Analysis of circulating tumor DNA in localized lung cancer for detection of molecular residual disease and personalization of adjuvant strategies.

Abstract

8519 Background: Identifying localized non-small cell lung cancer (NSCLC) patients with residual disease following curative intent therapy is difficult due to normal tissue changes caused by surgery or radiation and an inability to detect microscopic disease. Analysis of circulating tumor DNA (ctDNA) might enable identification of molecular residual disease (MRD) and personalization of adjuvant treatment approaches but has not been explored in lung cancer. Methods: We applied CAPP-Seq, an ultra-sensitive next-generation sequencing based ctDNA quantitation method, to pre- and post-treatment blood samples from a cohort of 41 patients treated with chemoradiation, radiotherapy or surgery for stage I-III primary lung cancer. Detection of ctDNA at a single MRD time-point within 4 months of treatment completion was compared with surveillance by cross-sectional imaging. Furthermore, we developed an approach for identification of tumor mutation burden based on mutations detected in plasma, leveraging whole exome sequencing data from 1,177 NSCLCs sequenced by TCGA. Results: Median follow-up time was 35 months. Pre-treatment ctDNA was detected in 38 (93%) patients and 19 (46%) had detectable post-treatment ctDNA MRD. MRD+ patients displayed significantly inferior 3-year freedom from progression (0% vs. 92%; HR 38; P < 0.0001) and 3-year overall survival (8% vs. 75%; HR 12; P < 0.0001) than MRD- patients. Detection of ctDNA MRD had positive and negative predictive values for disease progression of 100% and 93%, respectively. Furthermore, we non-invasively identified activating EGFR mutations or high mutational burden (≥5 CAPP-Seq non-synonymous mutations, corresponding to > 200 non-synonymous mutations per exome or > 4 single nucleotide variants per megabase of exome) in 47% of patients with detectable ctDNA MRD, suggesting potentially favorable responses to TKIs and immune checkpoint inhibitors, respectively. Conclusions: Our results indicate that ctDNA analysis accurately detects MRD in localized lung cancer patients and could facilitate personalized adjuvant treatment at early time-points when disease burden is minimal.