Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors Beyond Progressive Disease: A Retrospective Analysis for Japanese Patients with Activating EGFR Mutations

Introduction: It is not determined whether the continuous use of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) is reasonable for patients with activating EGFR mutations, who have progressed with the drug. Methods: We retrospectively analyzed the data from 2002 to 2010 of consecutive patients who had advanced non–small-cell lung cancer (NSCLC) harboring activating EGFR mutations and showed radiological disease progression after EGFR-TKI treatment as the first-line or second-line setting. We classified them into two groups: continuous EGFR-TKI and switching to chemotherapy, and compared the clinical outcomes. Multivariate analysis for survival was performed including age, sex, Eastern Cooperative Oncology Group performance status (0–1/ 2–4), brain metastasis, EGFR mutations (deletions in exon 19 versus L858R), continuous EGFR-TKI (yes/no), and initiation of EGFR-TKI (first versus second). Results: A total of 551 NSCLC patients were screened for EGFR mutations in the period, and 186 patients had activating EGFR mutations. To explore the potential use of EGFR-TKI beyond progressive disease (PD), 64 patients were selected and analyzed. There were 13 men and 51 women, and median age was 65.5 years (range, 42–86). Among them, 31 patients had deletions in exon 19, and 33 had point mutation of L858R in exon 21. Thirty-nine patients were continuing EGFR-TKI beyond PD; 25 patients were switched to cytotoxic chemotherapy alone. The median overall survival was 32.2 months in the patients continuing EGFR-TKI, and 23.0 months in the patients switching to chemotherapy, presenting a significant difference between the two groups (p = 0.005). Cox analysis showed that continuous EGFR-TKI after PD (hazards ratio 0.42, 95% confidence interval: 0.21–0.83, p = 0.013) was associated with improved survival. Conclusion: Continuous use of EGFR-TKI beyond PD may prolong overall survival compared with switching to cytotoxic chemotherapy in patients with activating EGFR mutations. A prospective study will be needed to confirm our results.