[1] Univ Hosp Essen, Dept Particle Therapy, West German Proton Therapy Ctr Essen WPE, West German Canc Ctr WTZ, Essen, Germany
[2] Univ Hosp Essen, West German Proton Therapy Ctr Essen WPE, West German Canc Ctr WTZ, Essen, Germany
[3] Univ Duisburg Essen, Univ Hosp Essen, Div Clin Neurooncol, Dept Neurol,DKFZ Div Translat Neurooncol, Essen, Germany
[4] German Canc Consortium DKTK, Essen, Germany