Extension of TOPAS for the simulation of proton radiation effects considering molecular and cellular endpoints

Polster, L.*; Schuemann, J.*; Rinaldi, I.*; Burigo, L.*; McNamara, A. L.*; Steward, R. D.*; Attili, A.*; Carlson, D. J.*; Sato, Tatsuhiko   ; Ramos Mndez, J.*; Faddegon, B.*; Perl, J.*; Paganetti, H.*

The aim of this work is to extend a widely used proton Monte Carlo tool, TOPAS, towards the modeling of relative biological effect (RBE) distributions in experimental arrangements as well as patients. Then, eight biophysical models was incorporated into TOPAS. As far as physics parameters are concerned, four of these models are based on the proton linear energy transfer (LET), while the others are based on DNA Double Strand Break (DSB) induction and the frequency-mean specific energy, lineal energy, or delta electron generated track structure. The model on the basis of lineal energy adapted a microdosimetric function developed by JAEA. This work is an important step in bringing biologically optimized treatment planning for proton therapy closer to the clinical practice.