EGFR-tyrosine kinase inhibitor treatment beyond progression in long-term Caucasian responders to erlotinib in advanced non-small cell lung cancer: a case-control study of overall survival.

INTRODUCTION: Some patients with advanced NSCLC show prolonged disease stabilization on treatment with an EGFR-tyrosine kinase inhibitor (TKI) such as erlotinib. It is not clear how to treat patients who progress after prolonged response to erlotinib. We hypothesized that TKI therapy beyond progression with added chemotherapy, radiotherapy or best supportive care may improve survival. PATIENTS AND METHODS: We retrospectively analyzed all NSCLC patients treated with erlotinib at our institutions since 2004who progressed after at least stable disease on erlotinib for at least 6 months. The first 16 patients did not receive further TKI treatment after progression (controls). The following 25 patients were treated with TKI beyond progression (TKI patients). Overall survival (OS) was analyzed for the whole population, a case-control analysis of pairs matched for gender, smoking status, and histology (n=28), and for patients with known EGFR mutation status (n=23).
RESULTS: Treatment with TKI and chemotherapy was well tolerated. TKI-patients had a significantly longer OS from progression on TKI (case-control: median 14.5 vs. 2.0 months, HR 0.154) and longer OS from diagnosis of lung cancer (case-control: median 54.5 vs. 28.3 months, HR 0.474). An activating EGFR mutation was detected in 13 of the 23 patient tested (57%). Both among patients with and without detection of an activating EGFR mutation, those treated with erlotinib beyond progression had a longer survival.
CONCLUSIONS: In our case-control analysis in long-term erlotinib responders, treatment with TKI beyond progression in addition to chemotherapy or radiotherapy was feasible and lead to prolonged overall survival.