Table 5.
Dosimetric comparisons for OARs between VMAT and PBS.
| Organ | Parameter | VMAT | PBS (Gy(RBE)) | P-value |
|---|---|---|---|---|
| Rectum | V30Gy (%) | 69.90 ± 5.69 | 46.89 ± 14.68 | 0.010* |
| V40Gy (%) | 49.78 ± 11.50 | 34.52 ± 13.86 | 0.001* | |
| V50Gy (%) | 34.74 ± 11.35 | 24.60 ± 11.40 | 0.007* | |
| V60Gy (%) | 22.22 ± 8.94 | 17.80 ± 9.39 | 0.034* | |
| V70Gy (%) | 12.11 ± 6.41 | 11.82 ± 7.08 | 0.657 | |
| V75Gy (%) | 7.83 ± 4.94 | 8.60 ± 5.56 | 0.135 | |
| D1% (Gy) | 79.21 ± 2.45 | 78.28 ± 4.46 | 0.408 | |
| Dmean (Gy) | 42.68 ± 4.60 | 33.60 ± 7.64 | 0.003* | |
| Vol. overlap with PTV1 (cm3): 3.57 ± 2.28 (0.01–6.17) | ||||
| Vol. overlap with PTV2 (cm3): 1.58 ± 1.27 (0.01–3.09) | ||||
| Bladder | V35Gy (%) | 72.89 ± 6.24 | 44.99 ± 2.27 | 0.000* |
| V40Gy (%) | 54.62 ± 1.89 | 40.11 ± 1.72 | 0.000* | |
| V50Gy (%) | 30.57 ± 5.13 | 26.26 ± 2.84 | 0.018* | |
| V60Gy (%) | 20.95 ± 2.82 | 20.04 ± 2.45 | 0.111 | |
| V70Gy (%) | 14.21 ± 1.36 | 14.73 ± 1.76 | 0.207 | |
| V75Gy (%) | 11.43 ± 1.30 | 11.69 ± 1.29 | 0.34 | |
| D1% (Gy) | 81.55 ± 0.48 | 81.67 ± 0.24 | 0.488 | |
| Dmean (Gy) | 46.51 ± 0.89 | 32.47 ± 1.03 | 0.000* | |
| Vol. overlap with PTV1 (cm3): 32.12 ± 12.36 (20.61–48.69) | ||||
| Vol. overlap with PTV2 (cm3): 12.19 ± 2.21 (9.24–14.62) | ||||
| Bowel cavity | V20Gy (%) | 50.62 ± 11.53 | 24.80 ± 4.78 | 0.004* |
| V30Gy (%) | 30.19 ± 5.68 | 20.26 ± 3.86 | 0.003* | |
| V45Gy (cm3) | 201.19 ± 80.81 | 198.10 ± 91.30 | 0.321 | |
| D1% (Gy) | 47.48 ± 0.86 | 46.77 ± 0.16 | 0.082 | |
| Dmean (Gy) | 21.11 ± 3.25 | 11.56 ± 2.26 | 0.000* | |
| Vol. overlap with PTV1 (cm3): 182.74 ± 66.50 (92.58–273.07) | ||||
| Rt Femur | D50% (Gy) | 19.26 ± 1.19 | 19.70 ± 3.24 | 0.776 |
| D1% (Gy) | 43.50 ± 2.49 | 29.84 ± 3.80 | 0.002* | |
| Dmean (Gy) | 19.85 ± 1.07 | 17.86 ± 1.77 | 0.036* | |
| Lt Femur | D50% (Gy) | 18.67 ± 1.22 | 19.56 ± 3.62 | 0.49 |
| D1% (Gy) | 42.46 ± 4.50 | 31.21 ± 3.42 | 0.003* | |
| Dmean (Gy) | 19.38 ± 1.80 | 17.69 ± 2.35 | 0.007* | |
| ID (Gy.L) | ID PTV1 | 222.68 ± 20.96 | 123.58 ± 10.36 | 0.000* |
| ID PTV2 | 37.96 ± 4.88 | 18.75 ± 4.99 | 0.000* | |
Gy(RBE); gray(radiobiological equivalent); VMAT, volumetric modulated arc therapy; PBS, pencil beam scanning; ID, integral dose; Dx, dose received by an organ at risk at a defined volume (x) in percentage; Vx, volume of the organ at risk receiving a defined dose (x) in Gray; *p < 0.05, statistically significant.