A Study of PC Sequential Pemetrexed Single Drug Maintenance Treatment for NSCLC and Related Predictive Biomarkers

Inclusion Criteria: .≥65 years or PS 2 * Patients who were diagnosed by the histologic, cytologic diagnosis of IV non-small cell lung cancer * Patients received no chemical therapy or only received targeted therapy,and there is evidence show the patent is PD * Presence of at least one index lesion measurable by CT scan or MRI * leucocyte ≥ 3.5×109/L * neutrophil ≥ 1.5×109/L * platelet ≥ 80×109/L * Hemoglobin ≥ 9g/L * ALT and AST ≤ 2.5×ULN ,Tbil≤ 1.5×ULN * BUN≤ 1.5×ULN * Signed written informed consent Exclusion Criteria: * squamous carcinoma or small cell lung cancer * Patients were allergic to pemetrexed * Patients received chemotherapy before * Uncontrolled acute infection .Uncontrolled pleural effusion * Severe symptomatic heart disease * Severe infection or metabolic disfunction * Patients with other malignant tumor * Uncontrolled brain metastases * Patients have accepted other clinical trials * Female patients during their pregnant and lactation period, or patients without contraception * Mental disorientation of disorder * Glucocorticoids taboo