[1] Paul Scherrer Inst, Ctr Proton Therapy, Villigen, Switzerland
[2] Univ Hosp Bern, Inselspital, Bern, Switzerland
[3] Univ Bern, Radiat Oncol, Bern, Switzerland
[4] Univ Maryland, Radiat Oncol, Baltimore, MD 21201 USA
[5] Univ Hosp Essen, West German Proton Therapy Ctr, Essen, Germany
[6] Univ Hospial Munster, Paediat Haematol & Oncol, Munster, Germany