Atezolizumab After Concurrent Chemo-radiotherapy Versus Chemo-radiotherapy Alone in Limited Disease Small-cell Lung Cancer

Inclusion Criteria: * Histologically or cytologically confirmed small-cell lung cancer * Previous radiotherapy to the thorax is allowed as long as the patient can receive TRT of 45 Gy. * Stage I-III according to TNM v8 ineligible for surgery provided all lesions can be included in a tolerable radiotherapy field ("limited disease") * ECOG performance status 0-2 * Measureable disease according to the RECIST 1.1 * Adequate organ function defined as: (a) Serum alanine transaminase (ALT) ≤ 2.5 x upper limit of normal (ULN); (b) Total serum bilirubin ≤ 1.5 x ULN; (c)Absolute neutrophil count (ANC) ≥ 1.5 x 10 superscr 9/L; (d) Platelets ≥ 100 x 10 superscr 9/L ; (e) Creatinine \< 100 µmol/L and calculated creatinine-clearance \> 50 ml/min. If calculated creatinine-clearance is \< 50 ml/min, an EDTA clearance should be performed * No malignant cells in pericardial or pleural fluid (at least 1 sample should be obtained if pleural fluid is present) If there is so little fluid that it cannot easily be collected, the patient is considered eligible. * Pulmonary function: FEV1 \> 1 l or \> 30 % of predicted value and DLCO \> 30 % of predicted value * Female patients of childbearing potential (Postmenarcheal, not postmenopausal (\>12 continuous months of amenorrhea with no identified cause other than menopause), and no surgical sterilization) should use highly effective contraception and take active measures to avoid pregnancy while undergoing atezolizumab treatment and for at least 5 mont…