LAUSR

PURPOSE Next to secondary epidermal growth factor receptor (EGFR) mutations, cMET amplification plays an important role in mediating acquired resistance to EGFR tyrosine kinase inhibitors (TKI) treatment. Crizotinib, a dual ALK and cMET inhibitor, can induce responses in patients with EGFR mutation positive non-small cell lung cancer (NSCLC) that acquire cMET amplification after EGFR TKI treatment. However, little is known about the duration of response and post-progression resistance mechanisms. Here, we report on the clinical outcome of a series of patients with cMET-driven resistance to EGFR TKIs, treated with crizotinib. MATERIALS AND METHODS Eight patients with EGFR mutation positive NSCLC that acquired cMET amplification after EGFR TKI treatment were treated with crizotinib 250 mg twice daily, as monotherapy (n = 2) or in combination with an EGFR TKI (n = 6). RESULTS Four out of eight patients (50%) showed a partial response (PR) according to RECIST 1.1. Median progression-free survival (PFS) was 1.4 (95% CI 1.2-5.0) months. Responses were short-lasting with a median PFS of 3.5 (95% CI 1.4-5.2) months in patients with a PR. Median overall survival was 5.9 (95% CI 1.3-6.0) months and not statistically different between responders and non-responders (p = 0.37). All but one patient tolerated crizotinib treatment well. Heterogeneous responses were seen in patients with progressive disease as best response with a marked size decrease of the biopsied (cMET amplification positive) lesion and progression of other lesions. cMET amplification was not always mutually exclusive with other EGFR TKI resistance mechanisms. Post-progression biopsies were negative for cMET amplification. CONCLUSION Crizotinib treatment for patients with EGFR mutation positive NSCLC that acquire cMET amplification after EGFR TKI treatment results in short-lived and often heterogeneous responses, possibly due to subclonality of cMET-driven resistance and co-occurrence of other EGFR TKI resistance mechanisms.