Working Paper Article Version 1 This version is not peer-reviewed

Genomic Landscape of Patient-matched Tumor and Circulating Cell-free DNA in Metastatic Melanoma

Version 1 : Received: 3 October 2019 / Approved: 4 October 2019 / Online: 4 October 2019 (10:35:02 CEST)

How to cite: Diefenbach, R.; Lee, J.; Strbenac, D.; Yang, J.; Menzies, A.; Carlino, M.; Long, G.; Spillane, A.; Stretch, J.; Saw, R.; Thompson, J.; Ch'ng, S.; Scolyer, R.; Kefford, R.; Rizos, H. Genomic Landscape of Patient-matched Tumor and Circulating Cell-free DNA in Metastatic Melanoma. Preprints 2019, 2019100045 Diefenbach, R.; Lee, J.; Strbenac, D.; Yang, J.; Menzies, A.; Carlino, M.; Long, G.; Spillane, A.; Stretch, J.; Saw, R.; Thompson, J.; Ch'ng, S.; Scolyer, R.; Kefford, R.; Rizos, H. Genomic Landscape of Patient-matched Tumor and Circulating Cell-free DNA in Metastatic Melanoma. Preprints 2019, 2019100045

Abstract

The use of circulating cell-free (cf) DNA to monitor cancer progression and response to therapy has significant potential but there is only limited data on whether this technique can detect the presence of low frequency subclones that may ultimately confer therapy resistance. In this study, we sought to evaluate whether whole-exome sequencing of cfDNA can accurately profile the mutation landscape of metastatic melanoma. We used whole-exome sequencing (WES) to identify variants in matched tumor-derived genomic (g) DNA and plasma-derived cfDNA isolated from a cohort of 10 metastatic cutaneous melanoma patients. WES parameters such as sequencing coverage and total sequencing reads were comparable between gDNA and cfDNA. There was significant concordance between gDNA and cfDNA based on the total number of variants identified and the degree of overlap in variants which was independent of the site of tumor biopsy. The mutant allele frequency of common single nucleotide variants was lower in cfDNA reflecting lower read depth and dilution of circulating tumor DNA in the circulation by other cfDNA species. In addition to known melanoma driver mutations, several other melanoma-associated mutations were found to be concordant between matched gDNA and cfDNA. This study highlights that WES of cfDNA can capture clinically-relevant mutations present in melanoma metastases, but does not appear to provide any additional unique information on tumor heterogeneity. Targeted deep sequencing may be required to detect low frequency genomic aberrations known for predicting therapy resistance.

Subject Areas

whole exome sequencing; melanoma; circulating tumor dna

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