Table 5.
Univariate and multivariate analyses of dosimetric parameters.
| T stage | N stage | PGTVnx volume | PGTVnd volume | RT modality | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| B | p | B | p | B | p | B | p | B | p | |
| Univariate analysis | ||||||||||
| PGTVnx_D95 | -77.977 | 0.001 | 45.829 | 0.002 | -0.779 | 0.015 | 0.307 | 0.142 | 42.500 | 0.085 |
| PGTVnx_HI | 0.023 | 0.000 | -0.010 | 0.011 | 0.000 | 0.000 | 0.000 | 0.205 | -0.006 | 0.309 |
| PGTVnd_D95 | -5.858 | 0.678 | 12.063 | 0.213 | -0.201 | 0.271 | -0.318 | 0.006 | 59.625 | 0.000 |
| PGTVnd_HI | 0.005 | 0.162 | 0.005 | 0.022 | 0.000 | 0.519 | 0.000 | 0.002 | -0.020 | 0.000 |
| PGTVnx+nd_CI | -0.015 | 0.177 | 0.004 | 0.555 | 0.000 | 0.882 | 0.000 | 0.609 | 0.043 | 0.000 |
| PTV1_D95 | -2.862 | 0.902 | 32.231 | 0.022 | -0.012 | 0.968 | 0.323 | 0.094 | -36.407 | 0.110 |
| PTV1_HI | 0.005 | 0.252 | -0.005 | 0.104 | 0.000 | 0.045 | 0.000 | 0.362 | -0.005 | 0.247 |
| PTV1_CI | 0.079 | 0.000 | -0.078 | 0.000 | 0.001 | 0.000 | -0.001 | 0.000 | 0.059 | 0.004 |
| PTV2_D95 | -5.591 | 0.796 | 11.544 | 0.389 | 0.492 | 0.077 | 0.228 | 0.206 | 116.780 | 0.000 |
| PTV2_HI | 0.006 | 0.260 | -0.005 | 0.130 | 0.000 | 0.169 | 0.000 | 0.005 | -0.029 | 0.000 |
| PTV2_CI | -0.002 | 0.755 | 0.004 | 0.743 | 0.000 | 0.726 | 0.000 | 0.665 | -0.022 | 0.004 |
| Spinal cord_ Dmax | 134.805 | 0.066 | 30.194 | 0.508 | 0.662 | 0.489 | 1.032 | 0.094 | -392.500 | 0.000 |
| Spinal cord_ D1cc | 125.954 | 0.081 | 26.091 | 0.560 | 0.378 | 0.687 | 0.893 | 0.141 | -384.963 | 0.000 |
| Spinal cord PRV_ Dmax | 190.146 | 0.025 | 40.823 | 0.441 | 3.242 | 0.003 | 0.879 | 0.221 | -187.222 | 0.026 |
| Spinal cord PRV_ D1cc | 121.504 | 0.103 | 42.256 | 0.327 | 1.381 | 0.152 | 0.951 | 0.128 | -340.981 | 0.000 |
| Brainstem_ Dmax | 62.193 | 0.130 | -2.346 | 0.927 | 1.645 | 0.002 | 0.555 | 0.107 | -14.444 | 0.724 |
| Brainstem_ D1cc | 83.735 | 0.164 | 0.289 | 0.994 | 1.857 | 0.016 | 0.728 | 0.150 | -198.278 | 0.001 |
| Brainstem PRV_ Dmax | 102.743 | 0.019 | 3.742 | 0.892 | 1.876 | 0.001 | 0.221 | 0.554 | -4.556 | 0.918 |
| Brainstem PRV_ D1cc | 122.580 | 0.017 | 0.148 | 0.996 | 2.490 | 0.000 | 0.671 | 0.123 | -75.704 | 0.141 |
| Optic chiasm_Dmax | 1129.771 | 0.000 | -369.329 | 0.004 | 9.562 | 0.000 | -4.562 | 0.009 | 442.611 | 0.033 |
| Optic nerve I_Dmax | 1041.180 | 0.000 | -450.376 | 0.001 | 8.084 | 0.006 | -4.769 | 0.013 | 646.278 | 0.004 |
| Optic nerve C_Dmax | 653.890 | 0.001 | -269.370 | 0.025 | 6.241 | 0.013 | -3.508 | 0.032 | 650.000 | 0.001 |
| Lens PRV I_Dmax | 215.802 | 0.001 | -100.740 | 0.014 | 3.048 | 0.000 | -1.037 | 0.064 | -52.148 | 0.434 |
| Lens PRV C_Dmax | 142.478 | 0.000 | -68.125 | 0.002 | 1.754 | 0.000 | -0.606 | 0.043 | -93.759 | 0.008 |
| Temporal lobe I_ Dmax | 311.609 | 0.000 | -91.244 | 0.020 | 3.035 | 0.000 | -0.997 | 0.063 | 12.222 | 0.848 |
| Temporal lobe C_ Dmax | 98.898 | 0.247 | -55.652 | 0.291 | 2.590 | 0.018 | -0.375 | 0.601 | -55.667 | 0.512 |
| Parotid gland I_Dmean | -16.580 | 0.906 | 91.524 | 0.292 | 1.936 | 0.288 | 1.810 | 0.124 | -230.093 | 0.098 |
| Parotid gland I_V30Gy | 1.456 | 0.647 | 0.838 | 0.670 | 0.051 | 0.210 | 0.025 | 0.346 | -8.654 | 0.005 |
| Parotid gland C_Dmean | -19.280 | 0.863 | -20.147 | 0.769 | -1.612 | 0.262 | -0.641 | 0.492 | -427.889 | 0.000 |
| Parotid gland C_V30Gy | -1.039 | 0.703 | 0.153 | 0.928 | -0.014 | 0.686 | -0.008 | 0.739 | -10.920 | 0.000 |
| Multivariate analysis | ||||||||||
| PGTVnx_D95 | -33.906 | 0.241 | 34.620 | 0.032 | -0.494 | 0.149 | – | – | 44.873 | 0.055 |
| PGTVnx_HI | 0.010 | 0.166 | -0.005 | 0.170 | 0.000 | 0.004 | – | – | – | – |
| PGTVnd_D95 | – | – | – | – | – | – | -0.293 | 0.005 | 57.875 | 0.000 |
| PGTVnd_HI | – | – | 0.002 | 0.464 | – | – | 0.000 | 0.013 | -0.019 | 0.000 |
| PGTVnx+nd_CI | – | – | – | – | – | – | – | – | 0.043 | 0.000 |
| PTV1_D95 | – | – | 28.305 | 0.113 | – | – | 0.087 | 0.719 | – | – |
| PTV1_HI | – | – | – | – | 0.000 | 0.045 | – | – | – | – |
| PTV1_CI | -0.001 | 0.956 | -0.031 | 0.007 | 0.001 | 0.000 | -0.001 | 0.000 | 0.048 | 0.000 |
| PTV2_D95 | – | – | – | – | 0.411 | 0.083 | – | – | 115.072 | 0.000 |
| PTV2_HI | – | – | – | – | – | – | 0.000 | 0.000 | -0.030 | 0.000 |
| PTV2_CI | – | – | – | – | – | – | – | – | -0.022 | 0.004 |
| Spinal cord_ Dmax | 141.497 | 0.027 | – | – | – | – | 1.101 | 0.039 | -377.148 | 0.000 |
| Spinal cord_ D1cc | 104.530 | 0.092 | – | – | – | – | – | – | -379.156 | 0.000 |
| Spinal cord PRV_ Dmax | 76.091 | 0.404 | – | – | 2.902 | 0.015 | – | – | -192.936 | 0.018 |
| Spinal cord PRV_ D1cc | – | – | – | – | – | – | – | – | -340.981 | 0.000 |
| Brainstem_ Dmax | – | – | – | – | 1.645 | 0.002 | – | – | – | – |
| Brainstem_ D1cc | – | – | – | – | 1.976 | 0.007 | – | – | -205.048 | 0.000 |
| Brainstem PRV_ Dmax | – | – | – | – | 1.64 | 0.007 | – | – | – | – |
| Brainstem PRV_ D1cc | 43.208 | 0.432 | – | – | 2.233 | 0.002 | – | – | – | – |
| Optic chiasm_Dmax | 978.266 | 0.000 | 99.248 | 0.502 | 4.307 | 0.101 | -3.673 | 0.055 | 464.566 | 0.008 |
| Optic nerve I_Dmax | 874.116 | 0.001 | -71.264 | 0.674 | 2.618 | 0.383 | -2.444 | 0.264 | 663.963 | 0.001 |
| Optic nerve C_Dmax | 533.102 | 0.015 | 36.690 | 0.804 | 3.194 | 0.225 | -2.735 | 0.154 | 652.785 | 0.000 |
| Lens PRV I_Dmax | 88.195 | 0.251 | -19.396 | 0.714 | 2,587 | 0.006 | -0.873 | 0.201 | – | – |
| Lens PRV C_Dmax | 55.794 | 0.145 | -26.928 | 0.304 | 1.455 | 0.002 | -0.418 | 0.215 | -100.483 | 0.001 |
| Temporal lobe I_ Dmax | 243.160 | 0.001 | 25.905 | 0.588 | 1.796 | 0.035 | -0.886 | 0.151 | – | – |
| Temporal lobe C_ Dmax | – | – | – | – | 2.590 | 0.018 | – | – | – | – |
| Parotid gland I_Dmean | – | – | – | – | – | – | – | – | -230.093 | 0.098 |
| Parotid gland I_V30Gy | – | – | – | – | – | – | – | – | -8.654 | 0.005 |
| Parotid gland C_Dmean | – | – | – | – | – | – | – | – | -427.889 | 0.000 |
| Parotid gland C_V30Gy | – | – | – | – | – | – | – | – | -10.920 | 0.000 |
RT, radiotherapy; 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.