It has been more than 3 years since crizotinib was introduced into China for clinical trials in February 2011, and more than 50 patients have been tested positive for ALK and given access to crizotinib treatment in the Department of Lung Oncology at 307 Hospital, with an efficiency rate of 76.8% and a disease control rate of 93.2%. Many patients had significant tumor shrinkage, and one patient has been on the drug for 3 years and 3 months to date (see figure). However, despite the remarkable efficacy of crizotinib, treatment failure (or drug resistance) is still an inevitable challenge. LDK378, an irreversible ALK inhibitor, has been shown to have significant efficacy in patients with crizotinib resistance, and is an excellent choice for patients who have failed crizotinib treatment. Currently, a clinical trial of LDK378 in ALK-positive non-small cell lung cancer patients who have failed crizotinib is underway in our department. The study mainly includes ALK-positive lung cancer patients who have failed crizotinib treatment and are given LDK378 monotherapy to observe its safety and efficiency.