OR04-5 Circulating Cell-Free DNA-Based Biomarkers For Prognostication and Disease Surveillance in Adrenocortical Carcinoma

Abstract

Abstract Adrenocortical carcinoma (ACC) is a rare aggressive cancer with heterogeneous behaviour. Disease surveillance relies on frequent imaging, which comes with significant radiation exposure. Here, we investigated the role of circulating cell-free DNA (ccfDNA)-related biomarkers for prognostication and monitoring of ACC. We investigated 79 patients with ACC (29M/50F, 52±14yrs; 35 primary tumors [ACC-P] and 44 recurrences [ACC-R]); while 27 patients with adrenocortical adenomas [ACA] (9M/18F, 56±16yrs) and 19 healthy subjects (HS; 9M/10F, 37±9yrs) served as controls. We extracted ccfDNA from 1-4 ml EDTA-plasma using Nonacus Cell3 Xtract or Qiagen QIAamp MinElute kit and quantified by fluorimeter (ccfDNA concentrations, Biomarker 1). Targeted next-generation sequencing (Illumina NextSeq500) was performed in a first subgroup of 52 baseline ccfDNA samples (23 ACC-P, 20 ACC-R, 8 ACA) using a customised panel of 30 ACC-specific genes (Cell3 Target Nonacus). Leucocyte DNA was sequenced to discriminate germline from somatic variants (Biomarker 2). Sequencing data from matched tumor DNA were available for 28 ACC (20 ACC-P, 8 R-ACC). A combined Biomarker score was calculated for prediction of clinical outcome. ACC-P had the highest ccfDNA concentrations (mean±SD 1.08±1.50 ng/µl) compared to ACC-R (0.29±0.23 ng/µl, P<0.05), ACA (0.17±0.13 ng/µl, P<0.005) and HS (0.11±0.07 ng/µl, P<0.005). Using a cutoff of 0.204 (median HS+2SD), 68% of ACC-P were postitive for Biomarker 1 (vs. ACC-R 55%, ACA 28%, HS 5%; P<0.0001 by Chi square test). At ccfDNA sequencing, 43% of ACC-P showed at least one somatic mutation (=positive Biomarker 2), vs. 15% in ACC-R and 0% in ACA. Mutational status at ccfDNA level matched with tumor DNA in 80% of cases. In 23 ACC-P with available sequencing data, the combined Biomarker score was strongly associated with both progression-free and overall survival (P<0.0001, HR 8.56, 95%CI 2.55-58.7, and P=0.0008, HR 13.3, 95%CI 3.77-47.1, respectively). 10 ACC-P were followed up for at least 6 months: 6 patients tumor-free at last CT scan were negative for Biomarker 1 whereas 3 out of 4 patients with early disease relapse were positive. In two recurrent cases, somatic mutations in ACC driver genes, i.e. MEN1 and ZNRF3, observed at baseline in both tumour and ccfDNA, remained detectable during monitoring. In conclusion, ccfDNA-related biomarkers are frequently detected in patients with primary ACC. They may represent a promising, non-invasive tool to predict early disease progression and complement imaging in disease surveillance. Our findings on ccfDNA-based liquid biopsy will be validated in a larger cohort of ACCs with long-term follow up. Presentation: Saturday, June 11, 2022 12:30 p.m. - 12:45 p.m.