Currently, whether adjuvant therapy should be applied to Stage Ib non-small cell lung cancer (NSCLC) patients who received radical resection remains controversial. CALGB9633 studies have shown that for patients with stage Ib NSCLC who received radical resection, postoperative adjuvant chemotherapy does not benefit for all patients, only patients with high risk (cancer diameter >4cm) can benefit. There is still no clear evidence that the postoperative adjuvant chemotherapy or other treatments can improve the survival rate for patients with stage Ib NSCLC.~The EGFR gene mutation rate is about 10% for European patients, and about 30-40% for patients of Asian origins. In a retrospective observation study of 1118 stage I to stage III NSCLC patients who received surgery, D'Angelo et al. found that the risk of death for patients with EGFR sensitive mutation is lower than those without mutation. The authors indicated that postoperative use of TKI for EGFR sensitive mutation patients might be the possible reason. Since the mutation rate of EGRF gene is higher in Asian patients, compared with patients of other origins, the investigators speculate that Asian patients might benefit for postoperative use of TKIs.~EGFR gene mutation detection is routinely prescribed nowadays for lung adenocarcinoma patients who received surgical resection. According to NCCN guideline, stage IB patients with high risk factors are recommended to receive adjuvant chemotherapy. For patients who can not tolerate or decline chemotherapy, non-specific treatment ( Chinese herbal medicine and nonspecific immunomodulators as adjuvant anti-cancer treatment for 2 years) is recommended, otherwise, TKIs（Gefitinib 250 mg daily for 2 years) is also an alternative choice if the cancer has EGFR sensitive mutation. Based on patient's own choice of postoperative adjuvant therapy , the patients were enrolled for observation of prognosis.
Currently, whether adjuvant therapy should be applied to Stage Ib non-small cell lung cancer (NSCLC) patients who received radical resection remains controversial. There is still no clear evidence that the postoperative adjuvant chemotherapy or other treatments can improve the survival rate for patients with stage Ib NSCLC. Tyrosine Kinase Inhibitors (TKIs) such as Gefitinib and Erlotinib are widely accepted as the first-line therapy for Epidermal growth factor receptor (EGFR) gene mutation late stage NSCLC patients. However the effect is largely uncertain for early stage patients who received surgery. The investigators aim to evaluate the effect of postoperative adjuvant use of Gefitinib for high risk stage Ib EGFR sensitive mutation NSCLC patients.