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Table 3 Plan parameters and significance of differences based on the pooled data of five patients and five institutes

From: Multi-institutional comparison of volumetric modulated arc therapy vs. intensity-modulated radiation therapy for head-and-neck cancer: a planning study

   VMAT average ± 1 SD* IMRT average ± 1 SD* Average difference ± 1 SD* (VMAT – IMRT) p-value (Wilcoxon’s signed-rank test)^
PTVboost CI95 1.37 ± 0.08 1.45 ± 0.11 -0.08 ± 0.09 .001
PTVtotal CI95 1.50 ± 0.09 1.62 ± 0.10 -0.12 ± 0.07 < .001
Normal tissue V5Gy (cm3) 5050 ± 730 5030 ± 750 -20 ± 260 n.s.
V10Gy (cm3) 4050 ± 630 3970 ± 590 -80 ± 160 n.s.
V20Gy (cm3) 2830 ± 510 2860 ± 480 30 ± 150 n.s.
Spinal cord Dmax (Gy) 45.1 ± 3.5 46.6 ± 3.0 -1.5 ± 2.3 .001
D1% (Gy) 43.4 ± 3.7 44.4 ± 3.5 -0.9 ± 2.2 .005
Dmean (Gy) 29.3 ± 4.4 29.8 ± 3.6 -0.5 ± 2.4 n.s.
Brain stem Dmax (Gy) 46.4 ± 5.4 47.1 ± 4.7 -0.7 ± 4.6 n.s.
D1% (Gy) 43.8 ± 5.8 44.0 ± 5.5 -0.2 ± 4.9 n.s.
Dmean (Gy) 13.6 ± 3.6 14.5 ± 4.3 -1.0 ± 2.4 n.s.
Parotid gland ipsilateral V25Gy (%) 42.9 ± 15.6 50.3 ± 20.0 -7.4 ± 14.0 < .001
V39Gy (%) 30.0 ± 14.6 35.9 ± 18.6 -5.9 ± 11.2 < .001
Dmean (Gy) 28.0 ± 7.5 31.1 ± 9.1 -3.1 ± 5.1 < .001
Parotid gland contralateral V25Gy (%) 31.0 ± 7.1 34.5 ± 6.8 -3.5 ± 3.6 < .001
V39Gy (%) 18.3 ± 6.0 20.8 ± 6.1 -2.5 ± 2.5 < .001
Dmean (Gy) 22.0 ± 2.9 23.3 ± 2.8 -1.3 ± 1.5 < .001
Submandibular gland contralateral$ V39Gy (%) 88.1 ± 15.3 90.8 ± 13.5 -2.7 ± 6.9 n.s.
V60Gy (%) 16.4 ± 21.4 21.8 ± 27.3 -5.5 ± 8.5 .020
Dmean (Gy) 53.0 ± 5.9 54.2 ± 6.1 -1.3 ± 1.8 .027
Oral cavity V25Gy (%) 79.8 ± 22.9 86.3 ± 15.7 -6.5 ± 10.2 .011
V39Gy (%) 40.6 ± 22.0 48.8 ± 23.3 -8.2 ± 12.4 .002
Dmean (Gy) 36.7 ± 7.8 39.4 ± 7.3 -2.7 ± 2.8 < .001
Larynx V39Gy (%) 75.4 ± 24.7 79.1 ± 21.6 -3.8 ± 6.7 .012
V45Gy (%) 54.1 ± 27.4 58.2 ± 26.5 -4.1 ± 9.3 n.s.
Dmean (Gy) 45.5 ± 5.3 46.5 ± 4.4 -1.0 ± 1.5 .004
Pharyngeal constrictors° V39Gy (%) 78.7 ± 24.5 81.5 ± 20.0 -2.8 ± 15.2 n.s.
V45Gy (%) 59.7 ± 29.4 57.5 ± 25.5 2.2 ± 19.9 n.s.
Dmean (Gy) 47.1 ± 5.3 46.9 ± 3.8 0.2 ± 2.7 n.s.
Mandible° V39Gy (%) 74.0 ± 13.1 78.2 ± 11.8 -4.2 ± 8.4 .025
V60Gy (%) 25.7 ± 15.0 30.1 ± 16.2 -4.4 ± 5.1 < .001
Dmean (Gy) 48.6 ± 5.5 50.3 ± 5.7 -1.7 ± 1.7 < .001
Effective delivery time# (min:sec) 5:54 ± 1:05 13:15 ± 1:38 -7:21 ± 1:55 < .001
MUs -- 643 ± 111 828 ± 149 -185 ± 129 < .001
  1. * Standard deviations (SDs) are given as absolute values.
  2. ^ Hypothesis testing using a paired t-test results in almost identical significances at 95% confidence level.
  3. $ The contralateral submandibular gland was delineated in only three patients.
  4. ° Not all institutes used objectives to control dose for these structures.
  5. # Based on effective delivery times reported by four institutes.