Table 4.
Dosimetric comparisons of the matched VMAT and tomotherapy groups.
| VMAT (Mean ± SD) | Tomotherapy (Mean ± SD) | p | |
|---|---|---|---|
| PGTVnx_D95 (cGy) | 6979 ± 140 | 7022 ± 112 | 0.085 |
| PGTVnx_HI | 0.1034 ± 0.0379 | 0.0969 ± 0.0265 | 0.309 |
| PGTVnd_D95 (cGy) | 7045 ± 52 | 7104 ± 71 | 0.000 |
| PGTVnd_HI | 0.0874 ± 0.0159 | 0.0677 ± 0.0150 | 0.000 |
| PGTVnx+nd_CI | 0.7941 ± 0.0598 | 0.8373 ± 0.0403 | 0.000 |
| PTV1_D95 (cGy) | 6320 ± 127 | 6284 ± 106 | 0.110 |
| PTV1_HI | 0.1968 ± 0.0297 | 0.1914 ± 0.0159 | 0.245 |
| PTV1_CI | 0.3755 ± 0.0954 | 0.4345 ± 0.1116 | 0.004 |
| PTV2_D95 (cGy) | 5546 ± 94 | 5663 ± 93 | 0.000 |
| PTV2_HI | 0.3379 ± 0.0250 | 0.3092 ± 0.0171 | 0.000 |
| PTV2_CI | 0.7901 ± 0.0404 | 0.7682 ± 0.0368 | 0.004 |
| Spinal cord_Dmax (cGy) | 3738 ± 331 | 3346 ± 317 | 0.000 |
| Spinal cord_D1cc (cGy) | 3485 ± 300 | 3100 ± 336 | 0.000 |
| Spinal cord PRV_Dmax (cGy) | 4406 ± 481 | 4219 ± 375 | 0.026 |
| Spinal cord PRV_D1cc (cGy) | 3873 ± 350 | 3532 ± 339 | 0.000 |
| Brainstem_Dmax (cGy) | 5293 ± 212 | 5278 ± 212 | 0.724 |
| Brainstem_D1cc (cGy) | 4757 ± 310 | 4559 ± 278 | 0.001 |
| Brainstem PRV_Dmax (cGy) | 5890 ± 215 | 5885 ± 241 | 0.918 |
| Brainstem PRV_D1cc (cGy) | 5185 ± 258 | 5109 ± 273 | 0.141 |
| Optic chiasm_Dmax (cGy) | 5479 ± 1183 | 5922 ± 938 | 0.033 |
| Optic nerve I_Dmax (cGy) | 5499 ± 1412 | 6145 ± 815 | 0.004 |
| Optic nerve C_Dmax (cGy) | 5054 ± 1205 | 5704 ± 613 | 0.001 |
| Lens PRV I_Dmax (cGy) | 935 ± 249 | 883 ± 400 | 0.435 |
| Lens PRV C_Dmax (cGy) | 860 ± 163 | 766 ± 194 | 0.008 |
| Temporal lobe I_ Dmax (cGy) | 7388 ± 375 | 7399 ± 279 | 0.848 |
| Temporal lobe C_ Dmax (cGy) | 6964 ± 401 | 6908 ± 474 | 0.512 |
| Parotid gland I_Dmean (cGy) | 4153 ± 669 | 3923 ± 760 | 0.098 |
| Parotid gland I_V30Gy (%) | 65.23 ± 15.66 | 57.14 ± 15.90 | 0.005 |
| Parotid gland C_Dmean (cGy) | 4035 ± 611 | 3607 ± 434 | 0.000 |
| Parotid gland C_V30Gy (%) | 62.47 ± 15.12 | 51.55 ± 10.11 | 0.000 |
VMAT, volumetric modulated arc therapy; PGTVnx, planning target volume of the nasopharynx; PGTVnd, planning target volume of the lymph nodes; PTV1, planning target volume of high-risk region; PTV2, planning target volume of low-risk region; D95, the minimum dose delivered to 95% of the PTVs; HI, homogeneity index; CI, conformity index; Dmax, maximum dose; D1cc, maximum dose encompassing 1cc of the structure; I, ipsilateral; C, contralateral; Dmean, mean dose; V30Gy, the relative volume of the structure receiving over 30Gy.