After inductive TKI therapy in NSCLC with sensitizing EGFR mutations, the residual lesion might be the source of subsequent disease progression, defined as acquired resistance to TKI. Two reasons can be used to explain the formation of the residual lesion：1）there is a subgroup of cancer cells that are not sensitive to TKI therapy because of tumor heterogeneity, like de novo T790M mutation; 2)some cancer cells can keep static state during the beginning treatment, and then develops acquired resistance to TKI therapy under the long-term drug pressure and continue to re-proliferation. From this point of view, elimination of residual lesion provides the chance to reduce or slow the possibility of developing resistance to TKI.