Table 2.
Summary comparison of VMAT and HT plans
| Structure/Item | Metric | VMAT | HT | p -value |
|---|---|---|---|---|
| PTV |
DV95% (Gy) |
49.3 ± 0.1 |
49.8 ± 0.1 |
<0.001 |
| DHI |
0.147 ± 0.009 |
0.096 ± 0.005 |
<0.001 |
|
| CI |
0.778 ± 0.008 |
0.719 ± 0.008 |
<0.001 |
|
| TCP |
99.8 ± 0.2 |
100 ± 0.0 |
0.002 |
|
| Total lung |
V5Gy (%) |
66.2 ± 3.1 |
89.8 ± 1.4 |
<0.001 |
| V20Gy (%) |
16.3 ± 0.2 |
15.0 ± 0.3 |
<0.001 |
|
| NTCP (%) |
0.3 ± 0.1 |
0.6 ± 0.1 |
0.06 |
|
| SCCP (%) |
5.3 ± 0.1 |
6.1 ± 0.0** |
<0.001 |
|
| Ipsilateral lung |
V5Gy (%) |
96.9 ± 1.3 |
99.3 ± 0.5 |
0.06 |
| V20Gy (%) |
32.3 ± 0.8 |
29.9 ± 1.0 |
<0.001 |
|
| Contralateral lung |
V5Gy (%) |
37.8 ± 4.9 |
81.7 ± 2.5 |
<0.001 |
| Heart* |
V15Gy (%) |
26.0 ± 1.9 |
28.2 ± 2.6 |
0.4 |
| Dmean (Gy) |
12.9 ± 0.5 |
14.4 ± 0.6 |
0.04 |
|
| Dmax (Gy) |
42.2 ± 1.6 |
38.3 ± 1.3 |
<0.001 |
|
| NTCP (%) |
1.3 ± 0.2 |
0.9 ± 0.1 |
0.008 |
|
| Contralateral breast |
Mean dose (Gy) |
1.5 ± 0.1 |
1.8 ± 0.1 |
<0.001 |
| SCCP (%) |
1.0 ± 0.0** |
1.2 ± 0.0** |
<0.001 |
|
| Non-specific normal tissue |
Mean dose (Gy) |
7.0 ± 0.2 |
11.1 ± 0.4 |
<0.001 |
| SCCP (%) |
0.7 ± 0.0 |
0.9 ± 0.0** |
<0.001 |
|
| Efficiency | Delivery time (s) | 128.6 ± 2.8 | 382.4 ± 10.9 | <0.001 |
Values shown are averages of the 15 patients (± 1σ) with the exception of the heart.
*Patients with right-side mastectomy excluded.
**Standard deviation of the mean < 0.05.
Abbreviations: PTV planning target volume, DHI dose homogeneity index (ideal = 0), CI conformity index (ideal = 1), TCP tumor control probability, NTCP normal tissue complication probability, SCCP secondary cancer complication probability.