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Table 4 Dosimetric evaluation for rectum according to spacer

From: Dosimetric feasibility of moderately hypofractionated/dose escalated radiation therapy for localised prostate cancer with intensity-modulated proton beam therapy using simultaneous integrated boost (SIB-IMPT) and impact of hydrogel prostate-rectum spacer

* Non-spacer group
(8 patients)
Spacer group
(15 patients)
P value
Prostate volume (cc) 66.48 ± 22.07
(41.30–109.35)
57.57 ± 20.78
(25.73–95.96)
0.333
Rectal volume (cc) 191.7 ± 30.9
(154.9–231.1)
172.8 ± 23.1
(135.2–206.9)
0.131
Rectum Dmax 74.15 ± 0.87
(73.00–76.0)
73.15 ± 0.89
(71.02–74.0)
0.013
Rectum Dmean 24.10 ± 7.56
(12.66–36.39)
19.1 ± 4.6
(9.73–25.75)
0.065
Rectum Dmedian 13.44 ± 11.88
(2.13–38.41)
7.4 ± 5.02
(1.6–18.59)
0.238
RV73Gy 0.67 ± 0.58
(0.05–1.53)
0.12 ± 0.13
(0–0.42)
0.007
RV72Gy 3.34 ± 1.89
(1.12–6.66)
1.19 ± 1.0
(0.00–3.04)
0.005
RV70Gy 7.56 ± 2.97
(2.45–10.72)
3.078 ± 2.23
(0.05–6.87)
0.001
RV68.4 Gy (95% of dose) 9.52 ± 3.41
(3.32–12.64)
4.17 ± 2.71
(0.15–8.8)
0.002
RV66Gy 11.95 ± 4.27
(4.27–15.83)
5.67 ± 3.31
(0.37–10.86)
0.003
RV65Gy 12.90 ± 4.57
(4.93–17.69)
6.25 ± 3.52
(0.51–11.63)
0.003
RV62Gy 15.51 ± 5.86
(5.76–3.25)
8.1 ± 4.18
(1.05–14.08)
0.005
RV60Gy 17.11 ± 6.12
(6.46–26.75)
9.49 ± 4.32
(1.82–15.40)
0.005
RV55Gy 20.95 ± 8.1
(7.95–33.46)
13.22 ± 4.74
(3.12–18.74)
0.016
RV50Gy 24.18 ± 9.20
(9.6–38.92)
16.49 ± 5.38
(4.57–22.76)
0.019
RV40Gy 29.96 ± 11.1
(12.97–48.65)
22.15 ± 6.48
(8.26–32.02)
0.056
RV30Gy 35.49 ± 12.51
(16.84–56.85)
27.91 ± 7.49
(12.61–40.32)
0.065
RV20Gy 41.75 ± 13.72
(21.62–64.97)
34.48 ± 8.39
(18.25–48.8)
0.149
RV10Gy 50.42 ± 14.65
(29.74–74.97)
43.85 ± 9.44
(26.67–59.37)
0.231
  1. Significance P value < 0.05 (Bold)
  2. *Dose in Gy; RVX Gy = Percentage of rectal volume received X dose; all result are presented in mean ± SD (range)