Biomarker subset analysis of a phase IIIb, open-label study of afatinib in EGFR tyrosine kinase inhibitor-naive patients with EGFRm plus non-small-cell lung cancer

Aim: To explore the relationship between mutations in cfDNA and response to afatinib. Patients & methods: In total, 64 patients from one Chinese site with locally advanced/metastatic EGFRm+ non-small-cell lung cancer, who received afatinib 40 mg once daily, were included. Results: Overall, 33 (82.5%) patients became EGFRm- by visit 3; median progression-free survival was longer in these patients vs those who did not (11.0 vs 5.5 months). Progression-free survival was shorter in 42 (45.2%) patients with non-EGFR co-mutations at baseline vs those without (8.1 vs 12.5 months). Neither difference was significant. Conclusion: Afatinib provided clinical benefit for patients with EGFRm+ non-small-cell lung cancer across all subgroups. EGFRm status assessment in plasma cfDNA is a useful method of monitoring treatment. Plain language summary: We conducted a study in 64 Chinese patients with non-small-cell lung cancer to investigate the relationship between cancer mutations detected in the blood and the response to treatment with afatinib, which is known to be effective against EGFR mutations. Technology is now available to detect these mutations in the blood, as an alternative to obtaining and testing lung tissue samples. All 64 patients had EGFR mutations (and some patients had additional types of mutations) when afatinib was started (visit 1 in the study). By visit 3, most patients (82.5%) no longer had EGFR mutations detected in their blood, and these patients responded better to afatinib than those who still had EGFR mutations in their blood. Patients with additional types of mutations generally did not respond as well as those who had only EGFR mutations. Although results showed clinical benefit with afatinib using assessment of mutation status in the blood, statistical significance could not be shown due to the small size of the study.