Introduction: A mutation in the gene encoding the epidermal growth factor (EGFR) occurs in 12% of lung adenocarcinoma. They are sensitive to EGFR blockade with specific tyrosine kinase inhibitors (TKIs). Transformation in small cell lung cancer (SCLC) is a mechanism of resistance to TKIs, which occurs in 3-4% of patients. In the current study, we describe the characteristics and survival data of SCLC arising from NSCLC. Methods: We performed a multicentric retrospective collection of cases from 2005 to 2015 including patients of 27 centers in France and Italy with stage III or IV NSCLC and a secondary transformation to SCLC with histological proof. Results: Forty seven cases of SCLC transformation were registered, 34 in EGFR mutant NSCLC and 13 in the non EGFR mutant NSCLC. The median age was 62 [interquartile 25-75%, 56-70] years. In the EGFR mutant, 19 (63%) were non-smoker and molecular analyses were performed on 25 (74%) cases after SCLC transformation (20 driver mutations were found). In the SCLC coming from the EGFR mutant group, worse overall survival data were observed after the initial diagnosis with a statistically significant difference, 28 months [17-41] vs 49 months [36-118] in the non EGFR mutant group (p: 0.01). There was the same tendency towards worse survival data after transformation (8 [3-12] months vs 13 [6-15] months in the non EGFR mutant (p=0,06)).Conclusion: SCLC secondarily occuring in EGFR mutated patients appears to have a shorter survival than those occuring in non-mutated patients. In these patients, it is possible that there are 2 distinct cancers and not a transformation from the initial NSCLC. This new entity is only partially explained and molecular characteristics before and after transformation in SCLC is needed to better understand the mechanisms of this new disease and to optimize the treatment.