colorectal cancer patients. The clinical significance of the CH‐related mutations in plasma cfDNA was evaluated by longitudinal monitoring of the postoperative plasma samples. Among the 38 patients, 74 nonsynonymous mutations were identified from tumor tissues and 64 mutations from the preoperative plasma samples. Eleven (17%) of the 64 mutations identified in plasma cfDNA were also detected in PBC DNA and were identified to be CH‐related mutations. Overall, 11 of 38 (29%) patients in this cohort harbored at least one CH‐related mutation in plasma cfDNA. These CH‐related mutations were continuously detected in subsequent postoperative plasma samples from three patients which could be misinterpreted as the presence of residual disease or as lack of treatment response. Our results indicated that it is essential to integrate the mutational information of PBCs to differentiate tumor‐derived from CH‐related mutations in liquid biopsy analysis. This would prevent the misinterpretation of results to avoid misinformed clinical management for cancer patients.