Circulating tumor DNA in identifying resistant subclones post EGFR blockade: Implications for EGFR rechallenge.

• DOI: 10.1200/jco.2021.39.3_suppl.131
• Publication Date: 2021-01-22T19:59:19Z
• Authors: Adithya Chennamad...; Pashtoon Murtaza ...
• Keywords: EGFR Inhibitors; Circulating tumor DNA; Targeted Therapy

131 Background: For patients with metastatic RAS/RAF wild-type refractory colorectal cancer anti-EGFR therapy can be reused in subsequent lines of therapy. However, it is not entirely clear if all derive benefit. Increasingly been recognized that these acquire mechanisms resistance which detected on circulating tumor DNA-based testing. We present a series who had serial testing post EGFR showing its feasibility and value. This would have implications for rechallenge. Methods: reviewed records initially were noted to tissue Wild type received prior then subsequently at least 1 Included result comprehensive NGS based profiling both as well ctDNA. Results: Median duration initial anti was around 10 months. Table shows results patient's genomic parallel the done later when being decided. As noted, known acquired 100% cases. These included KRAS, NRAS, extracellular domain mutations BRAF mutations. Interestingly levels sub-clones expressed variant allele fraction percentage varied decreased over time relation timing exposure. Additionally, polyclonal number clones also including some disappearing during non-EGFR (EGFR holiday). Conclusions: Patient's blockade may multiple easily noninvasive liquid biopsies. likely will benefit from rechallenge recently reported CRICKET (NCT02296203) CAVE (EudraCT number: 2017-004392-32) clinical trials. Rechecking biopsy plasma status one thing incorporated into practice only are absent. [Table: see text]