Table 2.
Dosimetric parameters of the organs at risk in the three radiotherapy techniques studied
| OARs | Characteristics | IMRT | IMPT | IMCT |
p
(IMRT vs. IMPT |
p
(IMRT vs. IMCT) |
p
(IMPT vs. IMCT) |
|---|---|---|---|---|---|---|---|
| Spinal cord | Dmax (Gy) | 48.5 ± 9.5 | 37.3 ± 7.4 | 34.3 ± 8.2 | < 0.001 | < 0.001 | < 0.001 |
| D1% (Gy) | 43.8 ± 9.4 | 30.8 ± 7.7 | 28.3 ± 8.8 | < 0.001 | < 0.001 | 0.001 | |
| MBT | Dmax (Gy) | 72.8 ± 1.1 | 71.4 ± 0.6 | 72.2 ± 0.9 | < 0.001 | 0.048 | 0.001 |
| D1% (Gy) | 71.4 ± 0.8 | 69.6 ± 0.7 | 70.1 ± 1.3 | < 0.001 | < 0.001 | 0.017 | |
| Heart | Dmean (Gy) | 14.7 ± 13.3 | 4.9 ± 4.2 | 5.8 ± 5.1 | < 0.001 | < 0.001 | 0.031 |
| V5 (%) | 44.7 ± 40.4 | 14.5 ± 11.3 | 20.2 ± 16.9 | 0.001 | 0.001 | 0.011 | |
| V10 (%) | 40.3 ± 38.8 | 11.5 ± 9.3 | 12.8 ± 10.7 | 0.002 | 0.002 | 0.031 | |
| V20 (%) | 30.1 ± 29.7 | 8.2 ± 7.0 | 8.7 ± 7.6 | 0.005 | 0.002 | 0.061 | |
| V30 (%) | 23.6 ± 24.4 | 6.3 ± 5.6 | 6.6 ± 5.8 | 0.003 | 0.003 | 0.041 | |
| V40 (%) | 12.5 ± 13.0 | 5.0 ± 4.7 | 5.1 ± 4.9 | 0.005 | 0.005 | 0.19 | |
| V50 (%) | 6.3 ± 6.2 | 4.0 ± 4.1 | 4.1 ± 4.3 | 0.005 | 0.005 | 0.40 | |
| V60 (%) | 4.5 ± 4.8 | 3.1 ± 3.4 | 3.2 ± 3.6 | 0.003 | 0.004 | 0.048 | |
| Lungs | Dmean (Gy) | 12.4 ± 4.9 | 8.6 ± 3.4 | 8.9 ± 3.4 | 0.002 | 0.003 | 0.037 |
| V5 (%) | 46.1 ± 18.3 | 31.0 ± 11.4 | 32.2 ± 12.1 | 0.001 | 0.002 | 0.093 | |
| V10 (%) | 37.3 ± 15.5 | 25.9 ± 9.8 | 25.9 ± 9.8 | 0.002 | 0.002 | 0.74 | |
| V20 (%) | 28.0 ± 12.5 | 18.2 ± 7.7 | 19.0 ± 7.3 | 0.002 | 0.002 | 0.31 | |
| V30 (%) | 15.1 ± 8.2 | 11.0 ± 6.1 | 13.3 ± 6.0 | 0.057 | 0.43 | 0.005 | |
| V40 (%) | 5.4 ± 3.7 | 5.1 ± 2.8 | 6.0 ± 3.1 | 0.91 | 0.17 | 0.017 | |
| V50 (%) | 2.8 ± 1.9 | 3.0 ± 1.7 | 3.0 ± 1.6 | 0.53 | 0.33 | 0.17 | |
| V60 (%) | 1.8 ± 1.2 | 2.0 ± 1.3 | 2.0 ± 1.1 | 0.25 | 0.13 | 0.71 |
Abbreviations: OARs, organs at risk; Dmax, maximum dose; D1%, the dose that 1% of the volume received of the OARs; Dmean, mean dose; Vx, the percentage volume of the organs at risk receiving ≥ x Gy irradiation; MBT, main bronchial tree; IMRT, intensity modulated x-ray radiotherapy; IMPT, intensity modulated proton radiotherapy; IMCT, intensity modulated carbon-ion radiotherapy. *Doses are presented as the RBE (relative biological effectiveness)-weighted dose