To investigate the survival benefit of first-line therapy for patients with EGFR-sensitive mutation-positive advanced non-squamous non-small cell lung cancer treated with S-1plus gefitinib versus gefitinib monotherapy

This is a randomized, controlled, open-plan, prospective clinical study. According to the available evidence, we selected patients with locally advanced or metastatic non-squamous non-small cell lung cancer with stage Ⅲ-C-Ⅳ confirmed by cytology or histology and positive EGFR-sensitive mutation, then patients accept first-line treatment with S-1 plus gefitinib or gefitinib. This study will collect FFS during treatment until the patient dies and will follow the survival of the subject after the disease progresses.

Inclusion Criteria:

1. Volunteered for attending the study, and signed informed consent form (ICF)to participate in the study.

2. Males or females aged ≥18 years, < 75 years.

3. Cytologically and Histologically documented, advanced or recurrent (stage IIIc-IV) non-small cell lung cancer patients .

4. exon 19 deletion or exon 21 L858R for EGFR mutation.

5. Patients hadn't received past system treatment, including cytotoxic drugs; For patients who have received adjuvant or neoadjuvant chemotherapy appears recurrence or metastasis more than 6 months from accepting the last dose of chemotherapy drugs

6. Patients must have at least 1 measurable lesion according to the RECIST (version 1.1) criteria.

7. Life expectancy ≥12 weeks.

8. ECOG performance status 0-2.

9. Adequate organ function as defined by the following criteria:

   Absolute neutrophil count (ANC) ≥1.5 x 109/L, and Platelet count ≥100 x 109/L, and Hemoglobin ≥9 g/dL (may be transfused to maintain or exceed this level).

   Total bilirubin ≤ 1.5 x upper limit of normal (ULN), alkaline phosphatase (AP), Aspartate aminotransferase (AST), alanine aminotransferase (ALT) ≤ 2.5 x ULN in the absence of liver metastases or up to 5 ULN in case of liver metastases.

   creatinine clearance≥ 60 ml/min.

10. Fertile men and women must use effective contraception.

11. Subjects are allowed to receive radiation for lesions other than the target lesion, but the end of radiotherapy should be at least 3 weeks apart from randomization;

12. The investigators should judge the subject's compliance to meet the study requirements.

Exclusion Criteria:

1. Histology confirmed for squamous carcinomas, including mixed gland scale cancer, small cell lung cancer.
2. Patients with prior any anti-tumor therapy,including chemotherapy, radiotherapy, immunotherapy or biotherapy
3. Patients with prior exposure to EGFR-TKIs or 5-Fu
4. Not recovered from previous toxic reactions for anticancer treatment (CTCAE grade 1) or not fully recovered from previous surgery
5. Patients who have brain metastasis. It is permitted if the patient has been treated with surgery and/or radiation with evidence of stable disease for at least 4 weeks.
6. Patients haven't been diagnosed other malignant disease, except the basal cell carcinoma and cervical carcinoma.
7. A uncontrolled clinical infection, activity, including acute pneumonia,HIV,HCV. , etc.
8. Sullivudine, brivudine or other antiviral drugs of similar structure were used within 2 months before randomization
9. Patients who have a difficulty in swallowing or drug absorption.
10. Patients with a history of interstitial lung disease or with interstitial lung disease;
11. There are diseases of alimentary canal such as active duodenal ulcer, the ulcerous colitis, intestinal obstruction or other conditions which can cause gastrointestinal bleeding or perforation in the investigator's opinion; or patient has a history of intestinal perforation, intestinal fistula.
12. Evaluation of cardiac function: left ventricular ejection fraction < 50% (echocardiography); Moderate or above disorders of mitral valve and tricuspid shut down;, serious/unstable angina or acute myocardial infarction coronary artery bypass surgery in 6 months before enrollment; patients with class 2 and above cardiac dysfunction according to New York heart association (NYHA) classification
13. Patients with medical history of hemoptysis (defined as about 2.5ml bright blood) 2 weeks before the enrollments
14. Stroke and transient ischemic in 12 months before enrollment.
15. Severe ulcer in the skin wound, trauma and mucosa or fractures have been not fully healed.
16. Patients received CYP3A4 strong inhibitor and/or inducer in 2 weeks before enrollment; Patients received P-gp and breast cancer resistance protein (BCRP) substrates drug in 2 weeks before enrollment.
17. Patients has participated in other clinical trials of antitumor drugs within the previous 28 days, except for those who were able to prove that they were using placebo;
18. Pregnancy or lactating women or pregnant women may be pregnant before pregnancy test positive;
19. Unwillingness to receive contraception by patients or their sexual partners who are fertile but unwilling to receive contraception;
20. The investigators think that there is any clinical or laboratory abnormalities in the subjects that are not suitable for this study.
21. There is a serious psychological or mental abnormalities, researchers assess subjects to participate in this clinical study compliance is insufficient;
22. Allergic reactions to analogs of gefitinib and S-1 and / or Analogs and / or excipients in test drugs.