Genomic diversity between primary tumor tissue and tumor circulating cell-free DNA (cfDNA) in patients (pts) with metastatic prostate cancer.

189Background: Tumor tissue and tumor cfDNA next-generation sequencing (NGS) tests are obtained in pts with metastatic prostate cancer and have demonstrated a diverse genomic landscape. High-level evidence does not exist for utilizing these tests to guide treatment selection in these pts. Targeted therapies are available for metastatic prostate cancer treatment and clinical trials are investigating drugs targeting specific molecular pathways. The objective of this study was to assess type and number of genomic aberrations between tumor tissue and cfDNA. Methods: Pts with metastatic prostate cancer who had both tissue and cfDNA results were selected and genomic profiles were compared between these two technologies. The mean number of tissue mutations was compared to cfDNA mutations for all pts using the t-test. The mutations for both tests were then categorized into five pathways: DNA repair, cell cycle regulation, PI3K, epigenetics, and androgen receptor (AR). For each pathway, the total number of patient...