The purpose of this study is to assess the overall response rate to Iressa as a first-line treatment in chemonaive patients with inoperable Non-Small Cell Lung Cancer (NSCLC)

The epidermal growth factor receptor (EGFR) is a promising target for anticancer therapy because it is expressed or highly expressed in a variety of tumors, including NSCLC.Furthermore, high levels of EGFR expression have been associated with a poor prognosis in lung cancer patients in several studies. EGFR-targeted cancer therapies are currently being developed; strategies include inhibition of the intracellular tyrosine kinase domain of the receptor by small molecules such as gefitinib (Iressa [ZD1839]; AstraZeneca, Wilmington, DE). Iressa is an orally active, selective EGFR tyrosine kinase inhibitor that blocks signal transduction pathways implicated in the proliferation and survival of cancer cells.

Inclusion Criteria:

• Histologically or cytologically confirmed stage IIIB/IV NSCLC
• No immediate need for palliative radiotherapy and No prior chemotherapy
• age > 20 Y/O
• ECOG PS: 0 - 2
• ANC >2000
• PLT >100k
• Hb > 10
• total bilirubin < 2.0 mg/dL
• serum creatinine < 2 mg/dl
• SGPT and SGOT < 2.5 ×ULN, alkaline phosphatase < 5 ×ULN
• life expectancy >6mos.

Exclusion Criteria:

• If the patients have brain metastases or receive radiotherapy, the disease must be stable for more than 6 weeks after the last dose of radiotherapy
• 2nd malignancies
• Unable to swallow tablets
• Patients (M/F) with reproductive potential not implementing adequate contraceptive measurements
• Pregnant or lactating patients
• Participation in other clinical trials within 30 days of study entry
• Major systemic disease which in the investigator's opinion might confound the clinical trial