Quantitative analysis of robustness‐based versus LET‐based optimization in intensity‐modulated proton therapy for pediatric brain tumors

An inherent conflict between robust target coverage and high LET in the target in IMPT planning was demonstrated in our study for pediatric brain tumor patients. Robust optimization resulted in lower LET not only in the target but also in nearby critical structures, such as brainstem and spinal cord. In contrast, LET optimization improved the LET distribution but worsened the plan robustness compared to nominal optimization. The trade-off effect between LET enhancement and plan robustness can vary in respect to anatomical relationships and needs to be carefully evaluated in IMPT planning.