Assess the Efficacy, Safety and Tolerability of Gefitinib (Iressa® 250mg) as Maintenance Therapy in Locally Advanced or Metastatic (Stage IIIB/IV) Non Small Cell Lung Cancer (NSCLC)

A Placebo-Controlled, Multicentre, Randomised, Parallel Group, Trial to Assess the Efficacy, Safety and Tolerability of Gefitinib (Iressa® 250mg) as Maintenance Therapy in Locally Advanced or Metastatic (StageIIIB/IV) Non Small Cell Lung Cancer (NSCLC) Chinese Patients Who HaveNot Experienced Disease Progression or Unacceptable Toxicity During Front Line Standard Platinum-Based Chemotherapy