Circulating tumor DNA (ctDNA) molecular residual disease (MRD) following curative-intent treatment strongly predicts recurrence in multiple tumor types, but whether further treatment can improve outcomes in patients with MRD is unclear. We applied cancer personalized profiling by deep sequencing (CAPP-Seq) ctDNA analysis to 218 samples from 65 patients receiving chemoradiation therapy for locally advanced non-small-cell lung cancer, including 28 patients receiving consolidation immune checkpoint inhibition (ICI). Patients with undetectable ctDNA after chemoradiation therapy had excellent outcomes whether or not they received consolidation ICI. Among such patients, one died from consolidation ICI-related pneumonitis, highlighting the potential utility of only treating patients with MRD. In contrast, patients with MRD after chemoradiation therapy who received consolidation ICI had significantly better outcomes than patients who did not receive consolidation ICI. Furthermore, the ctDNA response pattern early during consolidation ICI identified patients responding to consolidation therapy. Our results suggest that consolidation ICI improves outcomes for non-small-cell lung cancer patients with MRD and that ctDNA analysis may facilitate personalization of consolidation therapy.

Circulating tumor DNA (ctDNA) minimal residual disease (MRD) is a powerful biomarker with the potential to improve survival outcomes for non–small-cell lung cancer (NSCLC). Multiple groups have shown the ability to detect MRD following curative-intent NSCLC treatment using next-generation sequencing–based assays of plasma cell-free DNA. These studies have been modest in size, largely retrospective, and without thorough prospective clinical validation. Still, when restricting measurement to the first post-treatment timepoint to assess the clinical performance of ctDNA MRD detection, they have demonstrated sensitivity for predicting disease relapse ranging between 36% and 100%, and specificity ranging between 71% and 100%. When considering all post-treatment follow-up timepoints (surveillance), including those beyond the initial post-treatment measurement, these assays' performances improve with sensitivity and specificity for identifying relapse ranging from 82% to 100% and 70% to 100%, respectively. In this manuscript, we review the evidence available to date regarding ctDNA MRD detection in patients with NSCLC undergoing curative-intent treatment and the ongoing prospective studies involving ctDNA MRD detection in this patient population.