Whole exome paraffin sequencing (WEPS) of same-patient (pt) primary, extracranial, and melanoma brain metastases (PEB) to identify new driver and clonal evolution genetic events.

e20033 Background: To date, little is known about how primary melanomas clonally evolve to distant metastases, including brain, and how driver mutations are selected during melanoma progression. To identify new driver and clonal evolution genetic events beyond the known mutations in BRAF/NRAS, we performed WEPS of same-pt PEB. Methods: DNA from tumor (T) and adjacent normal (AN) was extracted from macrodissected tissue slides. DNA libraries were captured using Agilent SureSelect Human All Exon v4 and sequenced at 2x48 bp. Variant calling was performed on T vs. matched AN using VARSCAN (default settings). Single nucleotide variations (SNV) were filtered using prior knowledge (COSMIC). We report only genes having probably or possibly damaging non-synonymous SNV (PolyPhen2 score > 0.45) by ANNOVAR analysis and nonsense mutations. Focused analysis for gene copy number alterations previously described in melanoma was performed using our previously published NGScopy package (Bioconductor). We considered analysi...