Circulating Tumor Cell-Free DNA as Prognostic Biomarker in Non-Small Cell Lung Cancer Patients Undergoing Immunotherapy: The CORELAB Experience

Abstract

The expression level of Programmed Death-Ligand 1 (PD-L1) determined by the immunohistochemical method is currently approved to test the potential efficacy of immune-checkpoint inhibitors and to candidate patients with Non-Small Cell Lung Cancer (NSCLC) for treatment with immunotherapeutic drugs. As part of the CORELAB (New prediCtivebiOmaRkers of activity and Efficacy of immune checkpoint inhibitors in advanced non-small cell Lung cArcinoma) project, aimed at identifying new predictive and prognostic biomarkers in NSCLC patients receiving immunotherapeutic drugs, we investigated the role of circulating tumor DNA (ctDNA) molecular characterization as an additional predictive biomarker. We analyzed plasma ctDNA by targeted Next Generation Sequencing in a subset of 50 patients at different time points. ctDNA content was inversely correlated with the clinical outcome both at a baseline and after 2 months of treatment. OS was significantly higher in patients with ≥50% ctDNA reduction. TP53 and KRAS were the most frequently mutated genes, and patients with KRAS and/or TP53 mutations showed worse outcomes than patients without detectable variants or with mutations in other genes. Fewer common variants were found in BRAF, EGFR, MAP2K1, MET, NRAS, and PIK3CA genes. Our data demonstrated that molecular characterization of ctDNA and also its quantitative evaluation could serve as a dynamic, real-time prognostic, and predictive biomarker, enabling regular molecular monitoring of therapy efficacy in support of other medical examinations.

Keywords: NGS; NSCLC; PD-L1; immunotherapy; liquid biopsy; prognostic biomarkers.

Figure 1

ctDNA and radiological variation between T0 (untextured) and T1(textured); patients without detectable variants at both times are not represented. Patients 1–14 had a reduction in ctDNA, patients 15–19 had stable ctDNA, and patients 20–24 had an increase in ctDNA. Bars are represented in green for patients with radiological Stable Disease (SD) per RECIST, blue for Partial Response (PR), and red for Progressive Disease (PD).

Figure 2

Distribution of ctDNA values at baseline and after 2 months of therapy based on radiological response. Distribution of ctDNA levels at T0 (A), after two months of immunotherapy, T1 (B) and the variation of ctDNA amount between the two time points ∆ctDNA (ctDNAT1 − ctDNAT0)/ctDNAT0; (C), according to the radiologic response; (Mann–Whitney test).

Figure 3

Association of molecular response with survival outcomes (A); association of the pre-treatment genomic status with survival outcomes (B).

Figure 4

Longitudinal monitoring of an NSCLC patient with a TP53 mutation. ctDNA longitudinal monitoring of a case study patient at T0 (day 0), T1 (day 54), T2 (day 112) and at TP (day 184). ctDNA VAF% (corresponding to a TP53 variant) at different follow-ups are shown with associated clinical data.