ATM mutation

Hi all,

My mom's Caris report showed ATM mutation with "variant frequency" of 52% (EGFR was 59% and PTEN was 17%). Her doctor is suggesting HDAC drug/belinostat trial. Has anyone seen ATM mutation on their genetic report? Is it common in GBM? We may switch her from Keppra to valproic acid as it is also a HDAC drug, or give her both. Thank you for your help!