Phase II Study of Erlotinib for Acquired Resistance to Gefitinib in Patients with Advanced Non-small Cell Lung Cancer

Background: Gefitinib and erlotinib are used to treat advanced non-small cell lung cancer (NSCLC). Gefitinib is a common first-line treatment, but most patients develop resistance. This phase II study evaluated the efficacy of erlotinib after acquired resistance to gefitinib. Patients and Methods: Between January 2008 and September 2009, we enrolled 50 patients with advanced NSCLC who had received one or more chemotherapy regimens, including gefitinib monotherapy to which they had partial responses (PR) or stable disease (SD). Erlotinib (150 mg) was administered until disease progression or unacceptable toxicity. Patients were 11 males, 39 females; median age 65 years (range=36-81 years); 46 with adenocarcinoma; performance status 01112: 2411917; and smoking status, never/former/current: 33/15/2. Prior gefitinib response, PR/SD: 36/14. Median duration of prior gefitinib therapy was 419 days (range=63-1,540 days). Median interval after gefitinib therapy was 29 days (range-13-1,198 days). Results: Of 47 patients on erlotinib, four showed PR and 29 showed SD [response rate, 8.5%; disease control rate (DCR), 70.2%]. DCR for patients who continued gefitinib treatment for more than one year was significantly higher (81.5%) than for patients who could not continue (57.1%; p=0.018); but was not affected by prior gefitinib response or treatment interval. Median tiMETo treatment failure: 100 days (95% confidence interval=90-110 days); median overall survival: 342 days (95% confidence interval=242-442 days). Rash (78%) and diarrhea (68%) were the most common adverse reactions; grade 5 pneumonitis occurred in one patient (2%). Conclusion: Erlotinib treatment after gefitinib failure may prolong the efficacy of epidermal growth factor receptor tyrosine kinase inhibitors treatment.