Retrospective Multi-cohort Study of Frontline Afatinib Followed by 2nd Line Therapy Including Osimertinib, Chemotherapy or Other Therapy

This is non-interventional, multi-center, multi-cohort study based on existing data from EGFR sensitizing mutation-positive NSCLC patients treated with afatinib as the first-line treatment. Enrolled patients will be categorized into four cohorts (cohort A, B, C and D) according to the type of second line treatment with biopsy results before start of second line treatment.