Figure 4.

Comparison of plan robustness between intensity‐modulated proton therapy (IMPT) and volumetric‐modulated arc therapy (VMAT) plans using the widths of the dose volume histogram (DVH) band pairs in the presence of uncertainties. (a) clinical target volume (CTV_high) D_95% and ${\mathrm{D}}_{2\mathrm{c}{\mathrm{m}}^3}$, and CTV_low D_95% normalized to the prescription dose. (b) CTV_high D_5%‐D_95% normalized to the prescription dose. (c) Kidney V_18Gy[RBE] and liver V_30Gy[RBE] in relative volume. (d) Stomach V_45Gy[RBE] in absolute volume. (e) Lung D_mean, cord D_max and ${\mathrm{D}}_{0.03\mathrm{c}{\mathrm{m}}^3}$ _, heart D_mean, and liver D_mean in absolute dose. (f) Lung V_5Gy[RBE] and V_20Gy[RBE], heart V_20Gy[RBE], V_30Gy[RBE] and V_40Gy[RBE] in relative volume. In each box plot, the five horizontal lines from top to bottom are the maximum, third quartile, median, first quartile, and minimum value of the DVH band widths in the presence of uncertainties of the corresponding DVH index for the whole group excluding the outliers respectively. The grey points are the outliers as defined in Statistical Analysis subsection. Numbers at the top of the columns are P‐values from Wilcoxon rank sum testing. The blue boxes are the IMPT results and white boxes are the VMAT results. Abbreviations: RBE = relative biological effectiveness.