Inclusion Criteria:  Patients with histologically or cytologically confirmed extensive stage Small Cell Lung Cancer at time of initiation of treatment with atezolizumab and chemotherapy. Patients who were informed about the study and accepted for their data to be collected. Patients who received at least one dose of treatment with atezolizumab and chemotherapy as part of the French Early Access Program (ATU program) and have been accepted within this ATU program Selection period spans from May 6th 2019 until January 31st 2020 for initiation of treatment with atezolizumab and chemotherapy.  Exclusion Criteria:  Patients enrolled in a clinical trial assessing treatment with a combination of atezolizumab and chemotherapy. (ATU was granted to patients unable to meet eligibility criteria for on-going recruiting trials, unable to participate to other clinical trials, or because other medical interventions were not considered appropriate or acceptable). Patients who were included in the French Early Access Program (ATU program) but did not receive any atezolizumab and chemotherapy treatment.