Table 3.
Comparison target volume and dose parameter of OARs in the initial and replanned IMRT
| Initial IMRT (mean ± SD) | Replanned IMRT (mean ± SD) | Decreased percent during IMRT (mean ± SD) | Z | P-value | |
|---|---|---|---|---|---|
| Target volume (cm3) | |||||
| Residual tumor | 7.4±14.9 | 4.2±7.5 | 14.3±54.5 | −1.682 | 0.093 |
| Surgical cavity | 47.6±20.6 | 19.2±10.4 | 61.1±14.8 | −2.934 | 0.003 |
| GTV | 55.0±27.5 | 23.5±11.8 | 57.1±15.3 | −2.934 | 0.003 |
| PTV1 | 104.4±41.4 | 59.3±24.6 | 43.0±12.8 | −2.943 | 0.003 |
| PTV2 | 301.8±75.6 | 214.7±51.2 | 28.3±7.2 | −2.943 | 0.003 |
| PTV3 | 439.0±76.7 | 335.2±51.1 | 23.2±7.3 | −2.201 | 0.028 |
| D2% to OARs (Gy) | |||||
| Brainstem | 46.6±11.1 | 38.6±13.8 | 20.6±13.1 | −2.845 | 0.004 |
| Optic chiasma | 35.3±12.5 | 27.4±9.0 | 23.8±18.4 | −2.667 | 0.008 |
| Pituitary gland | 27.8±7.2 | 22.1±8.6 | 30.4±23.1 | −2.756 | 0.006 |
| Ipsilateral lens | 5.1±2.3 | 4.3±1.1 | 20.4±15.3 | −2.580 | 0.010 |
| Contralateral lens | 4.4±1.5 | 3.6±1.3 | 18.2±15.5 | −2.402 | 0.016 |
| Ipsilateral optic nerve | 22.3±8.3 | 18.4±7.2 | 24.7±18.6 | −2.934 | 0.003 |
| Contralateral optic nerve | 21.8±7.5 | 16.8±6.3 | 33.8±22.7 | −2.934 | 0.003 |
| Ipsilateral hippocampus | 51.5±14.1 | 44.6±17.4 | 15.7±12.8 | −2.667 | 0.008 |
| Contralateral hippocampus | 42.6±15.2 | 28.8±14.8 | 33.3±19.4 | −2.845 | 0.004 |
| Ipsilateral cochlea | 24.6±9.3 | 15.1±5.8 | 37.7±32.0 | −2.758 | 0.010 |
| Contralateral cochlea | 13.4±4.2 | 8.2±4.0 | 30.2±24.8 | −2.490 | 0.013 |
| D50% to OARs (Gy) | |||||
| Ipsilateral hippocampus | 44.1±18.1 | 38.3±18.6 | 17.8±15.7 | −2.802 | 0.005 |
| Contralateral hippocampus | 28.2±15.6 | 20.11±13.7 | 28.9±15.5 | −2.845 | 0.004 |
| Ipsilateral cochlea | 16.8±8.2 | 10.2±4.9 | 39.7±25.9 | −2.845 | 0.004 |
| Contralateral cochlea | 10.7±3.5 | 6.2±3.7 | 35.2±23.4 | −2.934 | 0.003 |
| Vn (%) of healthy brain | |||||
| V10 | 72.6±11.0 | 61.2±12.7 | 15.7±11.3 | −2.576 | 0.006 |
| V20 | 50.8±10.0 | 39.9±10.2 | 20.8±17.2 | −2.576 | 0.006 |
| V30 | 32.1±9.0 | 23.3±5.7 | 26.0±14.4 | −2.845 | 0.004 |
| V40 | 16.8±6.1 | 10.3±3.0 | 35.2±15.1 | −2.845 | 0.004 |
| V50 | 5.2±3.8 | 2.1±1.6 | 52.5±24.9 | −2.803 | 0.005 |
Notes: D2%: near-maximum dose; D50%: median absorbed dose; and Vn (%): values of the relative volume of healthy brain tissue receiving at least nGy. Z is the statistic of the Wilcoxon two-related-sample test.
Abbreviations: GTV, gross tumor volume; IMRT, intensity-modulated radiotherapy; OARs, organs at risk; PTV1, planning target volume 1; PTV2, planning target volume 2; PTV3, planning target volume 3.