Abstract 1956: Comparison of somatic variations between circulating tumor DNA and paired tissue in 1,111 pan-cancer patients

Abstract Circulating tumor DNA (ctDNA) offers a noninvasive method to assess tumor-specific mutations. This retrospective study investigated the concordance of genomic variations between ctDNA and tissue and its influence factors. Paired blood and tissue samples were collected from 1, 111 patients with ten tumor types and underwent sequencing of 425 genes. We evaluated the relationship between the concentration of cell-free DNA (cfDNA), sensitivity of ctDNA, mutation landscape, variant allele frequency, and various clinical parameters. The median concentration of cfDNA and overall sensitivity of ctDNA was 16.8 ng/ml and 61.5%, which correlated positively with clinical stage and tumor diameter and negatively with treatment response. The overall concordance rate of genomic alterations between ctDNA and tissue was 24.6%. The top five altered genes and pathway-based disruption signatures identified by ctDNA profiling were similar to tissue. For mutations with a normalized allele frequency less than 0.2, the proportion of ctDNA-specific mutations was higher than concordant mutations (61.5% and 9.7%). Advanced clinical stage, large tumor diameter, poor treatment response, the presence of liver metastasis, and impaired liver function lead to a high concordance rate. Patients with ctDNA-positive status, subclonal mutations, and more ctDNA-specific mutations had shorter overall survival than those with ctDNA-negative status, no subclonal mutations, and fewer ctDNA-specific mutations, respectively. In conclusion, a higher concordance rate of somatic variations between ctDNA and tissue indicated an advanced clinical stage, larger tumor size, worse treatment response, and presence of liver metastasis. Subclonal or more ctDNA-specific mutations detected were associated with poor prognosis. Citation Format: Meng Zhang, Yi Feng, Xue Du, Changda Qu, Meizhu Meng, Meiying Ye, Min Liang, Ziran Yang, Wenjuan Gong, Xingyu Ma, Jialiang Guo, Wenmei Li, Chenxuan Wang, Qiuxiang Ou, Sha Wang, Haimeng Tang, Shuqin Jia. Comparison of somatic variations between circulating tumor DNA and paired tissue in , pan-cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1956.