Correlation of levels of cell-free DNA in plasma with imaging -based assessment in Stage III/IV Non-Small Cell Lung Cancer

There are significant limitations to the tools currently used to monitor clinical status and treatment response in late-stage non-small cell lung cancer (NSCLC) patients. Standard-of-care imaging is generally performed every few months, and emerging assays such as tumor mutational burden have yet to be clinically validated. Most of these tools are expensive, further limiting their use. We are exploring a promising new biomarker, high molecular weight cell-free DNA (hmw cfDNA, predominantly longer than 300 bp), which we assay using proprietary ACE (Alternating Current Electrokinetics) technology directly in plasma. In this study, we tested the hypothesis that changes in the level of hmw cfDNA in cancer patients correlate with traditional, imaging-based clinical assessments. We collected longitudinal blood specimens from subjects diagnosed with stage III and stage IV NSCLC and being treated with various therapies (chemo, immuno, targeted) at multiple sites across the US. Specimens were obtained within nine days of routine imaging and were processed to plasma prior to testing. For this analysis, using our hmw cfDNA assay and orthogonal PCR assays, we obtained validated results on samples from 62 subjects which included a total of 117 “deltas”, defined as the difference in hmw cfDNA levels between consecutive blood draws. The correlation between these deltas and clinical assessments, which were made independently by the physician responsible for the subject’s routine care and by a third-party radiologist, was determined. In post-hoc analysis of these results, we found significant correlation between deltas and clinical assessments across classes of therapies, according to receiver operator characteristic (ROC) analysis. This dataset produced an area under the ROC curve (AUROC) of 0.696, with a 95% confidence interval of 0.594 - 0.797. The time intervals between imaging dates varied, due to common practice being followed by physicians, and we found that exclusion of longer time intervals resulted in a progressive improvement in the correlation between hmw cfDNA delta and clinical assessment. Analyzing results with time intervals of less than 120 days, similar to NCCN guidelines, resulted in an AUROC of 0.784 (95% CI of 0.673 - 0.880). Analysis of data from a small subset of subjects (N=11) on immune checkpoint inhibitors resulted in an AUROC > 0.8. These results suggest that hmw cfDNA is a promising biomarker for monitoring treatment response of NSCLC patients, including those on immunotherapy. The ease and lower cost associated with obtaining, processing, and testing samples using this assay would enable it to be employed on a more frequent basis, and it would therefore complement current technologies based on imaging and sequencing. Additional studies to refine the application of this assay and to determine its impact on clinical outcomes will further inform its future use. Citation Format: Robert Kovelman, Patrick F. Desmond, Natalie J. Kennel, Juan P. Hinestrosa, Ellen B. Christie, Delia Ye, Michelle M. Nguyen, Alfred D. Kinana, Mark S. Schechter, David Chu, Chirag M. Shah, Osama Hlalah, John E. Doster, Rajaram Krishnan. Correlation of levels of cell-free DNA in plasma with imaging-based assessment in Stage III/IV Non-Small Cell Lung Cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1350.