Abstract 3411: Detection and monitoring of tumor-derived mutations in ctDNA using the UltraSEEK Lung Panel on the MassARRAY System in metastatic NSCLC patients
Authors: van der Leest Paul , Janning Melanie , Rifaela Naomi , Azpurua Maria L. Aguirre , Kropidlowski Jolanthe , Loges Sonja , Lozano Nicholas , Sartori Alexander , Irwin Darryl , Lamy Pierre-Jean , Hiltermann T. Jeroen N. , Groen Harry J. , Pantel Klaus , van Kempen Léon C. , Wikman Harriet , Schuuring Ed 
Published: June 2022

Abstract
Background: The analysis of circulating tumor DNA (ctDNA) is a potential minimally invasive molecular tool to guide treatment decision making and disease monitoring. A suitable diagnostic-grade platform is required for detection of tumor-specific mutations with high sensitivity in circulating cell-free DNA (ccfDNA) of cancer patients.
Methods: In an international multicenter study conducted by three laboratories participating in the CANCER-ID consortium, a cohort containing 177 cell-free plasma samples at baseline, follow-up or disease progression derived from 72 patients treated for advanced-stage non-small cell lung cancer (NSCLC), relevant mutations were tested using the UltraSEEK® Lung Panel on the MassARRAY® System covering 73 hotspot mutations in EGFR, KRAS, BRAF, ERBB2 and PIK3CA, and compared against mutation-specific droplet digital PCR (ddPCR) and tumor tissue next-generation sequencing (NGS) performed in routine diagnostics. Variant detection accuracy at primary diagnosis and during disease progression, and ctDNA dynamics as a marker of treatment efficacy were analyzed.
Results: The UltraSEEK® Lung Panel revealed an overall detection rate of 87.2% irrespective of ccfDNA input, and a specificity of &gt;99.5% using the reference material. When comparing the 131 variants identified in the patient-derived cell-free plasma using UltraSEEK® with mutation-specific ddPCR analyses, a concordance of 90% was found. The 77 diagnostically or clinically relevant variants identified in 66 pretreatment tumor tissue showed an overall concordance with UltraSEEK® of 73% at baseline with a false-negative rate of 3%. When restricting to therapeutically targetable mutations, the concordance elevated to 85%. A decrease in ctDNA levels at 4-6 weeks after start of treatment detected with UltraSEEK® correlated with a prolonged median PFS (46 vs 11 weeks; P&lt;0.05) and OS (145 vs 39 weeks; P&lt;0.001). In four out of thirteen NSCLC patients treated with targeted therapy, resistance mutations were identified using UltraSEEK® at disease progression, implicating the requirement of a therapy switch.
Conclusion: Using plasma-derived ccfDNA, the UltraSEEK® Lung Panel with a mid-density set of the most common predictive markers for NSCLC is an alternative tool to detect both mutations at diagnosis and disease progression, and to monitor treatment response.
Citation Format: Paul van der Leest, Melanie Janning, Naomi Rifaela, Maria L. Aguirre Azpurua, Jolanthe Kropidlowski, Sonja Loges, Nicholas Lozano, Alexander Sartori, Darryl Irwin, Pierre-Jean Lamy, T. Jeroen N. Hiltermann, Harry J. Groen, Klaus Pantel, Léon C. van Kempen, Harriet Wikman, Ed Schuuring. Detection and monitoring of tumor-derived mutations in ctDNA using the UltraSEEK Lung Panel on the MassARRAY System in metastatic NSCLC patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3411.