Mixed response to osimertinib and the beneficial effects of additional local therapy.

An MR was detected in 15% of NSCLC patients with T790M. This finding suggests that several different resistance mechanisms are active within a single patient who develops resistance to EGFR-TKIs. Osimertinib is basically effective for tumors that acquire resistance to EGFR-TKIs as a result of T790M mutation. Therefore, additional local therapy may be beneficial for patients who develop an MR to osimertinib.