Abstract 2413: Mutated TP53 prevalence in EGFR -mutated advanced non-small cell lung cancer patients with brain metastases

Abstract Introduction: Approximately 50% of patients with EGFR-mutated advanced non-small cell lung cancer (NSCLC) develops brain metastases (BM), which is associated with a poor prognosis. Mutations in TP53 are associated with earlier development of resistance to EGFR tyrosine kinase inhibitors, but it is unclear whether patients who develops BM have a higher prevalence of TP53 mutations. Analyses of circulating tumor DNA (ctDNA) in blood have been established as a good alternative to tissue biopsies to assess the genomic landscape of NSCLC. In this study, we aim to analyze ctDNA from patients with advanced EGFR-mutated NSCLC to investigate the prevalence of TP53 mutations in patients with BM, and to explore whether patients with BM exhibit a distinct ctDNA profile compared to patients without. Materials and Methods: Plasma samples collected before treatment commenced from 97 of the 100 patients with EGFR-mutated advanced NSCLC enrolled in the First-line Treatment With Osimertinib in EGFR-mutated Non-small Cell Lung Cancer study (The FIOL study: NCT03804580) were analyzed. Patients were split into cohorts with (n=44) and without BM (n=53) at baseline. The cell-free DNA was isolated and sequenced with targeted next-generation sequencing with the AVENIO ctDNA Surveillance Panel (Roche) containing 197 lung cancer-related genes. Results: Mutations in ctDNA were found in 83 patients (85.6%), with 6 patients with BM having no ctDNA mutations and 8 patients without BM having no ctDNA mutations. Besides EGFR mutations, TP53 was the most frequently mutated gene, with 42 patients (43.3%) harboring TP53 mutations. There was no significant difference in the prevalence of TP53 mutations between the cohort with BM (n=23) and the cohort without (n=19), (p=0.15). There was no difference in the number of identified mutations in the two cohorts (BM: median: 2 (range: 0-6), without BM: median: 2 (range: 0-11), p=0.71). Patients with BM had a numerically lower ctDNA level (median: 45.5 mutant molecules/mL), than patients without BM (median: 75.9 mutant molecules/mL), though the difference was not statistically significant (p=0.68). Conclusion: Prevalence of TP53 mutations in plasma collected before osimertinib treatment initiation in advanced EGFR-mutated NSCLC was similar between patients with and without BM at baseline. Furthermore, there was no difference in the ctDNA profile between these two cohorts. Future experiments will clarify the impact of TP53 mutations in patients with or without BM. Citation Format: Simone Stensgaard, Inger Johanne Z. Eide, Elin Marie Stensland, Åslaug Helland, Simon Ekman, Karin H. Hansen, Saulius Cicenas, Bjørn Henning Grønberg, Peter Meldgaard, Boe S. Sørensen, Odd Terje Brustugun. Mutated TP53 prevalence in EGFR-mutated advanced non-small cell lung cancer patients with brain metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2413.