ESTRO PT 2018

Biological uncertainties

• A two-beam IMPT plan for brain tumor optimized based on criteria defined in terms of constant RBE of 1.1 (squares) and in terms of variable RBE computed using a model published byWilkens, et al. (triangles). After optimization, both dose distributions were converted to variable RBE- weighted dose for comparison. R. Mohan, D. Grosshans, Proton therapy – Present and future, Adv. Drug Deliv. Rev. (2016) Over the last years 3 publications of unexpected brain image alterations or brain necrosis at presumably safe Gy(RBE) levels in children undergoing proton therapy for CNS tumors