Incidence of Androgen Receptor and DNA Repair Gene Mutations in Advanced Solid Malignancies: Clinical Impact of Liquid Biopsy at Veteran Affairs Medical Center

Introduction/Objective The advent of Liquid biopsy targeting genetic mutations in solid tumors is a major milestone in field of precision oncology. This minimally invasive, novel revolutionary technique analyses circulating tumor cells (CTC) in peripheral blood and detects signature genomic alterations. DNA repair gene (DDR) mutations have been reported in 25-40% of prostatic cancers and >50% of non-small cell lung cancers (NSCLC), being more common in late-stage and hormone refractory prostate cancers. One of the DDR, especially Tp53 has been found to be associated with poor prognosis and increased germline mutations. We herein present a quality assurance study to determine feasibility of liquid biopsy for personalized management in veterans for advanced solid malignancies and its clinical impact. Methods Quality assurance documentation from Foundation One (Cambridge MA, NGS) on liquid biopsies performed for the Corporal Michael J. Crescenz Veteran Affairs Medical Center (CMCVAMC) from May 2019 to April 15, 2020 were reviewed. Statistical data for adequacy, cases with notable mutations, frequency and type of mutations of AR, DNA damage repair (DDR) gene and Tp53 were noted. Results A total of 31 liquid biopsies were performed over this time period, of which 29/31 (93.50%) were adequate for evaluation. 23/29 (79.30%) showed notable mutations, in 4/23 (17.39%) guided treatment decisions based on androgen receptor (AR) amplification, and 7/29 (24.1%) of all cases showed DDR gene mutations indicating poor outcome and resistance to the current therapy. Greater than 50% (16/29 (55.7%)) of the veterans with advanced cancers harbored Tp53 mutation, which instills hope and future insight for patient tailored oncologic therapy. Conclusion The minimally invasive liquid biopsy shows a great promise as a diagnostic and prognostic tool in the personalized clinical management of advanced prostate and NSCLC in veteran patient population with unique demographic characteristics. Difference in frequency of the genetic mutations (DDR, TP53, AR) in this cohort provides valuable information for disease progression, lack of response, mechanism of resistance to the implemented therapy and clinical decision making. Precision oncology can be further tailored for this cohort by focusing on DNA repair genes and Tp53 in future for personalized targeted therapy.