Table 2.
Comparison of the dose–volume indices of PTV60 and OARs between SIB-IMRT and 3DCRT
| Dose index | 3DCRT | SIB-IMRT-D95% | SIB-IMRT-D50% | P-value |
|---|---|---|---|---|
| PTV60 | ||||
| Volume (ml) (IQR) | 138.8 (96.8, 188.1) | |||
| D98% (Gy) (IQR) | 54.3 (51.9, 56.1) | 58.9 (57.8, 59.3) | 53.7 (53.3, 54.0) | <0.001 |
| D50% (Gy) (IQR) | 60.4 (60.3, 61.0) | 62.4 (61.9, 63.0) | 60.1 (59.7, 60.3) | <0.001 |
| D2% (Gy) (IQR) | 63.5 (62.9, 63.7) | 64.8 (64.5, 65.8) | 63.1 (62.9, 63.7) | <0.001 |
| HI (IQR) | 0.135 (0.123, 0.182) | 0.115 (0.086, 0.126) | 0.155(0.150, 0.165) | <0.001 |
| CN (IQR) | 0.34 (0.32, 0.39) | 0.77 (0.72, 0.79) | 0.42 (0.36, 0.45) | <0.001 |
| Bilateral lungs | ||||
| Volume (ml) (IQR) | 2866 (2591, 3366) | |||
| V10Gy (%) (IQR) | 23.3 (21.5, 26.3) | 22.2 (20.2, 24.2) | 21.3 (19.7, 24.2) | 0.39 |
| V15Gy (%) (IQR) | 17.7 (16.1, 21.7) | 17.4 (15.5, 19.3) | 16.9 (15.5, 18.2) | 0.79 |
| V20Gy (%) (IQR) | 12.6 (11.4, 15.3) | 13.7 (12.3, 15.4) | 13.4 (12.5, 14.4) | 0.51 |
| PRVcord | ||||
| Volume (ml) (IQR) | 137.2 (127.1, 148.5) | |||
| Maximum dose (Gy) (IQR) | 49.5 (48.8, 49.9) | 48.8 (48.4, 49.2) | 49.2 (47.3, 51.2) | 0.22 |
| D2 cm3 (Gy) (IQR) | 46.6 (46.3, 47.2) | 44.4 (43.9, 45.4) | 45.2 (44.1, 46.8) | <0.001 |
| Thyroidout of PTV | ||||
| Volume (ml) (IQR) | 6.6 (3.8, 7.7) | |||
| V50Gy (%) (IQR) | 100 (98.7, 100) | 99.5 (98.5, 100) | 100 (100, 100) | 0.02 |
| V60Gy (%) (IQR) | 74.7 (48.3, 79.0) | 27.5 (16.4, 33.2) | 29.2 (15.9, 48.2) | 0.001 |
| Mean dose (Gy) (IQR) | 60.5 (59.4, 61.0) | 57.6 (56.3, 58.5) | 58.4 (57.8,59.9) | 0.007 |
| Brachial plexus | ||||
| Volume (ml) (IQR) | 6.6 (5.9, 8.6) | |||
| V60Gy (ml) (IQR) | 0 (0, 0) | 0 (0, 0.05) | 0 (0, 0) | Not applicable |
| D2 cm3 (Gy) (IQR) | 49.4 (48.5, 50.4) | 49.8 (48.8, 51.4) | 51.3 (50.5, 52.7) | 0.03 |
| Vout of PTV | ||||
| Maximum dose (IQR) | 64.6 (63.6, 65.1) | 65.6 (64.0, 66.6) | 64.0 (63.3, 64.7) | 0.20 |
| D2 cm3 (IQR) | 62.2 (61.8, 63.3) | 62.6 (61.9, 63.3) | 61.6 (61.1, 62.2) | 0.25 |
3DCRT = 3D conformal radiotherapy, HI = homogeneity index [20], CN = conformity number [21], Dx cm3 = the dose covering x cm3 of the structure volume, Dx% = the dose covering x% of the structure volume, IQR = interquartile range, OARs = organs at risk, PRVcord = the planning organs-at-risk volume of spinal cord, PTV60 = the sum of the planning target volume of the primary tumor and the metastatic lymph nodes, SIB-IMRT = simultaneous integrated boost intensity-modulated radiotherapy, SIB-IMRT-D50%: SIB-IMRT with the prescribed dose of 60 Gy delivered to 50% of PTV60, SIB-IMRT-D95%: SIB-IMRT with the prescribed dose of 60 Gy delivered to 95% of PTV60, Thyroidout of PTV = volume of the thyroid gland excluding the volume overlapping with the PTV60, Vout of PTV = volume of the body out of all planning target volumes, Vx Gy = the volume receiving x Gy.