Table 2. Summary of the quantitative analysis of the dose volume histograms for the main structures over the entire cohort of patients for the reference intensity modulated proton plan and for the two variants with robust optimization to compensate for the ±3% CT calibration error and the 4 or 6mm positioning error.
| OARs | Objective | IMPT | IMPT p_4mm | IMPT p_6mm | P |
|---|---|---|---|---|---|
| CTV Volume: 105±72 [33–306] cm3 | |||||
| Dmean | 60Gy | 60.0 | 60.0 | 60.0 | - |
| D2% [Gy] | Minimize | 61.3±0.4 | 61.8±1.5 | 62.2±1.6 | a,b,c |
| D98% [Gy] | ≥58.8Gy (98%) | 59.0±0.3 | 59.0±0.4 | 58.7±0.6 | b,c |
| V95% [%] | Maximise | 99.9±0.1 | 99.9±0.1 | 99.8±0.7 | |
| HI [%] | <5% | 2.5±0.1 | 3.5±0.2 | 4.5±0.2 | a,b,c |
| PTV Volume: 228±125 [87–578] cm3 | |||||
| Dmean | 60Gy | 60.0±0.0 | 60.0±0.0 | 60.0±0.0 | - |
| D2% [Gy] | Minimize | 61.6±0.3 | 62.3±1.2 | 62.7±1.4 | a,b,c |
| D98% [Gy] | Maximize | 57.4±0.8 | 56.8±1.8 | 56.5±1.8 | a,b,c |
| V95% [%] | >95% | 98.5±1.0 | 97.2±3.5 | 96.6±3.8 | a |
| HI [%] | <10% | 4.7±0.2 | 6.0±0.3 | 7.1±0.3 | a,b,c |
| Healthy tissue Volume: 35830±11314 [17030–56305] cm3 | |||||
| V10Gy [%] | - | 2.5±1.2 | 2.2±1.1 | 2.3±1.1 | - |
| CI95% | - | 1.2±0.1 | 1.2±0.1 | 1.2±0.1 | - |
| Dose Integral [Gy∙ cm3 ∙105] |
- | 2.8±1.2 | 2.9±1.2 | 2.9±1.2 | - |
| Liver-PTV Volume: 1210±266 [725–1672] cm3 | |||||
| V<21Gy [cm3] | ≥ 700 cm3 | 1093±98 | 1089±105 | 1081±103 | a,b,c |
| Right kidney Volume: 157±62 [33–241] cm3 | |||||
| Dmean [Gy] | < 12 Gy | 0.4±0.4 | 0.4±0.8 | 0.4±0.9 | - |
| D65% [Gy] | <15 Gy | <0.1 | <0.1 | <0.1 | - |
| Right Lung: Volume: 1598±315 [1053–2280] cm3 | |||||
| Dmean [Gy] | <8 Gy | 2.9±2.6 | 2.9±2.5 | 2.9±2.4 | - |
| V20% [%] | <15% | 5.5±5.0 | 5.4±4.8 | 5.3±4.6 | - |
| Spinal cord Volume: 34±16 [12–76] cm3 | |||||
| D1% [Gy] | < 27 Gy | 0.6±1.3 | 1.1±2.1 | 1.1±2.2 | a |
| Stomach Volume: 163±58 [87–299] cm3 | |||||
| D1% [Gy] | < 36 Gy | 5.6±14.5 | 6.0±15.3 | 6.3±15.9 | c |
| Duodenum Volume: 69±41 [16–155] cm3 | |||||
| D1% [Gy] | < 36 Gy | 5.6±12.3 | 6.6±13.5 | 7.0±13.8 | - |
| Bowel bag Volume: 1161±659 [417–2833] cm3 | |||||
| Dmean [Gy] | Minimize | 0.4±0.8 | 0.4±1.0 | 0.4±1.0 | - |
| D1% [Gy] | < 36 Gy | 6.5±13.2 | 7.5±15.4 | 8.0±16.5 | - |
| Heart Volume: ± [–] cm3 | |||||
| Dmean [Gy] | <5 Gy | 0.9±1.1 | 1.1±1.2 | 1.1±1.2 | a,b |
| D1% [Gy] | < 35 Gy | 17.5±20.2 | 19.2±20.3 | 19.2±20.8 | a,b |
IMPT = intensity modulated proton therapy; Dx = dose received by x% or xcm3 of the volume. Dmean = mean dose, V<21Gy = volume receiving less then 21Gy. HI = conformity index. Statistical significance (p) a = IMPT vs IMPT p_4mm; b = IMPT vs IMPT p_6mm; c = IMPT p_4mm vs IMPT p_6mm