Table 3.
Plan parameters and significance of differences based on the pooled data of five patients and five institutes
| 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 |
* Standard deviations (SDs) are given as absolute values.
^ Hypothesis testing using a paired t-test results in almost identical significances at 95% confidence level.
$ The contralateral submandibular gland was delineated in only three patients.
° Not all institutes used objectives to control dose for these structures.
# Based on effective delivery times reported by four institutes.