Abstract
PURPOSE: Circulating tumor DNA (ctDNA) holds promise as an early endpoint to predict overall survival (OS). The creation and structured interrogation of aggregated datasets inform the hypothesis that ctDNA is reasonably likely to predict treatment benefit. Friends of Cancer Research convened a diverse working group to establish and implement an analysis plan assessing patient-level associations between changes in ctDNA levels with OS and progression-free survival (PFS). EXPERIMENTAL DESIGN: The aggregate dataset included eight clinical trials representing 940 patients with biomarker-positive advanced non-small cell lung cancer treated with tyrosine kinase inhibitors. Detection of baseline and on-treatment ctDNA was assessed for associations with OS and PFS. Additionally, combinations of ctDNA detection and RECIST measurements up to 10 weeks on treatment were considered. RESULTS: Patients with detected ctDNA at baseline that became nondetected on treatment ("clearance") experienced improved OS compared with patients with persistently detected ctDNA (adjusted HR = 2.12, P < 0.001). This pattern was also seen in the subset of patients with stable disease as measured by RECIST within 10 weeks of treatment initiation (adjusted HR = 4.15, P < 0.001). Results were similar for PFS. CONCLUSIONS: In patients with oncogene-driven advanced non-small cell lung cancer treated with tyrosine kinase inhibitors, ctDNA clearance within 10 weeks of treatment initiation was associated with improved OS and PFS. These patient-level results support the growing evidence that demonstrates a change in ctDNA levels during treatment is associated with clinical benefit. Future prospective trials should include predefined thresholds of molecular response to advance the utility of ctDNA as an early endpoint.