Delay of chemotherapy through use of post-progression erlotinib in patients with EGFR-mutant lung cancer.

7547 Background: 1 st -line tyrosine kinase inhibitor (TKI) therapy for patients (pts) with EGFR-mutant lung cancer prolongs progression free survival (PFS) and improves quality of life. When pts develop acquired resistance to TKI, chemotherapy is the only approved systemic treatment. Anecdotal evidence suggests that change of therapy can be delayed in some pts through continued TKI beyond progression (PD), but the effectiveness of this approach has not been quantified. Methods: Through an IRB-approved mechanism, pts with advanced lung cancer and EGFR sensitizing mutations treated on 3 prospective trials of 1 st -line erlotinib were identified. Only pts with RECIST PD while on erlotinib were studied. Time from PD until use of an alternate systemic therapy (or death) and characteristics at PD (development of new extra-thoracic metastases or cancer-related symptoms) were assessed. Results: 42 eligible pts were identified with the following characteristics: median age 70, 86% female, 93% non-Asian, 50% never-smokers, 83% adenocarcinoma, 100% EGFR-mutant (55% exon 19, 36% exon 21, 9% exon 18). Median PFS on erlotinib was 13 months. After PD, alternate systemic therapy was delayed >3 months in 19 pts (45%; 95%CI: 31%-60%), through a combination of post-PD erlotinib (16 pts), radiation (6 pts), and/or surgery (3 pts), or on observation alone (2 pts). These 19 pts commonly had exon 19 deletions and were more likely to have no cancer-related symptoms at PD (Table), and had a median post-PD survival of 29 months. Alternate systemic therapy was delayed >12 months in 8 pts (19%). Conclusions: In a subset of pts with EGFR-mutant lung cancer and acquired resistance to TKI, chemotherapy can be delayed with the aid of post-PD TKI and local treatment modalities. This indolent PD is likely due to ongoing tumor EGFR dependence. In pts who are tolerating TKI and have asymptomatic progression, we recommend this palliative treatment strategy as an option for delaying chemotherapy and maximizing quality of life. Table: see text