While we cannot definitively rule out sampling bias as an explanation for these findings, we believe this is less likely, given the lack of spatial heterogeneity of other genetic alterations analyzed, conservation of negative CDKN2A deletion status in one patient who had this testing performed on paired metastatic tumor samples, and evidence of spatial preservation of CDKN2A deletions from intratumoral genomic studies in glioblastoma [42, 56]. This evidence concerns the gene CDKN2A and glioblastoma.