Is there a difference in PFS or OS of T790M-mutated NSCLC patients treated with osimertinib either after chemotherapy or immediately after previous target therapy?

Background: Osimertinib (Tagresso) is recommended as an option for treating patients with locally advanced or metastatic EGFR T790M mutation-positive NSCLC whose disease has progressed after first-line TKIs. We compared OS and PFS in patients who received osimertinib treatment immediately after previous treatment with TKIs, and those who received osimertinib after their last cycle of chemotherapy. Methods: This study enrolled a total of 2605 patients who were diagnosed with lung cancer between January 2013 and April 2017. Among these patients, there were 779 patients with inoperable EGFR-mutated NSCLC who had received TKIs as first-line therapy. Furthermore, 166 of these 779 patients who were resistant to TKIs had received re-biopsy. There were 71 patients who received osimertinib therapy for at least 2 weeks since March 2016. Results: Demographics and clinical characteristics of the 71 patients are described in the table. Among these cases, 26 (36.6%) patients received osimertinib as 2nd-line therapy after first-line TKI therapy. Seventeen (23.9%) patients received osimertinib as 3rd-line therapy, and 28 (39.4%) patients received osimertinib in > = 4th-line setting. The median PFS in patients as 2nd-line therapy was 11.9 months and that was 17.3 months as 3rd-line therapy. The median PFS in patients as > = 4th-line therapy was 9.3 months. Among the 71 patients, there were 34 (47.9%) patients who received it after previous chemotherapy (Group A), and 37 patients (52.1%) who received osimertinib immediately after previous TKI therapy (Group B). The median PFS for Group A and Group B patients was 12.8 months and 11.0 months, respectively (p = 0.306). A higher percentage of patients in Group B had progressive disease (8 cases, 21.6%) compared to Group A (2 case, 5.9% ; χ2 = 0.08). Besides, obesity patients (BMI > = 27) had trend of shorter PFS with osimertinib therapy. (8.4 months vs. 12.6 months, P = 0.05). Conclusions: Our data suggested that T790M-mutated NSCLC patients may have a better response, and longer PFS when treated with osimertinib therapy after previous chemotherapy compared to after previous TKI treatment. Due to the small sample size, our data need to be updated and need further re-analysis. Legal entity responsible for the study: Chien-Hao Lai; Chin-Chou Wang. Funding: Has not received any funding. Disclosure: All authors have declared no conflicts of interest.