Immunotherapy in small cell lung cancer: one step at a time: a narrative review - Dumoulin, Daphne W.; Dingemans, Anne-Marie C.; Aerts, Joachim G. J. V.; Remon, Jordi; De Ruysscher, Dirk K. M.; Hendriks, Lizza E. L. (Translational Lung Cancer Research; Vol 10, No 6 (June 29, 2021): Translational Lung Cancer Research, 2020)