Long term efficacy of first-line afatinib and the clinical utility of ctDNA monitoring in patients with suspected or confirmed EGFR mutant non-small cell lung cancer who were unsuitable for chemotherapy.

Abstract

Background: Here we present long-term outcomes of first line afatinib in comorbid patients with suspected or confirmed EGFR mutant NSCLC otherwise considered unsuitable for chemotherapy, and the clinical utility of serial ctDNA monitoring.

Methods: TIMELY (NCT01415011) was a multicentre, single arm, phase II trial conducted in the UK. Patients aged ≥18 were treated with daily oral afatinib (40 mg) until disease progression or unacceptable toxicity. Blood samples for ctDNA analysis were obtained at baseline and 12-weekly until treatment discontinuation. The primary endpoint was PFS.

Results: Thirty-nine patients were enrolled between March 2013 and August 2015. Median follow-up was 98 months (range 69-101). Median PFS was 7.9 months (95% CI 4.6-10.5). Seven patients (18%) continued afatinib beyond 18 months, 3 beyond 36 months and 2 were still on treatment at last follow-up 101 months post-treatment initiation. Analysis of baseline ctDNA samples identified 8 EGFR mutant cases that were not identified by tissue genotyping and ctDNA clearance was associated with improved PFS and OS.

Conclusion: Afatinib is a viable treatment option for tissue or ctDNA-detected EGFR mutant NSCLC comorbid patients, with a proportion achieving long-term clinical benefit. Plasma ctDNA testing improved EGFR mutant identification and its clearance predicted improved PFS and OS.