Statistical analysis
We employed a Welch design without interim analyses based on the data acquired in the prequel study assuming a 4.5 Gy difference in threshold isodoses of fRILI between patient groups (Seidensticker et al. Permuted block randomization was performed at the local Institute of Biometry using the Mersenne twister in RITA 1.24, EvidatAll statistical analyses were performed in IBM SPSS Statistics 22.0