Efficiency of Icotinib in Plasma ctDNA EGFR Mutation-positive Patients Diagnosed With Lung Cancer

Inclusion Criteria:

* Clinical diagnosis of peripheral lung cancer, but the pathological diagnosis is not yet clear.
* Plasma EGFR mutations (EGFR 19del and/or 21L858R) positive (simultaneously detected by Super-ARMS, ddPCR and NGS，any positive).
* unavailable of radical surgery or radical radiotherapy.
* not previously received anticancer therapy like surgery, chemotherapy, radiation therapy, and biotherapy etc.
* Palliative radiotherapy for bone metastases is permitted, but there is no continuous toxicity associated with radiation therapy.
* Age 18-75 years old with performance status of 0 to 3.
* With a measurable disease(longest diameters \>=10mm with Spiral computed tomography (CT)) according to RECIST Criteria.None of the lesions treated with radiotherapy could be used as target lesions.
* Adequate hematological, biochemical and organ functions.

Exclusion Criteria:

* Severe systemic disease out of control such as unstable or uncompensated respiratory,cardiac,liver,renal diseases.
* Evidence of interstitial lung diseases
* Evidence of any other significant clinical disorder or laboratory finding that makes it undesirable for the subject to participate in the study
* Other situations researchers think not appropriate to enter the group