ASPET Study: An Observational Study of Tarceva (Erlotinib) in First Line in Patients With Advanced Non-Small Cell Lung Cancer Harbouring EGFR Activating Mutations

Inclusion Criteria: * Adult patients, \>/= 18 years of age * Histologically or cytologically confirmed locally advanced or metastatic (IIIB/IV) non-squamous non-small cell lung cancer (NSCLC) which is routinely evaluated in clinical practice according to RECIST criteria * EGFR mutation-positive disease according to local laboratory testing * Patients on treatment with Tarceva monotherapy as first-line treatment according to the physician's usual practice Exclusion Criteria: * Prior systemic therapy for advanced NSCLC. The administration of neoadjuvant or adjuvant chemotherapy is allowed as long as it was finalized \>6 months prior to receiving Tarceva * Participation in another clinical study * Patients could have received radiotherapy as long as the irradiated lesion was not the only lesion for evaluating response and a long as the radiotherapy was completed before initiating Tarceva treatment