Crizotinib, an inhibitor of anaplastic lymphoma kinase (ALK), was approved by Food and Drug Administration (FDA) for the treatment of patients with ALK-positive non-small cell lung cancer (NSCLC) and its administration has achieved considerable success. However, adverse effects inevitably occurred and the most common one was hepatic toxicity, appearing as elevating alanine aminotransferase(ALT) and aspartate aminotransferase(AST). Therefore, the investigators try to figure out the mechanism of crizotinib-inducing hepatic toxicity, and explore whether there is any biological marker to diagnose this side effect in an early stage, which may realize individualized therapy with more efficacy and less side effects.

Inclusion Criteria:

1. patients who were histologically and cytologically confirmed NSCLC at stage III or IV
2. harbored ALK fusion gene and took crizotinib
3. age:18~75years
4. Eastern cooperative oncology group performance status(ECOG PS): 0~2 points
5. the expected lifetime is more than 12 weeks after being recruited

Exclusion Criteria:

1. patients who also suffered from other malignant tumor
2. uncontrolled systemic diseases,central nervous system (CNS) metastasis
3. clinically active interstitial lung diseases
4. severe liver dysfunction caused by hepatic cirrhosis or hepatitis （Child-Pugh class C, total index score 10-15 points）
5. taking drugs that interact with crizotinib

Patients who were diagnosed with stage III or IV non-small cell lung cancer (NSCLC), harbored ALK fusion gene and took crizotinib.