Iressa Re-Challenge in Advanced NSCLC EGFR M+ Patients Who Responded to Gefitinib USed as 1st Line or Previous Treatment

Inclusion Criteria at screening (Visit 1) and at Start of Study Treatment (Visit 2): * Provision of informed consent prior to any study specific procedures. * Histologically or cytologically confirmed NSCLC with an activating sensitising EGFR TK mutation as it was determined before starting the first gefitinib treatment by using a well-validated and robust methodology: adenocarcinoma, including Bronchoalveolar Carcinoma (BAC), squamous cell carcinoma, large cell carcinoma, adenosquamous carcinoma or undifferentiated carcinoma or not-otherwise specified NSCLC. * Female or male patients aged 18 years or over with Locally advanced or metastatic stage IIIB/IV disease, not suitable for therapy of curative intent or stage IV (metastatic) disease, eligible for gefitinib re-challenge treatment for NSCLC who have already received gefitinib with a documented complete (CR) or partial response (PR) or stable disease (SD) \>12 weeks as the best response to their 1st gefitinib treatment and progressing during or after a subsequent anti-cancer therapy (excluding EGFR-TKIs) treatment, including but not limited to doublet platinum based chemotherapy or docetaxel monotherapy or pemetrexed monotherapy. * Measurable disease defined as at least one lesion, not previously irradiated, that can be accurately measured at baseline as ≥ 10 mm in the longest diameter (except lymph nodes which must have short axis ≥ 15 mm) with spiral CT or MRI and which is suitable for accurate repeated measurements. * WHO / ECOG / Zubrod performance status 0-2. Exclusion Criteria: * Known severe hypersensitivity to gefitinib or any of the excipients of the product * Prior EGFR TKIs except gefitinib followed by subsequent anti-cancer treatment (including chemotherapy and excluding EGFR-TKIs). Previous adjuvant chemotherapy is allowed. Prior surgery or radiotherapy must be completed more than 6 months before start of study treatment. Palliative radiotherapy must be completed at least 4 weeks before start of study treatment with no persistent radiation toxicity. * Progression disease or stable disease (SD) \<12 weeks as best response to the 1st line treatment with gefitinib * Not progressing during or after the last anti-cancer treatment. * Considered to require radiotherapy to the lung at the time of study entry or in the near future * Past medical history of interstitial lung disease, drug-induced interstitial disease, radiation pneumonitis which required steroid treatment or any evidence of clinically active interstitial lung disease * Pre-existing idiopathic pulmonary fibrosis evidenced by CT scan at baseline * Insufficient lung function as determined by either clinical examination or an arterial oxygen tension (PaO2) of \< 70 Torr * Known or suspected brain metastases or spinal cord compression, unless treated with surgery and/or radiation and stable without steroid treatment for at least 4 weeks prior to the first dose of study medication * Any unresolved chronic toxicity greater than CTC grade 2 from previous anticancer therapy * Concomitant use of known CYP 3A4 inducers such as phenytoin, carbamazepine, rifampicin, barbiturates, or St John's Wort * Pregnancy or breast-feeding * As judged by the investigator, any evidence of severe or uncontrolled systemic disease (eg, unstable or uncompensated respiratory, cardiac, hepatic, or renal disease) * Evidence of any other significant clinical disorder or laboratory finding that makes it undesirable for the patient to participate in the study * Other co-existing malignancies or malignancies diagnosed within the last 5 years with the exception of basal cell carcinoma or cervical cancer in situ * Life expectancy of less than 12 weeks