Private somatic mutations identified with liquid biopsy lead tumor progression in solid cancers

Aim: Primary tumors can be divided into oncogene-addicted (e.g., lung) and non-oncogene addicted (e.g., breast). Only the former group has an Achilles-heel single gene for successful target therapy, whereas the latter has mutations of multiple causative genes. Currently, tissue biopsy used for genetic surveys do not give a complete picture of the molecular profile and clonal evolution, but only provide static information over time.Methods: A series of 133 patients with 16 different solid tumors were enrolled. Blood samples were collected and cell-free DNA (cfDNA) was extracted. cfDNA libraries were analyzed using AVENIO circulating tumor DNA (ctDNA) Expanded Kit and Illumina NextSeq 550 for sequencing was used. In order to evaluate the clinical evolution over time, a second cfDNA analysis was performed after a mean interval of 2 months.Results: Through the cfDNA liquid biopsy, we found 89 pathogenic variants in 54 genes. Breast, lung, and prostate cancers showed the largest number of mutated genes. TP53, PIK3CA, FGFR3, KRAS, and ERBB2 were the most frequently mutated genes among 16 different tumors. Gene distribution didn’t show any type of prevalence. In particular, every patient with disease progression seems to have a “private” combination of gene pair mutations, with TP53 as the most frequently mutated gene.Conclusion: We showed that the clonal evolution of tumors includes a private combination of genes, regardless of tumor type. In the future, the cancer treatment can be the targeted therapy against specific tumor mutation(s). The present approach seems promising to both identify key cancer genes and follow clonal evolution over time