A preliminary study comparing planning target volume-based optimization and robust optimization

Robust optimization (RO) makes intensity-modulated proton treatment (IMPT) plans has less sensitivity to proton uncertainties and provides better target dose coverage and even dose homogeneity without compromising critical-organ sparing compared to the plans generated by planning target volume (PTV)-based optimization. In this study, we compared the results between PTV-based and robust optimization on four cases including head-and-neck and lung regions for better understanding the difference in treatment planning optimization of IMPT on Eclipse treatment planning system. The planning results of RO demonstrated better robust outcome in defiance of proton uncertainties compared to PTV-based optimization. Besides, RO’s plans had better target dose coverage by increasing 1.5 Gy (RBE) on average to D95% of CTV than PTV-based optimization, and provide more homogeneous dose distributions by improving HI (D5%/D95%) from 0.03 to 0.04. The comparison results in this study show the superiority of RO was not due to incorporate safety margins for critical organs, but mainly the ability to compensate the dose perturbations caused by proton uncertainties.