Prospective Assessment of Continuation of Erlotinib or Gefitinib in Patients with Acquired Resistance to Erlotinib or Gefitinib Followed by the Addition of Pemetrexed

Introduction: Patients with epidermal growth factor receptor (EGFR) mutation positive non-small-cell lung cancer exhibited marked response to gefitinib or erlotinib. In most cases, however, the patients showed disease progression after EGFR-tyrosine kinase inhibitor (TKI) treatment. We evaluated the efficacy and safety of pemetrexed in combination with EGFR-TKI in patients with disease progression. Methods: Patients with EGFR-mutant stage IIIB or IV non-small-cell lung cancer that progressed during gefitinib or erlotinib therapy were administered pemetrexed with the continuation of EGFR-TKI treatment. Pemetrexed was administered on day 1 at a dose of 500 mg/m(2), and EGFR-TKI was sequentially administered on days 2 to 16. This treatment was repeated every 3 weeks until disease progression. The primary endpoint was disease control rate. Results: Twenty-seven patients were enrolled in this study. The median number of treatment cycles was six. Overall response rate was 25.9% (95% confidence interval, 9.4%-42.4%) and disease control rate was 77.8% (95% confidence interval, 62.1%-93.5%). Grade 3/4 hematological toxicities were neutropenia (22.2%), leukopenia (14.8%), and anemia (7.4%). Grade 4 nonhematological toxicities were not observed. Major grade 3 nonhematological toxicities were anorexia (14.8%), infection (14.8%), and fatigue (11.1%). The median progression-free survival was 7.0 months, and median survival time was 11.4 months. No treatment-related deaths occurred. Conclusions: Pemetrexed in combination with erlotinib or gefitinib after disease progression shows favorable response and acceptable toxicity.