- 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.